diff --git a/Build.PL b/Build.PL
index 0852b4eac..bfdb9d978 100644
--- a/Build.PL
+++ b/Build.PL
@@ -19,7 +19,6 @@ my %prereqs = qw(
     Moo                             1.003001
     POSIX                           0
     Scalar::Util                    0
-    Test::Harness                   0
     Test::More                      0
     Thread::Semaphore               0
     IO::Scalar                      0
@@ -28,9 +27,8 @@ my %prereqs = qw(
 );
 my %recommends = qw(
     Class::XSAccessor               0
-    LWP::UserAgent                  0
-    Net::Bonjour                    0
     XML::SAX::ExpatXS               0
+    Test::Harness                   0
 );
 
 my $sudo    = grep { $_ eq '--sudo' } @ARGV;
@@ -40,14 +38,20 @@ if ($gui) {
     %prereqs = qw(
     Class::Accessor                 0
     Wx                              0.9918
+    Socket                          2.016
     );
     %recommends = qw(
     Growl::GNTP                     0.15
     Wx::GLCanvas                    0
     OpenGL                          0
+    LWP::UserAgent                  0
+    Net::Bonjour                    0
     );
     if ($^O eq 'MSWin32') {
         $recommends{"Win32::TieRegistry"} = 0;
+        
+        # we need an up-to-date Win32::API because older aren't thread-safe (GH #2517)
+        $prereqs{'Win32::API'} = 0.79;
     }
 } elsif ($xs_only) {
     %prereqs = %recommends = ();
@@ -115,7 +119,7 @@ EOF
     foreach my $module (sort keys %modules) {
         my $version = $modules{$module};
         my @cmd = ($cpanm, @cpanm_args);
-        push @cmd, '-f', if $module eq 'OpenGL';  # temporary workaround for upstream bug in test
+        push @cmd, '--notest', if $module eq 'OpenGL';  # temporary workaround for upstream bug in test
         push @cmd, "$module~$version";
         if ($module eq 'XML::SAX::ExpatXS' && $^O eq 'MSWin32') {
             my $mingw = 'C:\dev\CitrusPerl\mingw64';
diff --git a/README.md b/README.md
index 70ec89d1d..ee97e5b65 100644
--- a/README.md
+++ b/README.md
@@ -61,8 +61,8 @@ If you want to compile the source yourself just do the following (checkout
 ```
 $ git clone https://github.com/alexrj/Slic3r.git
 $ cd Slic3r
-$ sudo perl Build.PL
-$ sudo perl Build.PL --gui
+$ perl Build.PL --sudo
+$ perl Build.PL --sudo --gui
 $ ./slic3r.pl
 ```
 
@@ -219,7 +219,8 @@ The author of the Silk icon set is Mark James.
         --end-gcode         Load final G-code from the supplied file. This will overwrite
                             the default commands (turn off temperature [M104 S0],
                             home X axis [G28 X], disable motors [M84]).
-        --layer-gcode       Load layer-change G-code from the supplied file (default: nothing).
+        --before-layer-gcode  Load before-layer-change G-code from the supplied file (default: nothing).
+        --layer-gcode       Load after-layer-change G-code from the supplied file (default: nothing).
         --toolchange-gcode  Load tool-change G-code from the supplied file (default: nothing).
         --seam-position     Position of loop starting points (random/nearest/aligned, default: aligned).
         --external-perimeters-first Reverse perimeter order. (default: no)
@@ -253,6 +254,9 @@ The author of the Silk icon set is Mark James.
                             Spacing between pattern lines (mm, default: 2.5)
         --support-material-angle
                             Support material angle in degrees (range: 0-90, default: 0)
+        --support-material-contact-distance
+                            Vertical distance between object and support material
+                            (0+, default: 0.2)
         --support-material-interface-layers
                             Number of perpendicular layers between support material and object (0+, default: 3)
         --support-material-interface-spacing
@@ -279,8 +283,8 @@ The author of the Silk icon set is Mark James.
     
        Retraction options for multi-extruder setups:
         --retract-length-toolchange
-                            Length of retraction in mm when disabling tool (default: 1)
-        --retract-restart-extra-toolchnage
+                            Length of retraction in mm when disabling tool (default: 10)
+        --retract-restart-extra-toolchange
                             Additional amount of filament in mm to push after
                             switching tool (default: 0)
     
@@ -346,6 +350,7 @@ The author of the Silk icon set is Mark James.
                             Set a different extrusion width for top infill
         --support-material-extrusion-width
                             Set a different extrusion width for support material
+        --infill-overlap    Overlap between infill and perimeters (default: 15%)
         --bridge-flow-ratio Multiplier for extrusion when bridging (> 0, default: 1)
     
        Multiple extruder options:
diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index 2ddb1050f..60d7ac4a5 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -79,7 +79,7 @@ use constant RESOLUTION             => 0.0125;
 use constant SCALED_RESOLUTION      => RESOLUTION / SCALING_FACTOR;
 use constant SMALL_PERIMETER_LENGTH => (6.5 / SCALING_FACTOR) * 2 * PI;
 use constant LOOP_CLIPPING_LENGTH_OVER_NOZZLE_DIAMETER => 0.15;
-use constant INFILL_OVERLAP_OVER_SPACING  => 0.45;
+use constant INFILL_OVERLAP_OVER_SPACING  => 0.3;
 use constant EXTERNAL_INFILL_MARGIN => 3;
 use constant INSET_OVERLAP_TOLERANCE => 0.4;
 
@@ -211,6 +211,7 @@ sub thread_cleanup {
     *Slic3r::Polyline::DESTROY              = sub {};
     *Slic3r::Polyline::Collection::DESTROY  = sub {};
     *Slic3r::Print::DESTROY                 = sub {};
+    *Slic3r::Print::Object::DESTROY         = sub {};
     *Slic3r::Print::Region::DESTROY         = sub {};
     *Slic3r::Surface::DESTROY               = sub {};
     *Slic3r::Surface::Collection::DESTROY   = sub {};
diff --git a/lib/Slic3r/Config.pm b/lib/Slic3r/Config.pm
index 61d4bb97c..e2739c421 100644
--- a/lib/Slic3r/Config.pm
+++ b/lib/Slic3r/Config.pm
@@ -218,6 +218,8 @@ sub validate {
     # --first-layer-height
     die "Invalid value for --first-layer-height\n"
         if $self->first_layer_height !~ /^(?:\d*(?:\.\d+)?)%?$/;
+    die "Invalid value for --first-layer-height\n"
+        if $self->get_value('first_layer_height') <= 0;
     
     # --filament-diameter
     die "Invalid value for --filament-diameter\n"
diff --git a/lib/Slic3r/Fill.pm b/lib/Slic3r/Fill.pm
index 1881d461b..e3acbe551 100644
--- a/lib/Slic3r/Fill.pm
+++ b/lib/Slic3r/Fill.pm
@@ -142,7 +142,7 @@ sub make_fill {
     # we are going to grow such regions by overlapping them with the void (if any)
     # TODO: detect and investigate whether there could be narrow regions without
     # any void neighbors
-    my $distance_between_surfaces = $infill_flow->scaled_spacing * &Slic3r::INFILL_OVERLAP_OVER_SPACING;
+    my $distance_between_surfaces = $infill_flow->scaled_spacing;
     {
         my $collapsed = diff(
             [ map @{$_->expolygon}, @surfaces ],
diff --git a/lib/Slic3r/Fill/Concentric.pm b/lib/Slic3r/Fill/Concentric.pm
index 17f3fa225..1bc9b79f9 100644
--- a/lib/Slic3r/Fill/Concentric.pm
+++ b/lib/Slic3r/Fill/Concentric.pm
@@ -26,9 +26,7 @@ sub fill_surface {
         $self->spacing(unscale $distance);
     }
     
-    # compensate the overlap which is good for rectilinear but harmful for concentric
-    # where the perimeter/infill spacing should be equal to any other loop spacing
-    my @loops = my @last = @{offset(\@$expolygon, -&Slic3r::INFILL_OVERLAP_OVER_SPACING * $min_spacing / 2)};
+    my @loops = my @last = map $_->clone, @$expolygon;
     while (@last) {
         push @loops, @last = @{offset2(\@last, -($distance + 0.5*$min_spacing), +0.5*$min_spacing)};
     }
diff --git a/lib/Slic3r/Fill/Honeycomb.pm b/lib/Slic3r/Fill/Honeycomb.pm
index 0fb47db4d..b0fbd65ff 100644
--- a/lib/Slic3r/Fill/Honeycomb.pm
+++ b/lib/Slic3r/Fill/Honeycomb.pm
@@ -81,7 +81,7 @@ sub fill_surface {
     }
     
     my @paths;
-    if ($params{complete}) {
+    if ($params{complete} || 1) {
         # we were requested to complete each loop;
         # in this case we don't try to make more continuous paths
         @paths = map $_->split_at_first_point,
diff --git a/lib/Slic3r/Fill/Rectilinear.pm b/lib/Slic3r/Fill/Rectilinear.pm
index a50e12b09..b16b0bb0c 100644
--- a/lib/Slic3r/Fill/Rectilinear.pm
+++ b/lib/Slic3r/Fill/Rectilinear.pm
@@ -54,10 +54,21 @@ sub fill_surface {
     # the minimum offset for preventing edge lines from being clipped is scaled_epsilon;
     # however we use a larger offset to support expolygons with slightly skewed sides and 
     # not perfectly straight
-    my @polylines = @{intersection_pl(\@vertical_lines, $expolygon->offset(scale 0.02))};
+    my @polylines = @{intersection_pl(\@vertical_lines, $expolygon->offset(+scale 0.02))};
+    
+    my $extra = $self->_min_spacing * &Slic3r::INFILL_OVERLAP_OVER_SPACING;
+    foreach my $polyline (@polylines) {
+        my ($first_point, $last_point) = @$polyline[0,-1];
+        if ($first_point->y > $last_point->y) { #>
+            ($first_point, $last_point) = ($last_point, $first_point);
+        }
+        $first_point->set_y($first_point->y - $extra);  #--
+        $last_point->set_y($last_point->y + $extra);    #++
+    }
     
     # connect lines
     unless ($params{dont_connect} || !@polylines) {  # prevent calling leftmost_point() on empty collections
+        # offset the expolygon by max(min_spacing/2, extra)
         my ($expolygon_off) = @{$expolygon->offset_ex($self->_min_spacing/2)};
         my $collection = Slic3r::Polyline::Collection->new(@polylines);
         @polylines = ();
diff --git a/lib/Slic3r/Format/STL.pm b/lib/Slic3r/Format/STL.pm
index c9fc303ff..11928d8b2 100644
--- a/lib/Slic3r/Format/STL.pm
+++ b/lib/Slic3r/Format/STL.pm
@@ -14,6 +14,9 @@ sub read_file {
     $mesh->ReadSTLFile($path);
     $mesh->repair;
     
+    die "This STL file couldn't be read because it's empty.\n"
+        if $mesh->facets_count == 0;
+    
     my $model = Slic3r::Model->new;
     
     my $basename = basename($file);
diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index c3bc2dfb4..62a8f2ab5 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -141,7 +141,7 @@ sub extrude_loop {
         my $obj_ptr = 0;
         if (defined $self->layer) {
             $obj_ptr = $self->layer->object->ptr;
-            if (defined $self->_seam_position->{$self->layer->object}) {
+            if (defined $self->_seam_position->{$obj_ptr}) {
                 $last_pos = $self->_seam_position->{$obj_ptr};
             }
         }
@@ -500,11 +500,14 @@ sub pre_toolchange {
     
     # move to the nearest standby point
     if (@{$self->standby_points}) {
-        my $last_pos = $gcodegen->last_pos->clone;
-        $last_pos->translate(scale +$gcodegen->origin->x, scale +$gcodegen->origin->y);  #))
-        my $standby_point = $last_pos->nearest_point($self->standby_points);
-        $standby_point->translate(scale -$gcodegen->origin->x, scale -$gcodegen->origin->y);  #))
-        $gcode .= $gcodegen->travel_to($standby_point, undef, 'move to standby position');
+        # get current position in print coordinates
+        my $pos = Slic3r::Point->new_scale(@{$gcodegen->writer->get_position}[0,1]);
+        
+        my $standby_point = Slic3r::Pointf->new_unscale(@{$pos->nearest_point($self->standby_points)});
+        # We don't call $gcodegen->travel_to() because we don't need retraction (it was already
+        # triggered by the caller) nor avoid_crossing_perimeters and also because the coordinates
+        # of the destination point must not be transformed by origin nor current extruder offset.
+        $gcode .= $gcodegen->writer->travel_to_xy($standby_point, 'move to standby position');
     }
     
     if ($gcodegen->config->standby_temperature_delta != 0) {
diff --git a/lib/Slic3r/GUI.pm b/lib/Slic3r/GUI.pm
index 246c7edb7..af4646745 100644
--- a/lib/Slic3r/GUI.pm
+++ b/lib/Slic3r/GUI.pm
@@ -17,9 +17,9 @@ use Slic3r::GUI::Plater;
 use Slic3r::GUI::Plater::2D;
 use Slic3r::GUI::Plater::2DToolpaths;
 use Slic3r::GUI::Plater::3D;
+use Slic3r::GUI::Plater::3DPreview;
 use Slic3r::GUI::Plater::ObjectPartsPanel;
 use Slic3r::GUI::Plater::ObjectCutDialog;
-use Slic3r::GUI::Plater::ObjectPreviewDialog;
 use Slic3r::GUI::Plater::ObjectSettingsDialog;
 use Slic3r::GUI::Plater::OverrideSettingsPanel;
 use Slic3r::GUI::Preferences;
@@ -29,7 +29,7 @@ use Slic3r::GUI::OptionsGroup::Field;
 use Slic3r::GUI::SimpleTab;
 use Slic3r::GUI::Tab;
 
-our $have_OpenGL = eval "use Slic3r::GUI::PreviewCanvas; 1";
+our $have_OpenGL = eval "use Slic3r::GUI::3DScene; 1";
 our $have_LWP    = eval "use LWP::UserAgent; 1";
 
 use Wx 0.9901 qw(:bitmap :dialog :icon :id :misc :systemsettings :toplevelwindow
@@ -86,9 +86,13 @@ sub OnInit {
     # just checking for existence of $datadir is not enough: it may be an empty directory
     # supplied as argument to --datadir; in that case we should still run the wizard
     my $run_wizard = (-d $enc_datadir && -e "$enc_datadir/slic3r.ini") ? 0 : 1;
-    for ($enc_datadir, "$enc_datadir/print", "$enc_datadir/filament", "$enc_datadir/printer") {
-        mkdir or $self->fatal_error("Slic3r was unable to create its data directory at $_ (errno: $!).")
-            unless -d $_;
+    foreach my $dir ($enc_datadir, "$enc_datadir/print", "$enc_datadir/filament", "$enc_datadir/printer") {
+        next if -d $dir;
+        if (!mkdir $dir) {
+            my $error = "Slic3r was unable to create its data directory at $dir ($!).";
+            warn "$error\n";
+            fatal_error(undef, $error);
+        }
     }
     
     # load settings
@@ -165,22 +169,19 @@ sub catch_error {
 
 # static method accepting a wxWindow object as first parameter
 sub show_error {
-    my $self = shift;
-    my ($message) = @_;
-    Wx::MessageDialog->new($self, $message, 'Error', wxOK | wxICON_ERROR)->ShowModal;
+    my ($parent, $message) = @_;
+    Wx::MessageDialog->new($parent, $message, 'Error', wxOK | wxICON_ERROR)->ShowModal;
 }
 
 # static method accepting a wxWindow object as first parameter
 sub show_info {
-    my $self = shift;
-    my ($message, $title) = @_;
-    Wx::MessageDialog->new($self, $message, $title || 'Notice', wxOK | wxICON_INFORMATION)->ShowModal;
+    my ($parent, $message, $title) = @_;
+    Wx::MessageDialog->new($parent, $message, $title || 'Notice', wxOK | wxICON_INFORMATION)->ShowModal;
 }
 
 # static method accepting a wxWindow object as first parameter
 sub fatal_error {
-    my $self = shift;
-    $self->show_error(@_);
+    show_error(@_);
     exit 1;
 }
 
@@ -220,6 +221,7 @@ sub presets {
     opendir my $dh, Slic3r::encode_path("$Slic3r::GUI::datadir/$section")
         or die "Failed to read directory $Slic3r::GUI::datadir/$section (errno: $!)\n";
     foreach my $file (grep /\.ini$/i, readdir $dh) {
+        $file = Slic3r::decode_path($file);
         my $name = basename($file);
         $name =~ s/\.ini$//;
         $presets{$name} = "$Slic3r::GUI::datadir/$section/$file";
diff --git a/lib/Slic3r/GUI/PreviewCanvas.pm b/lib/Slic3r/GUI/3DScene.pm
similarity index 63%
rename from lib/Slic3r/GUI/PreviewCanvas.pm
rename to lib/Slic3r/GUI/3DScene.pm
index 6872af989..2974179ca 100644
--- a/lib/Slic3r/GUI/PreviewCanvas.pm
+++ b/lib/Slic3r/GUI/3DScene.pm
@@ -1,4 +1,4 @@
-package Slic3r::GUI::PreviewCanvas;
+package Slic3r::GUI::3DScene::Base;
 use strict;
 use warnings;
 
@@ -13,6 +13,7 @@ use Slic3r::Geometry::Clipper qw(offset_ex intersection_pl);
 use Wx::GLCanvas qw(:all);
  
 __PACKAGE__->mk_accessors( qw(_quat _dirty init
+                              enable_cutting
                               enable_picking
                               enable_moving
                               on_hover
@@ -21,7 +22,6 @@ __PACKAGE__->mk_accessors( qw(_quat _dirty init
                               on_right_click
                               on_move
                               volumes
-                              print
                               _sphi _stheta
                               cutting_plane_z
                               cut_lines_vertices
@@ -40,12 +40,12 @@ __PACKAGE__->mk_accessors( qw(_quat _dirty init
                               _zoom
                               ) );
 
-use constant TRACKBALLSIZE => 0.8;
+use constant TRACKBALLSIZE  => 0.8;
 use constant TURNTABLE_MODE => 1;
 use constant GROUND_Z       => -0.02;
+use constant DEFAULT_COLOR  => [1,1,0];
 use constant SELECTED_COLOR => [0,1,0,1];
 use constant HOVER_COLOR    => [0.4,0.9,0,1];
-use constant COLORS => [ [1,1,0], [1,0.5,0.5], [0.5,1,0.5], [0.5,0.5,1] ];
 
 # make OpenGL::Array thread-safe
 {
@@ -135,6 +135,17 @@ sub mouse_event {
         if ($self->enable_picking) {
             $self->deselect_volumes;
             $self->select_volume($volume_idx);
+            
+            if ($volume_idx != -1) {
+                my $group_id = $self->volumes->[$volume_idx]->select_group_id;
+                my @volumes;
+                if ($group_id != -1) {
+                    $self->select_volume($_)
+                        for grep $self->volumes->[$_]->select_group_id == $group_id,
+                        0..$#{$self->volumes};
+                }
+            }
+            
             $self->Refresh;
         }
         
@@ -163,8 +174,13 @@ sub mouse_event {
         # get volume being dragged
         my $volume = $self->volumes->[$self->_drag_volume_idx];
         
-        # get all volumes belonging to the same group but only having the same instance_idx
-        my @volumes = grep $_->group_id == $volume->group_id && $_->instance_idx == $volume->instance_idx, @{$self->volumes};
+        # get all volumes belonging to the same group, if any
+        my @volumes;
+        if ($volume->drag_group_id == -1) {
+            @volumes = ($volume);
+        } else {
+            @volumes = grep $_->drag_group_id == $volume->drag_group_id, @{$self->volumes};
+        }
         
         # apply new temporary volume origin and ignore Z
         $_->origin->translate($vector->x, $vector->y, 0) for @volumes; #,,
@@ -209,8 +225,17 @@ sub mouse_event {
             $self->_drag_start_xy($pos);
         }
     } elsif ($e->LeftUp || $e->MiddleUp || $e->RightUp) {
-        if ($self->on_move && defined $self->_drag_volume_idx) {
-            $self->on_move->($self->_drag_volume_idx) if $self->_dragged;
+        if ($self->on_move && defined($self->_drag_volume_idx) && $self->_dragged) {
+            # get all volumes belonging to the same group, if any
+            my @volume_idxs;
+            my $group_id = $self->volumes->[$self->_drag_volume_idx]->drag_group_id;
+            if ($group_id == -1) {
+                @volume_idxs = ($self->_drag_volume_idx);
+            } else {
+                @volume_idxs = grep $self->volumes->[$_]->drag_group_id == $group_id,
+                    0..$#{$self->volumes};
+            }
+            $self->on_move->(@volume_idxs);
         }
         $self->_drag_volume_idx(undef);
         $self->_drag_start_pos(undef);
@@ -256,7 +281,7 @@ sub zoom_to_volume {
     my ($self, $volume_idx) = @_;
     
     my $volume = $self->volumes->[$volume_idx];
-    my $bb = $volume->bounding_box;
+    my $bb = $volume->transformed_bounding_box;
     $self->zoom_to_bounding_box($bb);
 }
 
@@ -269,7 +294,7 @@ sub volumes_bounding_box {
     my ($self) = @_;
     
     my $bb = Slic3r::Geometry::BoundingBoxf3->new;
-    $bb->merge($_->bounding_box) for @{$self->volumes};
+    $bb->merge($_->transformed_bounding_box) for @{$self->volumes};
     return $bb;
 }
 
@@ -348,59 +373,6 @@ sub set_bed_shape {
     $self->origin(Slic3r::Pointf->new(0,0));
 }
 
-sub load_object {
-    my ($self, $object, $all_instances) = @_;
-    
-    my $z_min = $object->raw_bounding_box->z_min;
-    
-    # color mesh(es) by material
-    my @materials = ();
-    
-    # sort volumes: non-modifiers first
-    my @volumes = sort { ($a->modifier // 0) <=> ($b->modifier // 0) } @{$object->volumes};
-    my @volumes_idx = ();
-    my $group_id = $#{$self->volumes} + 1;
-    foreach my $volume (@volumes) {
-        my @instance_idxs = $all_instances ? (0..$#{$object->instances}) : (0);
-        foreach my $instance_idx (@instance_idxs) {
-            my $instance = $object->instances->[$instance_idx];
-            my $mesh = $volume->mesh->clone;
-            $instance->transform_mesh($mesh);
-            
-            my $material_id = $volume->material_id // '_';
-            my $color_idx = first { $materials[$_] eq $material_id } 0..$#materials;
-            if (!defined $color_idx) {
-                push @materials, $material_id;
-                $color_idx = $#materials;
-            }
-        
-            my $color = [ @{COLORS->[ $color_idx % scalar(@{&COLORS}) ]} ];
-            push @$color, $volume->modifier ? 0.5 : 1;
-            push @{$self->volumes}, my $v = Slic3r::GUI::PreviewCanvas::Volume->new(
-                group_id        => $group_id,
-                instance_idx    => $instance_idx,
-                mesh            => $mesh,
-                color           => $color,
-                origin          => Slic3r::Pointf3->new(0,0,-$z_min),
-            );
-            push @volumes_idx, $#{$self->volumes};
-        
-            {
-                my $vertices = $mesh->vertices;
-                my @verts = map @{ $vertices->[$_] }, map @$_, @{$mesh->facets};
-                $v->verts(OpenGL::Array->new_list(GL_FLOAT, @verts));
-            }
-        
-            {
-                my @norms = map { @$_, @$_, @$_ } @{$mesh->normals};
-                $v->norms(OpenGL::Array->new_list(GL_FLOAT, @norms));
-            }
-        }
-    }
-    
-    return @volumes_idx;
-}
-
 sub deselect_volumes {
     my ($self) = @_;
     $_->selected(0) for @{$self->volumes};
@@ -422,6 +394,7 @@ sub SetCuttingPlane {
     my @verts = ();
     foreach my $volume (@{$self->volumes}) {
         foreach my $volume (@{$self->volumes}) {
+            next if !$volume->mesh;
             my $expolygons = $volume->mesh->slice([ $z - $volume->origin->z ])->[0];
             $expolygons = offset_ex([ map @$_, @$expolygons ], scale 0.1);
             
@@ -698,7 +671,13 @@ sub Render {
             $_->hover(0) for @{$self->volumes};
             if ($volume_idx <= $#{$self->volumes}) {
                 $self->_hover_volume_idx($volume_idx);
+                
                 $self->volumes->[$volume_idx]->hover(1);
+                my $group_id = $self->volumes->[$volume_idx]->select_group_id;
+                if ($group_id != -1) {
+                    $_->hover(1) for grep { $_->select_group_id == $group_id } @{$self->volumes};
+                }
+                
                 $self->on_hover->($volume_idx) if $self->on_hover;
             }
         }
@@ -833,73 +812,6 @@ sub draw_volumes {
     glEnable(GL_BLEND);
     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
     
-    if (defined($self->print) && !$fakecolor) {
-        my $tess = gluNewTess();
-        gluTessCallback($tess, GLU_TESS_BEGIN,     'DEFAULT');
-        gluTessCallback($tess, GLU_TESS_END,       'DEFAULT');
-        gluTessCallback($tess, GLU_TESS_VERTEX,    'DEFAULT');
-        gluTessCallback($tess, GLU_TESS_COMBINE,   'DEFAULT');
-        gluTessCallback($tess, GLU_TESS_ERROR,     'DEFAULT');
-        gluTessCallback($tess, GLU_TESS_EDGE_FLAG, 'DEFAULT');
-        
-        foreach my $object (@{$self->print->objects}) {
-            foreach my $layer (@{$object->layers}) {
-                my $gap = 0;
-                my $top_z = $layer->print_z;
-                my $bottom_z = $layer->print_z - $layer->height + $gap;
-            
-                foreach my $copy (@{ $object->_shifted_copies }) {
-                    glPushMatrix();
-                    glTranslatef(map unscale($_), @$copy, 0);
-                    
-                    foreach my $slice (@{$layer->slices}) {
-                        glColor3f(@{COLORS->[0]});
-                        gluTessBeginPolygon($tess);
-                        glNormal3f(0,0,1);
-                        foreach my $polygon (@$slice) {
-                            gluTessBeginContour($tess);
-                            gluTessVertex_p($tess, (map unscale($_), @$_), $layer->print_z) for @$polygon;
-                            gluTessEndContour($tess);
-                        }
-                        gluTessEndPolygon($tess);
-                        
-                        foreach my $polygon (@$slice) {
-                            foreach my $line (@{$polygon->lines}) {
-                                if (0) {
-                                    glLineWidth(1);
-                                    glColor3f(0,0,0);
-                                    glBegin(GL_LINES);
-                                    glVertex3f((map unscale($_), @{$line->a}), $bottom_z);
-                                    glVertex3f((map unscale($_), @{$line->b}), $bottom_z);
-                                    glEnd();
-                                }
-                                
-                                glLineWidth(0);
-                                glColor3f(@{COLORS->[0]});
-                                glBegin(GL_QUADS);
-                                # We'll use this for the middle normal when using 4 quads:
-                                #my $xy_normal = $line->normal;
-                                #$_xynormal->scale(1/$line->length);
-                                glNormal3f(0,0,-1);
-                                glVertex3f((map unscale($_), @{$line->a}), $bottom_z);
-                                glVertex3f((map unscale($_), @{$line->b}), $bottom_z);
-                                glNormal3f(0,0,1);
-                                glVertex3f((map unscale($_), @{$line->b}), $top_z);
-                                glVertex3f((map unscale($_), @{$line->a}), $top_z);
-                                glEnd();
-                            }
-                        }
-                    }
-                    
-                    glPopMatrix();  # copy
-                }
-            }
-        }
-        
-        gluDeleteTess($tess);
-        return;
-    }
-    
     glEnableClientState(GL_VERTEX_ARRAY);
     glEnableClientState(GL_NORMAL_ARRAY);
     
@@ -908,10 +820,6 @@ sub draw_volumes {
         glPushMatrix();
         glTranslatef(@{$volume->origin});
         
-        glVertexPointer_p(3, $volume->verts);
-        
-        glCullFace(GL_BACK);
-        glNormalPointer_p($volume->norms);
         if ($fakecolor) {
             my $r = ($volume_idx & 0x000000FF) >>  0;
             my $g = ($volume_idx & 0x0000FF00) >>  8;
@@ -924,7 +832,49 @@ sub draw_volumes {
         } else {
             glColor4f(@{ $volume->color });
         }
-        glDrawArrays(GL_TRIANGLES, 0, $volume->verts->elements / 3);
+        
+        my @sorted_z = ();
+        my ($min_z, $max_z);
+        if ($volume->range && $volume->offsets) {
+            @sorted_z = sort { $a <=> $b } keys %{$volume->offsets};
+            
+            ($min_z, $max_z) = @{$volume->range};
+            $min_z = first { $_ >= $min_z } @sorted_z;
+            $max_z = first { $_ > $max_z }  @sorted_z;
+        }
+        
+        glCullFace(GL_BACK);
+        if ($volume->qverts) {
+            my ($min_offset, $max_offset);
+            if (defined $min_z) {
+                $min_offset = $volume->offsets->{$min_z}->[0];
+            }
+            if (defined $max_z) {
+                $max_offset = $volume->offsets->{$max_z}->[0];
+            }
+            $min_offset //= 0;
+            $max_offset //= $volume->qverts->size;
+            
+            glVertexPointer_c(3, GL_FLOAT, 0, $volume->qverts->verts_ptr);
+            glNormalPointer_c(GL_FLOAT, 0, $volume->qverts->norms_ptr);
+            glDrawArrays(GL_QUADS, $min_offset / 3, ($max_offset-$min_offset) / 3);
+        }
+        
+        if ($volume->tverts) {
+            my ($min_offset, $max_offset);
+            if (defined $min_z) {
+                $min_offset = $volume->offsets->{$min_z}->[1];
+            }
+            if (defined $max_z) {
+                $max_offset = $volume->offsets->{$max_z}->[1];
+            }
+            $min_offset //= 0;
+            $max_offset //= $volume->tverts->size;
+            
+            glVertexPointer_c(3, GL_FLOAT, 0, $volume->tverts->verts_ptr);
+            glNormalPointer_c(GL_FLOAT, 0, $volume->tverts->norms_ptr);
+            glDrawArrays(GL_TRIANGLES, $min_offset / 3, ($max_offset-$min_offset) / 3);
+        }
         
         glPopMatrix();
     }
@@ -940,25 +890,352 @@ sub draw_volumes {
     glDisableClientState(GL_VERTEX_ARRAY);
 }
 
-package Slic3r::GUI::PreviewCanvas::Volume;
+package Slic3r::GUI::3DScene::Volume;
 use Moo;
 
-has 'mesh'          => (is => 'ro', required => 1);
-has 'color'         => (is => 'ro', required => 1);
-has 'group_id'      => (is => 'ro', required => 1);
-has 'instance_idx'  => (is => 'ro', default => sub { 0 });
-has 'origin'        => (is => 'rw', default => sub { Slic3r::Pointf3->new(0,0,0) });
-has 'verts'         => (is => 'rw');
-has 'norms'         => (is => 'rw');
-has 'selected'      => (is => 'rw', default => sub { 0 });
-has 'hover'         => (is => 'rw', default => sub { 0 });
+has 'bounding_box'      => (is => 'ro', required => 1);
+has 'origin'            => (is => 'rw', default => sub { Slic3r::Pointf3->new(0,0,0) });
+has 'color'             => (is => 'ro', required => 1);
+has 'select_group_id'   => (is => 'rw', default => sub { -1 });
+has 'drag_group_id'     => (is => 'rw', default => sub { -1 });
+has 'selected'          => (is => 'rw', default => sub { 0 });
+has 'hover'             => (is => 'rw', default => sub { 0 });
+has 'range'             => (is => 'rw');
 
-sub bounding_box {
+# geometric data
+has 'qverts'            => (is => 'rw');  # GLVertexArray object
+has 'tverts'            => (is => 'rw');  # GLVertexArray object
+has 'mesh'              => (is => 'rw');  # only required for cut contours
+has 'offsets'           => (is => 'rw');  # [ z => [ qverts_idx, tverts_idx ] ]
+
+sub transformed_bounding_box {
     my ($self) = @_;
     
-    my $bb = $self->mesh->bounding_box;
+    my $bb = $self->bounding_box;
     $bb->translate(@{$self->origin});
     return $bb;
 }
 
+package Slic3r::GUI::3DScene;
+use base qw(Slic3r::GUI::3DScene::Base);
+
+use OpenGL qw(:glconstants :gluconstants :glufunctions);
+use List::Util qw(first);
+use Slic3r::Geometry qw(scale unscale epsilon);
+use Slic3r::Print::State ':steps';
+
+use constant COLORS => [ [1,1,0,1], [1,0.5,0.5,1], [0.5,1,0.5,1], [0.5,0.5,1,1] ];
+
+__PACKAGE__->mk_accessors(qw(
+    color_by
+    select_by
+    drag_by
+    volumes_by_object
+    _objects_by_volumes
+));
+
+sub new {
+    my $class = shift;
+    
+    my $self = $class->SUPER::new(@_);
+    $self->color_by('volume');      # object | volume
+    $self->select_by('object');     # object | volume | instance
+    $self->drag_by('instance');     # object | instance
+    $self->volumes_by_object({});   # obj_idx => [ volume_idx, volume_idx ... ]
+    $self->_objects_by_volumes({}); # volume_idx => [ obj_idx, instance_idx ]
+    
+    return $self;
+}
+
+sub load_object {
+    my ($self, $model, $obj_idx, $instance_idxs) = @_;
+    
+    my $model_object;
+    if ($model->isa('Slic3r::Model::Object')) {
+        $model_object = $model;
+        $model = $model_object->model;
+        $obj_idx = 0;
+    } else {
+        $model_object = $model->get_object($obj_idx);
+    }
+    
+    $instance_idxs ||= [0..$#{$model_object->instances}];
+    
+    my @volumes_idx = ();
+    foreach my $volume_idx (0..$#{$model_object->volumes}) {
+        my $volume = $model_object->volumes->[$volume_idx];
+        foreach my $instance_idx (@$instance_idxs) {
+            my $instance = $model_object->instances->[$instance_idx];
+            my $mesh = $volume->mesh->clone;
+            $instance->transform_mesh($mesh);
+            
+            my $color_idx;
+            if ($self->color_by eq 'volume') {
+                $color_idx = $volume_idx;
+            } elsif ($self->color_by eq 'object') {
+                $color_idx = $obj_idx;
+            }
+        
+            my $color = [ @{COLORS->[ $color_idx % scalar(@{&COLORS}) ]} ];
+            $color->[3] = $volume->modifier ? 0.5 : 1;
+            push @{$self->volumes}, my $v = Slic3r::GUI::3DScene::Volume->new(
+                bounding_box    => $mesh->bounding_box,
+                color           => $color,
+            );
+            $v->mesh($mesh) if $self->enable_cutting;
+            if ($self->select_by eq 'object') {
+                $v->select_group_id($obj_idx*1000000);
+            } elsif ($self->select_by eq 'volume') {
+                $v->select_group_id($obj_idx*1000000 + $volume_idx*1000);
+            } elsif ($self->select_by eq 'instance') {
+                $v->select_group_id($obj_idx*1000000 + $volume_idx*1000 + $instance_idx);
+            }
+            if ($self->drag_by eq 'object') {
+                $v->drag_group_id($obj_idx*1000);
+            } elsif ($self->drag_by eq 'instance') {
+                $v->drag_group_id($obj_idx*1000 + $instance_idx);
+            }
+            push @volumes_idx, my $scene_volume_idx = $#{$self->volumes};
+            $self->_objects_by_volumes->{$scene_volume_idx} = [ $obj_idx, $volume_idx, $instance_idx ];
+            
+            my $verts = Slic3r::GUI::_3DScene::GLVertexArray->new;
+            $verts->load_mesh($mesh);
+            $v->tverts($verts);
+        }
+    }
+    
+    $self->volumes_by_object->{$obj_idx} = [@volumes_idx];
+    return @volumes_idx;
+}
+
+sub load_print_object_slices {
+    my ($self, $object) = @_;
+    
+    my @verts = ();
+    my @norms = ();
+    my @quad_verts = ();
+    my @quad_norms = ();
+    foreach my $layer (@{$object->layers}) {
+        my $gap = 0;
+        my $top_z = $layer->print_z;
+        my $bottom_z = $layer->print_z - $layer->height + $gap;
+    
+        foreach my $copy (@{ $object->_shifted_copies }) {
+            {
+                my @expolygons = map $_->clone, @{$layer->slices};
+                $_->translate(@$copy) for @expolygons;
+                $self->_expolygons_to_verts(\@expolygons, $layer->print_z, \@verts, \@norms);
+            }
+            foreach my $slice (@{$layer->slices}) {
+                foreach my $polygon (@$slice) {
+                    foreach my $line (@{$polygon->lines}) {
+                        $line->translate(@$copy);
+                        
+                        push @quad_norms, (0,0,-1), (0,0,-1);
+                        push @quad_verts, (map unscale($_), @{$line->a}), $bottom_z;
+                        push @quad_verts, (map unscale($_), @{$line->b}), $bottom_z;
+                        push @quad_norms, (0,0,1), (0,0,1);
+                        push @quad_verts, (map unscale($_), @{$line->b}), $top_z;
+                        push @quad_verts, (map unscale($_), @{$line->a}), $top_z;
+                        
+                        # We'll use this for the middle normal when using 4 quads:
+                        #my $xy_normal = $line->normal;
+                        #$_xynormal->scale(1/$line->length);
+                    }
+                }
+            }
+        }
+    }
+    
+    my $obb = $object->bounding_box;
+    my $bb = Slic3r::Geometry::BoundingBoxf3->new;
+    $bb->merge_point(Slic3r::Pointf3->new_unscale(@{$obb->min_point}, 0));
+    $bb->merge_point(Slic3r::Pointf3->new_unscale(@{$obb->max_point}, $object->size->z));
+    
+    push @{$self->volumes}, my $v = Slic3r::GUI::3DScene::Volume->new(
+        bounding_box    => $bb,
+        color           => COLORS->[0],
+        verts           => OpenGL::Array->new_list(GL_FLOAT, @verts),
+        norms           => OpenGL::Array->new_list(GL_FLOAT, @norms),
+        quad_verts      => OpenGL::Array->new_list(GL_FLOAT, @quad_verts),
+        quad_norms      => OpenGL::Array->new_list(GL_FLOAT, @quad_norms),
+    );
+}
+
+sub load_print_object_toolpaths {
+    my ($self, $object) = @_;
+    
+    my $perim_qverts    = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    my $perim_tverts    = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    my $infill_qverts   = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    my $infill_tverts   = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    my $support_qverts  = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    my $support_tverts  = Slic3r::GUI::_3DScene::GLVertexArray->new;
+    
+    my %perim_offsets   = ();  # print_z => [ qverts, tverts ]
+    my %infill_offsets  = ();
+    my %support_offsets = ();
+    
+    # order layers by print_z
+    my @layers = sort { $a->print_z <=> $b->print_z }
+        @{$object->layers}, @{$object->support_layers};
+    
+    foreach my $layer (@layers) {
+        my $top_z = $layer->print_z;
+        
+        if (!exists $perim_offsets{$top_z}) {
+            $perim_offsets{$top_z} = [
+                $perim_qverts->size, $perim_tverts->size,
+            ];
+            $infill_offsets{$top_z} = [
+                $infill_qverts->size, $infill_tverts->size,
+            ];
+            $support_offsets{$top_z} = [
+                $support_qverts->size, $support_tverts->size,
+            ];
+        }
+        
+        foreach my $copy (@{ $object->_shifted_copies }) {
+            foreach my $layerm (@{$layer->regions}) {
+                if ($object->step_done(STEP_PERIMETERS)) {
+                    $self->_extrusionentity_to_verts($layerm->perimeters, $top_z, $copy,
+                        $perim_qverts, $perim_tverts);
+                }
+                
+                if ($object->step_done(STEP_INFILL)) {
+                    $self->_extrusionentity_to_verts($layerm->fills, $top_z, $copy,
+                        $infill_qverts, $infill_tverts);
+                }
+            }
+            
+            if ($layer->isa('Slic3r::Layer::Support') && $object->step_done(STEP_SUPPORTMATERIAL)) {
+                $self->_extrusionentity_to_verts($layer->support_fills, $top_z, $copy,
+                    $support_qverts, $support_tverts);
+                
+                $self->_extrusionentity_to_verts($layer->support_interface_fills, $top_z, $copy,
+                    $support_qverts, $support_tverts);
+            }
+        }
+    }
+    
+    my $obb = $object->bounding_box;
+    my $bb = Slic3r::Geometry::BoundingBoxf3->new;
+    foreach my $copy (@{ $object->_shifted_copies }) {
+        my $cbb = $obb->clone;
+        $cbb->translate(@$copy);
+        $bb->merge_point(Slic3r::Pointf3->new_unscale(@{$cbb->min_point}, 0));
+        $bb->merge_point(Slic3r::Pointf3->new_unscale(@{$cbb->max_point}, $object->size->z));
+    }
+    
+    push @{$self->volumes}, Slic3r::GUI::3DScene::Volume->new(
+        bounding_box    => $bb,
+        color           => COLORS->[0],
+        qverts          => $perim_qverts,
+        tverts          => $perim_tverts,
+        offsets         => { %perim_offsets },
+    );
+    
+    push @{$self->volumes}, Slic3r::GUI::3DScene::Volume->new(
+        bounding_box    => $bb,
+        color           => COLORS->[1],
+        qverts          => $infill_qverts,
+        tverts          => $infill_tverts,
+        offsets         => { %infill_offsets },
+    );
+    
+    push @{$self->volumes}, Slic3r::GUI::3DScene::Volume->new(
+        bounding_box    => $bb,
+        color           => COLORS->[2],
+        qverts          => $support_qverts,
+        tverts          => $support_tverts,
+        offsets         => { %support_offsets },
+    );
+}
+
+sub set_toolpaths_range {
+    my ($self, $min_z, $max_z) = @_;
+    
+    foreach my $volume (@{$self->volumes}) {
+        $volume->range([ $min_z, $max_z ]);
+    }
+}
+
+sub _expolygons_to_verts {
+    my ($self, $expolygons, $z, $verts, $norms) = @_;
+    
+    my $tess = gluNewTess();
+    gluTessCallback($tess, GLU_TESS_BEGIN,     'DEFAULT');
+    gluTessCallback($tess, GLU_TESS_END,       'DEFAULT');
+    gluTessCallback($tess, GLU_TESS_VERTEX, sub {
+        my ($x, $y, $z) = @_;
+        push @$verts, $x, $y, $z;
+        push @$norms, (0,0,1), (0,0,1), (0,0,1);
+    });
+    gluTessCallback($tess, GLU_TESS_COMBINE,   'DEFAULT');
+    gluTessCallback($tess, GLU_TESS_ERROR,     'DEFAULT');
+    gluTessCallback($tess, GLU_TESS_EDGE_FLAG, 'DEFAULT');
+    
+    foreach my $expolygon (@$expolygons) {
+        gluTessBeginPolygon($tess);
+        foreach my $polygon (@$expolygon) {
+            gluTessBeginContour($tess);
+            gluTessVertex_p($tess, (map unscale($_), @$_), $z) for @$polygon;
+            gluTessEndContour($tess);
+        }
+        gluTessEndPolygon($tess);
+    }
+    
+    gluDeleteTess($tess);
+}
+
+sub _extrusionentity_to_verts {
+    my ($self, $entity, $top_z, $copy, $qverts, $tverts) = @_;
+    
+    my ($lines, $widths, $heights, $closed);
+    if ($entity->isa('Slic3r::ExtrusionPath::Collection')) {
+        $self->_extrusionentity_to_verts($_, $top_z, $copy, $qverts, $tverts)
+            for @$entity;
+        return;
+    } elsif ($entity->isa('Slic3r::ExtrusionPath')) {
+        my $polyline = $entity->polyline->clone;
+        $polyline->remove_duplicate_points;
+        $polyline->translate(@$copy);
+        $lines = $polyline->lines;
+        $widths = [ map $entity->width, 0..$#$lines ];
+        $heights = [ map $entity->height, 0..$#$lines ];
+        $closed = 0;
+    } else {
+        $lines   = [];
+        $widths  = [];
+        $heights = [];
+        $closed  = 1;
+        foreach my $path (@$entity) {
+            my $polyline = $path->polyline->clone;
+            $polyline->remove_duplicate_points;
+            $polyline->translate(@$copy);
+            my $path_lines = $polyline->lines;
+            push @$lines, @$path_lines;
+            push @$widths, map $path->width, 0..$#$path_lines;
+            push @$heights, map $path->height, 0..$#$path_lines;
+        }
+    }
+    Slic3r::GUI::_3DScene::_extrusionentity_to_verts_do($lines, $widths, $heights,
+        $closed, $top_z, $copy, $qverts, $tverts);
+}
+
+sub object_idx {
+    my ($self, $volume_idx) = @_;
+    return $self->_objects_by_volumes->{$volume_idx}[0];
+}
+
+sub volume_idx {
+    my ($self, $volume_idx) = @_;
+    return $self->_objects_by_volumes->{$volume_idx}[1];
+}
+
+sub instance_idx {
+    my ($self, $volume_idx) = @_;
+    return $self->_objects_by_volumes->{$volume_idx}[2];
+}
+
 1;
diff --git a/lib/Slic3r/GUI/BonjourBrowser.pm b/lib/Slic3r/GUI/BonjourBrowser.pm
index 281277768..21966d6e8 100644
--- a/lib/Slic3r/GUI/BonjourBrowser.pm
+++ b/lib/Slic3r/GUI/BonjourBrowser.pm
@@ -47,5 +47,9 @@ sub GetValue {
     my ($self) = @_;
     return $self->{devices}[ $self->{choice}->GetSelection ]->address;
 }
+sub GetPort {
+    my ($self) = @_;
+    return $self->{devices}[ $self->{choice}->GetSelection ]->port;
+}
 
 1;
diff --git a/lib/Slic3r/GUI/MainFrame.pm b/lib/Slic3r/GUI/MainFrame.pm
index 91f2bf859..fa4419d0f 100644
--- a/lib/Slic3r/GUI/MainFrame.pm
+++ b/lib/Slic3r/GUI/MainFrame.pm
@@ -47,8 +47,14 @@ sub new {
         $self->Fit;
         $self->SetMinSize([760, 490]);
         if (defined $Slic3r::GUI::Settings->{_}{main_frame_size}) {
-            $self->SetSize([ split ',', $Slic3r::GUI::Settings->{_}{main_frame_size}, 2 ]);
-            $self->Move([ split ',', $Slic3r::GUI::Settings->{_}{main_frame_pos}, 2 ]);
+            my $size = [ split ',', $Slic3r::GUI::Settings->{_}{main_frame_size}, 2 ];
+            $self->SetSize($size);
+            
+            my $display = Wx::Display->new->GetClientArea();
+            my $pos = [ split ',', $Slic3r::GUI::Settings->{_}{main_frame_pos}, 2 ];
+            if (($pos->[X] + $size->[X]/2) < $display->GetRight && ($pos->[Y] + $size->[Y]/2) < $display->GetBottom) {
+                $self->Move($pos);
+            }
             $self->Maximize(1) if $Slic3r::GUI::Settings->{_}{main_frame_maximized};
         } else {
             $self->SetSize($self->GetMinSize);
diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index c5af0dc10..1511010c5 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -11,7 +11,7 @@ use Wx qw(:button :cursor :dialog :filedialog :keycode :icon :font :id :listctrl
     :panel :sizer :toolbar :window wxTheApp :notebook);
 use Wx::Event qw(EVT_BUTTON EVT_COMMAND EVT_KEY_DOWN EVT_LIST_ITEM_ACTIVATED 
     EVT_LIST_ITEM_DESELECTED EVT_LIST_ITEM_SELECTED EVT_MOUSE_EVENTS EVT_PAINT EVT_TOOL 
-    EVT_CHOICE EVT_TIMER);
+    EVT_CHOICE EVT_TIMER EVT_NOTEBOOK_PAGE_CHANGED);
 use base 'Wx::Panel';
 
 use constant TB_ADD             => &Wx::NewId;
@@ -28,7 +28,6 @@ use constant TB_SCALE   => &Wx::NewId;
 use constant TB_SPLIT   => &Wx::NewId;
 use constant TB_CUT     => &Wx::NewId;
 use constant TB_SETTINGS => &Wx::NewId;
-use constant CONFIG_TIMER_ID => &Wx::NewId;
 
 # package variables to avoid passing lexicals to threads
 our $THUMBNAIL_DONE_EVENT    : shared = Wx::NewEventType;
@@ -53,8 +52,6 @@ sub new {
     $self->{model} = Slic3r::Model->new;
     $self->{print} = Slic3r::Print->new;
     $self->{objects} = [];
-    $self->{apply_config_timer} = Wx::Timer->new($self, CONFIG_TIMER_ID)
-        if $Slic3r::have_threads;
     
     $self->{print}->set_status_cb(sub {
         my ($percent, $message) = @_;
@@ -87,32 +84,47 @@ sub new {
         $canvas->PopupMenu($menu, $click_pos);
         $menu->Destroy;
     };
-    my $on_instance_moved = sub {
-        my ($obj_idx, $instance_idx) = @_;
+    my $on_instances_moved = sub {
         $self->update;
     };
     
+    # Initialize 3D plater
+    if ($Slic3r::GUI::have_OpenGL) {
+        $self->{canvas3D} = Slic3r::GUI::Plater::3D->new($self->{preview_notebook}, $self->{objects}, $self->{model}, $self->{config});
+        $self->{preview_notebook}->AddPage($self->{canvas3D}, '3D');
+        $self->{canvas3D}->set_on_select_object($on_select_object);
+        $self->{canvas3D}->set_on_double_click($on_double_click);
+        $self->{canvas3D}->set_on_right_click(sub { $on_right_click->($self->{canvas3D}, @_); });
+        $self->{canvas3D}->set_on_instances_moved($on_instances_moved);
+    }
+    
     # Initialize 2D preview canvas
     $self->{canvas} = Slic3r::GUI::Plater::2D->new($self->{preview_notebook}, wxDefaultSize, $self->{objects}, $self->{model}, $self->{config});
     $self->{preview_notebook}->AddPage($self->{canvas}, '2D');
     $self->{canvas}->on_select_object($on_select_object);
     $self->{canvas}->on_double_click($on_double_click);
     $self->{canvas}->on_right_click(sub { $on_right_click->($self->{canvas}, @_); });
-    $self->{canvas}->on_instance_moved($on_instance_moved);
+    $self->{canvas}->on_instances_moved($on_instances_moved);
     
-    # Initialize 3D preview and toolpaths preview
+    # Initialize 3D toolpaths preview
     if ($Slic3r::GUI::have_OpenGL) {
-        $self->{canvas3D} = Slic3r::GUI::Plater::3D->new($self->{preview_notebook}, $self->{objects}, $self->{model}, $self->{config});
-        $self->{preview_notebook}->AddPage($self->{canvas3D}, '3D');
-        $self->{canvas3D}->set_on_select_object($on_select_object);
-        $self->{canvas3D}->set_on_double_click($on_double_click);
-        $self->{canvas3D}->set_on_right_click(sub { $on_right_click->($self->{canvas3D}, @_); });
-        $self->{canvas3D}->set_on_instance_moved($on_instance_moved);
-        
-        $self->{toolpaths2D} = Slic3r::GUI::Plater::2DToolpaths->new($self->{preview_notebook}, $self->{print});
-        $self->{preview_notebook}->AddPage($self->{toolpaths2D}, 'Preview');
+        $self->{preview3D} = Slic3r::GUI::Plater::3DPreview->new($self->{preview_notebook}, $self->{print});
+        $self->{preview_notebook}->AddPage($self->{preview3D}, 'Preview');
+        $self->{preview3D_page_idx} = $self->{preview_notebook}->GetPageCount-1;
     }
     
+    # Initialize toolpaths preview
+    if ($Slic3r::GUI::have_OpenGL) {
+        $self->{toolpaths2D} = Slic3r::GUI::Plater::2DToolpaths->new($self->{preview_notebook}, $self->{print});
+        $self->{preview_notebook}->AddPage($self->{toolpaths2D}, 'Layers');
+    }
+    
+    EVT_NOTEBOOK_PAGE_CHANGED($self, $self->{preview_notebook}, sub {
+        if ($self->{preview_notebook}->GetSelection == $self->{preview3D_page_idx}) {
+            $self->{preview3D}->load_print;
+        }
+    });
+    
     # toolbar for object manipulation
     if (!&Wx::wxMSW) {
         Wx::ToolTip::Enable(1);
@@ -250,7 +262,8 @@ sub new {
     }
     
     $_->SetDropTarget(Slic3r::GUI::Plater::DropTarget->new($self))
-        for grep defined($_), $self, $self->{canvas}, $self->{canvas3D}, $self->{list};
+        for grep defined($_),
+            $self, $self->{canvas}, $self->{canvas3D}, $self->{preview3D}, $self->{list};
     
     EVT_COMMAND($self, -1, $THUMBNAIL_DONE_EVENT, sub {
         my ($self, $event) = @_;
@@ -282,16 +295,23 @@ sub new {
         Slic3r::thread_cleanup();
     });
     
-    EVT_TIMER($self, CONFIG_TIMER_ID, sub {
-        my ($self, $event) = @_;
-        $self->async_apply_config;
-    });
+    if ($Slic3r::have_threads) {
+        my $timer_id = Wx::NewId();
+        $self->{apply_config_timer} = Wx::Timer->new($self, $timer_id);
+        EVT_TIMER($self, $timer_id, sub {
+            my ($self, $event) = @_;
+            $self->async_apply_config;
+        });
+    }
     
     $self->{canvas}->update_bed_size;
     if ($self->{canvas3D}) {
         $self->{canvas3D}->update_bed_size;
         $self->{canvas3D}->zoom_to_bed;
     }
+    if ($self->{preview3D}) {
+        $self->{preview3D}->set_bed_shape($self->{config}->bed_shape);
+    }
     $self->update;
     
     {
@@ -549,6 +569,7 @@ sub remove {
     
     # Prevent toolpaths preview from rendering while we modify the Print object
     $self->{toolpaths2D}->enabled(0) if $self->{toolpaths2D};
+    $self->{preview3D}->enabled(0) if $self->{preview3D};
     
     # if no object index is supplied, remove the selected one
     if (!defined $obj_idx) {
@@ -573,6 +594,7 @@ sub reset {
     
     # Prevent toolpaths preview from rendering while we modify the Print object
     $self->{toolpaths2D}->enabled(0) if $self->{toolpaths2D};
+    $self->{preview3D}->enabled(0) if $self->{preview3D};
     
     @{$self->{objects}} = ();
     $self->{model}->clear_objects;
@@ -585,17 +607,20 @@ sub reset {
 }
 
 sub increase {
-    my $self = shift;
+    my ($self, $copies) = @_;
     
+    $copies //= 1;
     my ($obj_idx, $object) = $self->selected_object;
     my $model_object = $self->{model}->objects->[$obj_idx];
-    my $last_instance = $model_object->instances->[-1];
-    my $i = $model_object->add_instance(
-        offset          => Slic3r::Pointf->new(map 10+$_, @{$last_instance->offset}),
-        scaling_factor  => $last_instance->scaling_factor,
-        rotation        => $last_instance->rotation,
-    );
-    $self->{print}->objects->[$obj_idx]->add_copy($i->offset);
+    my $instance = $model_object->instances->[-1];
+    for my $i (1..$copies) {
+        $instance = $model_object->add_instance(
+            offset          => Slic3r::Pointf->new(map 10+$_, @{$instance->offset}),
+            scaling_factor  => $instance->scaling_factor,
+            rotation        => $instance->rotation,
+        );
+        $self->{print}->objects->[$obj_idx]->add_copy($instance->offset);
+    }
     $self->{list}->SetItem($obj_idx, 1, $model_object->instances_count);
     
     # only autoarrange if user has autocentering enabled
@@ -609,15 +634,18 @@ sub increase {
 }
 
 sub decrease {
-    my $self = shift;
+    my ($self, $copies) = @_;
     
+    $copies //= 1;
     $self->stop_background_process;
     
     my ($obj_idx, $object) = $self->selected_object;
     my $model_object = $self->{model}->objects->[$obj_idx];
-    if ($model_object->instances_count >= 2) {
-        $model_object->delete_last_instance;
-        $self->{print}->objects->[$obj_idx]->delete_last_copy;
+    if ($model_object->instances_count > $copies) {
+        for my $i (1..$copies) {
+            $model_object->delete_last_instance;
+            $self->{print}->objects->[$obj_idx]->delete_last_copy;
+        }
         $self->{list}->SetItem($obj_idx, 1, $model_object->instances_count);
     } else {
         $self->remove;
@@ -631,6 +659,28 @@ sub decrease {
     $self->schedule_background_process;
 }
 
+sub set_number_of_copies {
+    my ($self) = @_;
+    
+    $self->pause_background_process;
+    
+    # get current number of copies
+    my ($obj_idx, $object) = $self->selected_object;
+    my $model_object = $self->{model}->objects->[$obj_idx];
+    
+    # prompt user
+    my $copies = Wx::GetNumberFromUser("", "Enter the number of copies of the selected object:", "Copies", $model_object->instances_count, 0, 1000, $self);
+    my $diff = $copies - $model_object->instances_count;
+    if ($diff == 0) {
+        # no variation
+        $self->resume_background_process;
+    } elsif ($diff > 0) {
+        $self->increase($diff);
+    } elsif ($diff < 0) {
+        $self->decrease(-$diff);
+    }
+}
+
 sub rotate {
     my $self = shift;
     my ($angle, $axis) = @_;
@@ -667,6 +717,9 @@ sub rotate {
             $_->set_rotation(0) for @{ $model_object->instances };
         }
         $model_object->rotate(deg2rad($angle), $axis);
+        
+        # realign object to Z = 0
+        $model_object->center_around_origin;
         $self->make_thumbnail($obj_idx);
     }
     
@@ -696,6 +749,9 @@ sub flip {
     
     $model_object->flip($axis);
     $model_object->update_bounding_box;
+    
+    # realign object to Z = 0
+    $model_object->center_around_origin;
     $self->make_thumbnail($obj_idx);
         
     # update print and start background processing
@@ -733,6 +789,7 @@ sub changescale {
         my $versor = [1,1,1];
         $versor->[$axis] = $scale/100;
         $model_object->scale_xyz(Slic3r::Pointf3->new(@$versor));
+        # object was already aligned to Z = 0, so no need to realign it
         $self->make_thumbnail($obj_idx);
     } else {
         # max scale factor should be above 2540 to allow importing files exported in inches
@@ -825,13 +882,16 @@ sub schedule_background_process {
     
     if (defined $self->{apply_config_timer}) {
         $self->{apply_config_timer}->Start(PROCESS_DELAY, 1);  # 1 = one shot
-        $self->{toolpaths2D}->reload_print;
     }
 }
 
 sub async_apply_config {
     my ($self) = @_;
     
+    # reset preview canvases
+    $self->{toolpaths2D}->reload_print if $self->{toolpaths2D};
+    $self->{preview3D}->reload_print if $self->{preview3D};
+    
     # pause process thread before applying new config
     # since we don't want to touch data that is being used by the threads
     $self->pause_background_process;
@@ -904,7 +964,8 @@ sub stop_background_process {
     $self->statusbar->SetCancelCallback(undef);
     $self->statusbar->StopBusy;
     $self->statusbar->SetStatusText("");
-    $self->{toolpaths2D}->reload_print;
+    $self->{toolpaths2D}->reload_print if $self->{toolpaths2D};
+    $self->{preview3D}->reload_print if $self->{preview3D};
     
     if ($self->{process_thread}) {
         Slic3r::debugf "Killing background process.\n";
@@ -1028,7 +1089,8 @@ sub on_process_completed {
     $self->{process_thread} = undef;
     
     return if $error;
-    $self->{toolpaths2D}->reload_print;
+    $self->{toolpaths2D}->reload_print if $self->{toolpaths2D};
+    $self->{preview3D}->reload_print if $self->{preview3D};
     
     # if we have an export filename, start a new thread for exporting G-code
     if ($self->{export_gcode_output_file}) {
@@ -1299,6 +1361,8 @@ sub on_config_change {
         if ($opt_key eq 'bed_shape') {
             $self->{canvas}->update_bed_size;
             $self->{canvas3D}->update_bed_size if $self->{canvas3D};
+            $self->{preview3D}->set_bed_shape($self->{config}->bed_shape)
+                if $self->{preview3D};
             $self->update;
         } elsif ($opt_key eq 'serial_port') {
             if ($config->get('serial_port')) {
@@ -1346,7 +1410,7 @@ sub list_item_activated {
     my ($self, $event, $obj_idx) = @_;
     
     $obj_idx //= $event->GetIndex;
-	$self->object_cut_dialog($obj_idx);
+	$self->object_settings_dialog($obj_idx);
 }
 
 sub object_cut_dialog {
@@ -1518,6 +1582,7 @@ sub refresh_canvases {
     
     $self->{canvas}->Refresh;
     $self->{canvas3D}->update if $self->{canvas3D};
+    $self->{preview3D}->reload_print if $self->{preview3D};
 }
 
 sub validate_config {
@@ -1549,6 +1614,9 @@ sub object_menu {
     $frame->_append_menu_item($menu, "Decrease copies\tCtrl+-", 'Remove one copy of the selected object', sub {
         $self->decrease;
     });
+    $frame->_append_menu_item($menu, "Set number of copies…", 'Change the number of copies of the selected object', sub {
+        $self->set_number_of_copies;
+    });
     $menu->AppendSeparator();
     $frame->_append_menu_item($menu, "Rotate 45° clockwise", 'Rotate the selected object by 45° clockwise', sub {
         $self->rotate(-45);
diff --git a/lib/Slic3r/GUI/Plater/2D.pm b/lib/Slic3r/GUI/Plater/2D.pm
index a43f0a061..bf0dcbfba 100644
--- a/lib/Slic3r/GUI/Plater/2D.pm
+++ b/lib/Slic3r/GUI/Plater/2D.pm
@@ -27,7 +27,7 @@ sub new {
     $self->{on_select_object}   = sub {};
     $self->{on_double_click}    = sub {};
     $self->{on_right_click}     = sub {};
-    $self->{on_instance_moved}  = sub {};
+    $self->{on_instances_moved} = sub {};
     
     $self->{objects_brush}      = Wx::Brush->new(Wx::Colour->new(210,210,210), wxSOLID);
     $self->{selected_brush}     = Wx::Brush->new(Wx::Colour->new(255,128,128), wxSOLID);
@@ -63,9 +63,9 @@ sub on_right_click {
     $self->{on_right_click} = $cb;
 }
 
-sub on_instance_moved {
+sub on_instances_moved {
     my ($self, $cb) = @_;
-    $self->{on_instance_moved} = $cb;
+    $self->{on_instances_moved} = $cb;
 }
 
 sub repaint {
@@ -211,7 +211,7 @@ sub mouse_event {
         }
         $self->Refresh;
     } elsif ($event->LeftUp) {
-        $self->{on_instance_moved}->(@{ $self->{drag_object} })
+        $self->{on_instances_moved}->()
             if $self->{drag_object};
         $self->{drag_start_pos} = undef;
         $self->{drag_object} = undef;
diff --git a/lib/Slic3r/GUI/Plater/3D.pm b/lib/Slic3r/GUI/Plater/3D.pm
index a2b72033b..5928625ef 100644
--- a/lib/Slic3r/GUI/Plater/3D.pm
+++ b/lib/Slic3r/GUI/Plater/3D.pm
@@ -8,7 +8,7 @@ use Slic3r::Geometry qw();
 use Slic3r::Geometry::Clipper qw();
 use Wx qw(:misc :pen :brush :sizer :font :cursor wxTAB_TRAVERSAL);
 use Wx::Event qw();
-use base 'Slic3r::GUI::PreviewCanvas';
+use base qw(Slic3r::GUI::3DScene Class::Accessor);
 
 sub new {
     my $class = shift;
@@ -17,45 +17,42 @@ sub new {
     my $self = $class->SUPER::new($parent);
     $self->enable_picking(1);
     $self->enable_moving(1);
+    $self->select_by('object');
+    $self->drag_by('instance');
     
     $self->{objects}            = $objects;
     $self->{model}              = $model;
     $self->{config}             = $config;
     $self->{on_select_object}   = sub {};
-    $self->{on_instance_moved}  = sub {};
+    $self->{on_instances_moved} = sub {};
     
     $self->on_select(sub {
         my ($volume_idx) = @_;
         
         my $obj_idx = undef;
         if ($volume_idx != -1) {
-            $obj_idx = $self->{_volumes_inv}{$volume_idx};
-            $self->volumes->[$_]->selected(1) for @{$self->{_volumes}{$obj_idx}};
-            $self->Refresh;
+            $obj_idx = $self->object_idx($volume_idx);
         }
         $self->{on_select_object}->($obj_idx)
             if $self->{on_select_object};
     });
-    $self->on_hover(sub {
-        my ($volume_idx) = @_;
-        
-        my $obj_idx = $self->{_volumes_inv}{$volume_idx};
-        $self->volumes->[$_]->hover(1) for @{$self->{_volumes}{$obj_idx}};
-    });
     $self->on_move(sub {
-        my ($volume_idx) = @_;
+        my @volume_idxs = @_;
         
-        my $volume = $self->volumes->[$volume_idx];
-        my $obj_idx = $self->{_volumes_inv}{$volume_idx};
-        my $model_object = $self->{model}->get_object($obj_idx);
-        $model_object
-            ->instances->[$volume->instance_idx]
-            ->offset
-            ->translate($volume->origin->x, $volume->origin->y); #))
-        $model_object->invalidate_bounding_box;
+        foreach my $volume_idx (@volume_idxs) {
+            my $volume = $self->volumes->[$volume_idx];
+            my $obj_idx = $self->object_idx($volume_idx);
+            my $instance_idx = $self->instance_idx($volume_idx);
+            my $model_object = $self->{model}->get_object($obj_idx);
+            $model_object
+                ->instances->[$instance_idx]
+                ->offset
+                ->translate($volume->origin->x, $volume->origin->y); #))
+            $model_object->invalidate_bounding_box;
+        }
         
-        $self->{on_instance_moved}->($obj_idx, $volume->instance_idx)
-            if $self->{on_instance_moved};
+        $self->{on_instances_moved}->()
+            if $self->{on_instances_moved};
     });
     
     return $self;
@@ -76,27 +73,19 @@ sub set_on_right_click {
     $self->on_right_click($cb);
 }
 
-sub set_on_instance_moved {
+sub set_on_instances_moved {
     my ($self, $cb) = @_;
-    $self->{on_instance_moved} = $cb;
+    $self->{on_instances_moved} = $cb;
 }
 
 sub update {
     my ($self) = @_;
     
-    $self->{_volumes} = {};     # obj_idx => [ volume_idx, volume_idx ]
-    $self->{_volumes_inv} = {}; # volume_idx => obj_idx
     $self->reset_objects;
-    
     $self->update_bed_size;
     
     foreach my $obj_idx (0..$#{$self->{model}->objects}) {
-        my $model_object = $self->{model}->get_object($obj_idx);
-        my @volume_idxs = $self->load_object($model_object, 1);
-        
-        # store mapping between canvas volumes and model objects
-        $self->{_volumes}{$obj_idx} = [ @volume_idxs ];
-        $self->{_volumes_inv}{$_} = $obj_idx for @volume_idxs;
+        my @volume_idxs = $self->load_object($self->{model}, $obj_idx);
         
         if ($self->{objects}[$obj_idx]->selected) {
             $self->select_volume($_) for @volume_idxs;
diff --git a/lib/Slic3r/GUI/Plater/3DPreview.pm b/lib/Slic3r/GUI/Plater/3DPreview.pm
new file mode 100644
index 000000000..be9b5f572
--- /dev/null
+++ b/lib/Slic3r/GUI/Plater/3DPreview.pm
@@ -0,0 +1,144 @@
+package Slic3r::GUI::Plater::3DPreview;
+use strict;
+use warnings;
+use utf8;
+
+use Slic3r::Print::State ':steps';
+use Wx qw(:misc :sizer :slider :statictext wxWHITE);
+use Wx::Event qw(EVT_SLIDER EVT_KEY_DOWN);
+use base qw(Wx::Panel Class::Accessor);
+
+__PACKAGE__->mk_accessors(qw(print enabled _loaded canvas slider));
+
+sub new {
+    my $class = shift;
+    my ($parent, $print) = @_;
+    
+    my $self = $class->SUPER::new($parent, -1, wxDefaultPosition);
+    
+    # init GUI elements
+    my $canvas = Slic3r::GUI::3DScene->new($self);
+    $self->canvas($canvas);
+    my $slider = Wx::Slider->new(
+        $self, -1,
+        0,                              # default
+        0,                              # min
+        # we set max to a bogus non-zero value because the MSW implementation of wxSlider
+        # will skip drawing the slider if max <= min:
+        1,                              # max
+        wxDefaultPosition,
+        wxDefaultSize,
+        wxVERTICAL | wxSL_INVERSE,
+    );
+    $self->slider($slider);
+    
+    my $z_label = $self->{z_label} = Wx::StaticText->new($self, -1, "", wxDefaultPosition,
+        [40,-1], wxALIGN_CENTRE_HORIZONTAL);
+    $z_label->SetFont($Slic3r::GUI::small_font);
+    
+    my $vsizer = Wx::BoxSizer->new(wxVERTICAL);
+    $vsizer->Add($slider, 1, wxALL | wxEXPAND | wxALIGN_CENTER, 3);
+    $vsizer->Add($z_label, 0, wxALL | wxEXPAND | wxALIGN_CENTER, 3);
+    
+    my $sizer = Wx::BoxSizer->new(wxHORIZONTAL);
+    $sizer->Add($canvas, 1, wxALL | wxEXPAND, 0);
+    $sizer->Add($vsizer, 0, wxTOP | wxBOTTOM | wxEXPAND, 5);
+    
+    EVT_SLIDER($self, $slider, sub {
+        $self->set_z($self->{layers_z}[$slider->GetValue])
+            if $self->enabled;
+    });
+    EVT_KEY_DOWN($canvas, sub {
+        my ($s, $event) = @_;
+        
+        my $key = $event->GetKeyCode;
+        if ($key == 85 || $key == 315) {
+            $slider->SetValue($slider->GetValue + 1);
+            $self->set_z($self->{layers_z}[$slider->GetValue]);
+        } elsif ($key == 68 || $key == 317) {
+            $slider->SetValue($slider->GetValue - 1);
+            $self->set_z($self->{layers_z}[$slider->GetValue]);
+        }
+    });
+    
+    $self->SetSizer($sizer);
+    $self->SetMinSize($self->GetSize);
+    $sizer->SetSizeHints($self);
+    
+    # init canvas
+    $self->print($print);
+    $self->reload_print;
+    
+    return $self;
+}
+
+sub reload_print {
+    my ($self) = @_;
+    
+    $self->canvas->reset_objects;
+    $self->_loaded(0);
+    $self->load_print;
+}
+
+sub load_print {
+    my ($self) = @_;
+    
+    return if $self->_loaded;
+    
+    # we require that there's at least one object and the posSlice step
+    # is performed on all of them (this ensures that _shifted_copies was
+    # populated and we know the number of layers)
+    if (!$self->print->object_step_done(STEP_SLICE)) {
+        $self->enabled(0);
+        $self->slider->Hide;
+        $self->canvas->Refresh;  # clears canvas
+        return;
+    }
+    
+    {
+        my %z = ();  # z => 1
+        foreach my $object (@{$self->{print}->objects}) {
+            foreach my $layer (@{$object->layers}, @{$object->support_layers}) {
+                $z{$layer->print_z} = 1;
+            }
+        }
+        $self->enabled(1);
+        $self->{layers_z} = [ sort { $a <=> $b } keys %z ];
+        $self->slider->SetRange(0, scalar(@{$self->{layers_z}})-1);
+        if ((my $z_idx = $self->slider->GetValue) <= $#{$self->{layers_z}} && $self->slider->GetValue != 0) {
+            $self->set_z($self->{layers_z}[$z_idx]);
+        } else {
+            $self->slider->SetValue(scalar(@{$self->{layers_z}})-1);
+            $self->set_z($self->{layers_z}[-1]) if @{$self->{layers_z}};
+        }
+        $self->slider->Show;
+        $self->Layout;
+    }
+    
+    if ($self->IsShown) {
+        foreach my $object (@{$self->print->objects}) {
+            $self->canvas->load_print_object_toolpaths($object);
+            
+            #my @volume_ids = $self->canvas->load_object($object->model_object);
+            #$self->canvas->volumes->[$_]->color->[3] = 0.2 for @volume_ids;
+        }
+        $self->canvas->zoom_to_volumes;
+        $self->_loaded(1);
+    }
+}
+
+sub set_z {
+    my ($self, $z) = @_;
+    
+    return if !$self->enabled;
+    $self->{z_label}->SetLabel(sprintf '%.2f', $z);
+    $self->canvas->set_toolpaths_range(0, $z);
+    $self->canvas->Refresh if $self->IsShown;
+}
+
+sub set_bed_shape {
+    my ($self, $bed_shape) = @_;
+    $self->canvas->set_bed_shape($bed_shape);
+}
+
+1;
diff --git a/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm b/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm
index 24a580ab4..c0f942f12 100644
--- a/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm
+++ b/lib/Slic3r/GUI/Plater/ObjectCutDialog.pm
@@ -86,8 +86,9 @@ sub new {
     # right pane with preview canvas
     my $canvas;
     if ($Slic3r::GUI::have_OpenGL) {
-        $canvas = $self->{canvas} = Slic3r::GUI::PreviewCanvas->new($self);
-        $canvas->load_object($self->{model_object});
+        $canvas = $self->{canvas} = Slic3r::GUI::3DScene->new($self);
+        $canvas->enable_cutting(1);
+        $canvas->load_object($self->{model_object}, undef, [0]);
         $canvas->set_auto_bed_shape;
         $canvas->SetSize([500,500]);
         $canvas->SetMinSize($canvas->GetSize);
@@ -153,6 +154,7 @@ sub perform_cut {
     $self->{new_model} = $new_model;
     $self->{new_model_objects} = [];
     if ($self->{cut_options}{keep_upper} && $upper_object->volumes_count > 0) {
+        $upper_object->center_around_origin;  # align to Z = 0
         push @{$self->{new_model_objects}}, $upper_object;
     }
     if ($self->{cut_options}{keep_lower} && $lower_object->volumes_count > 0) {
diff --git a/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm b/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm
index 255a1685a..9956134ce 100644
--- a/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm
+++ b/lib/Slic3r/GUI/Plater/ObjectPartsPanel.pm
@@ -68,8 +68,18 @@ sub new {
     # right pane with preview canvas
     my $canvas;
     if ($Slic3r::GUI::have_OpenGL) {
-        $canvas = $self->{canvas} = Slic3r::GUI::PreviewCanvas->new($self);
-        $canvas->load_object($self->{model_object});
+        $canvas = $self->{canvas} = Slic3r::GUI::3DScene->new($self);
+        $canvas->enable_picking(1);
+        $canvas->select_by('volume');
+        
+        $canvas->on_select(sub {
+            my ($volume_idx) = @_;
+            
+            # convert scene volume to model object volume
+            $self->reload_tree($canvas->volume_idx($volume_idx));
+        });
+        
+        $canvas->load_object($self->{model_object}, undef, [0]);
         $canvas->set_auto_bed_shape;
         $canvas->SetSize([500,500]);
         $canvas->zoom_to_volumes;
@@ -101,20 +111,24 @@ sub new {
 }
 
 sub reload_tree {
-    my ($self) = @_;
+    my ($self, $selected_volume_idx) = @_;
     
+    $selected_volume_idx //= -1;
     my $object  = $self->{model_object};
     my $tree    = $self->{tree};
     my $rootId  = $tree->GetRootItem;
     
     $tree->DeleteChildren($rootId);
     
-    my $itemId;
+    my $selectedId = $rootId;
     foreach my $volume_id (0..$#{$object->volumes}) {
         my $volume = $object->volumes->[$volume_id];
         
         my $icon = $volume->modifier ? ICON_MODIFIERMESH : ICON_SOLIDMESH;
-        $itemId = $tree->AppendItem($rootId, $volume->name || $volume_id, $icon);
+        my $itemId = $tree->AppendItem($rootId, $volume->name || $volume_id, $icon);
+        if ($volume_id == $selected_volume_idx) {
+            $selectedId = $itemId;
+        }
         $tree->SetPlData($itemId, {
             type        => 'volume',
             volume_id   => $volume_id,
@@ -122,10 +136,9 @@ sub reload_tree {
     }
     $tree->ExpandAll;
     
-    # select last appended part
     # This will trigger the selection_changed() event
     Slic3r::GUI->CallAfter(sub {
-        $self->{tree}->SelectItem($itemId);
+        $self->{tree}->SelectItem($selectedId);
     });
 }
 
@@ -144,7 +157,7 @@ sub selection_changed {
     
     # deselect all meshes
     if ($self->{canvas}) {
-        $_->{selected} = 0 for @{$self->{canvas}->volumes};
+        $_->selected(0) for @{$self->{canvas}->volumes};
     }
     
     # disable things as if nothing is selected
@@ -169,10 +182,7 @@ sub selection_changed {
             # get default values
             @opt_keys = @{Slic3r::Config::PrintRegion->new->get_keys};
         } elsif ($itemData->{type} eq 'object') {
-            # select all object volumes in 3D preview
-            if ($self->{canvas}) {
-                $_->{selected} = 1 for @{$self->{canvas}->volumes};
-            }
+            # select nothing in 3D preview
             
             # attach object config to settings panel
             $self->{staticbox}->SetLabel('Object Settings');
diff --git a/lib/Slic3r/GUI/Plater/ObjectPreviewDialog.pm b/lib/Slic3r/GUI/Plater/ObjectPreviewDialog.pm
deleted file mode 100644
index 9d650fc83..000000000
--- a/lib/Slic3r/GUI/Plater/ObjectPreviewDialog.pm
+++ /dev/null
@@ -1,35 +0,0 @@
-package Slic3r::GUI::Plater::ObjectPreviewDialog;
-use strict;
-use warnings;
-use utf8;
-
-use Wx qw(:dialog :id :misc :sizer :systemsettings :notebook wxTAB_TRAVERSAL);
-use Wx::Event qw(EVT_CLOSE);
-use base 'Wx::Dialog';
-
-sub new {
-    my $class = shift;
-    my ($parent, %params) = @_;
-    my $self = $class->SUPER::new($parent, -1, $params{object}->name, wxDefaultPosition, [500,500], wxDEFAULT_DIALOG_STYLE | wxRESIZE_BORDER);
-    $self->{model_object} = $params{model_object};
-    
-    my $canvas = Slic3r::GUI::PreviewCanvas->new($self);
-    $canvas->load_object($self->{model_object});
-    $canvas->set_bounding_box($self->{model_object}->bounding_box);
-    $canvas->set_auto_bed_shape;
-    
-    my $sizer = Wx::BoxSizer->new(wxVERTICAL);
-    $sizer->Add($canvas, 1, wxEXPAND, 0);
-    $self->SetSizer($sizer);
-    $self->SetMinSize($self->GetSize);
-    
-    # needed to actually free memory
-    EVT_CLOSE($self, sub {
-        $self->EndModal(wxID_OK);
-        $self->Destroy;
-    });
-    
-    return $self;
-}
-
-1;
diff --git a/lib/Slic3r/GUI/SimpleTab.pm b/lib/Slic3r/GUI/SimpleTab.pm
index 93f4b3830..4c693fd44 100644
--- a/lib/Slic3r/GUI/SimpleTab.pm
+++ b/lib/Slic3r/GUI/SimpleTab.pm
@@ -22,6 +22,7 @@ sub new {
     $self->{vsizer} = Wx::BoxSizer->new(wxVERTICAL);
     $self->SetSizer($self->{vsizer});
     $self->build;
+    $self->_update;
     
     {
         my $label = Wx::StaticText->new($self, -1, "Want more options? Switch to the Expert Mode.", wxDefaultPosition, wxDefaultSize);
@@ -71,12 +72,14 @@ sub load_config {
         $self->{config}->set($opt_key, $config->get($opt_key));
     }
     $_->reload_config for @{$self->{optgroups}};
+    $self->_update;
 }
 
 sub load_presets {}
 
 sub is_dirty { 0 }
 sub config { $_[0]->{config}->clone }
+sub _update {}
 
 sub on_value_change {
     my ($self, $cb) = @_;
@@ -88,7 +91,19 @@ sub on_presets_changed {}
 # propagate event to the parent
 sub _on_value_change {
     my $self = shift;
+    
     $self->{on_value_change}->(@_) if $self->{on_value_change};
+    $self->_update;
+}
+
+sub get_field {
+    my ($self, $opt_key, $opt_index) = @_;
+    
+    foreach my $optgroup (@{ $self->{optgroups} }) {
+        my $field = $optgroup->get_fieldc($opt_key, $opt_index);
+        return $field if defined $field;
+    }
+    return undef;
 }
 
 package Slic3r::GUI::SimpleTab::Print;
@@ -104,10 +119,12 @@ sub build {
     
     $self->init_config_options(qw(
         layer_height perimeters top_solid_layers bottom_solid_layers 
-        fill_density fill_pattern support_material support_material_spacing raft_layers
+        fill_density fill_pattern external_fill_pattern
+        support_material support_material_spacing raft_layers
+        support_material_contact_distance dont_support_bridges
         perimeter_speed infill_speed travel_speed
         brim_width
-        complete_objects extruder_clearance_radius extruder_clearance_height
+        xy_size_compensation
     ));
     
     {
@@ -127,12 +144,15 @@ sub build {
         my $optgroup = $self->new_optgroup('Infill');
         $optgroup->append_single_option_line('fill_density');
         $optgroup->append_single_option_line('fill_pattern');
+        $optgroup->append_single_option_line('external_fill_pattern');
     }
     
     {
         my $optgroup = $self->new_optgroup('Support material');
         $optgroup->append_single_option_line('support_material');
         $optgroup->append_single_option_line('support_material_spacing');
+        $optgroup->append_single_option_line('support_material_contact_distance');
+        $optgroup->append_single_option_line('dont_support_bridges');
         $optgroup->append_single_option_line('raft_layers');
     }
     
@@ -149,18 +169,35 @@ sub build {
     }
     
     {
-        my $optgroup = $self->new_optgroup('Sequential printing');
-        $optgroup->append_single_option_line('complete_objects');
-        
-        my $line = Slic3r::GUI::OptionsGroup::Line->new(
-            label => 'Extruder clearance (mm)',
-        );
-        $line->append_option($optgroup->get_option('extruder_clearance_radius'));
-        $line->append_option($optgroup->get_option('extruder_clearance_height'));
-        $optgroup->append_line($line);
+        my $optgroup = $self->new_optgroup('Other');
+        $optgroup->append_single_option_line('xy_size_compensation');
     }
 }
 
+sub _update {
+    my ($self) = @_;
+    
+    my $config = $self->{config};
+    
+    my $have_perimeters = $config->perimeters > 0;
+    $self->get_field($_)->toggle($have_perimeters)
+        for qw(perimeter_speed);
+    
+    my $have_infill = $config->fill_density > 0;
+    my $have_solid_infill = $config->top_solid_layers > 0 || $config->bottom_solid_layers > 0;
+    $self->get_field($_)->toggle($have_infill)
+        for qw(fill_pattern);
+    $self->get_field($_)->toggle($have_solid_infill)
+        for qw(external_fill_pattern);
+    $self->get_field($_)->toggle($have_infill || $have_solid_infill)
+        for qw(infill_speed);
+    
+    my $have_support_material = $config->support_material || $config->raft_layers > 0;
+    $self->get_field($_)->toggle($have_support_material)
+        for qw(support_material_spacing dont_support_bridges
+            support_material_contact_distance);
+}
+
 package Slic3r::GUI::SimpleTab::Filament;
 use base 'Slic3r::GUI::SimpleTab';
 
@@ -206,6 +243,8 @@ sub build {
 
 package Slic3r::GUI::SimpleTab::Printer;
 use base 'Slic3r::GUI::SimpleTab';
+use Wx qw(:sizer :button :bitmap :misc :id);
+use Wx::Event qw(EVT_BUTTON);
 
 sub name { 'printer' }
 sub title { 'Printer Settings' }
@@ -214,17 +253,46 @@ sub build {
     my $self = shift;
     
     $self->init_config_options(qw(
+        bed_shape
         z_offset
         gcode_flavor
         nozzle_diameter
-        retract_length retract_lift
+        retract_length retract_lift wipe
         start_gcode
         end_gcode
     ));
     
     {
+        my $bed_shape_widget = sub {
+            my ($parent) = @_;
+        
+            my $btn = Wx::Button->new($parent, -1, "Set…", wxDefaultPosition, wxDefaultSize, wxBU_LEFT);
+            $btn->SetFont($Slic3r::GUI::small_font);
+            if ($Slic3r::GUI::have_button_icons) {
+                $btn->SetBitmap(Wx::Bitmap->new("$Slic3r::var/cog.png", wxBITMAP_TYPE_PNG));
+            }
+        
+            my $sizer = Wx::BoxSizer->new(wxHORIZONTAL);
+            $sizer->Add($btn);
+        
+            EVT_BUTTON($self, $btn, sub {
+                my $dlg = Slic3r::GUI::BedShapeDialog->new($self, $self->{config}->bed_shape);
+                if ($dlg->ShowModal == wxID_OK) {
+                    my $value = $dlg->GetValue;
+                    $self->{config}->set('bed_shape', $value);
+                    $self->_on_value_change('bed_shape', $value);
+                }
+            });
+        
+            return $sizer;
+        };
+    
         my $optgroup = $self->new_optgroup('Size and coordinates');
-        # TODO: add bed_shape
+        my $line = Slic3r::GUI::OptionsGroup::Line->new(
+            label       => 'Bed shape',
+            widget      => $bed_shape_widget,
+        );
+        $optgroup->append_line($line);
         $optgroup->append_single_option_line('z_offset');
     }
     
@@ -242,6 +310,7 @@ sub build {
         my $optgroup = $self->new_optgroup('Retraction');
         $optgroup->append_single_option_line('retract_length', 0);
         $optgroup->append_single_option_line('retract_lift', 0);
+        $optgroup->append_single_option_line('wipe', 0);
     }
     
     {
@@ -265,4 +334,14 @@ sub build {
     }
 }
 
+sub _update {
+    my ($self) = @_;
+    
+    my $config = $self->{config};
+    
+    my $have_retraction = $config->retract_length->[0] > 0;
+    $self->get_field($_, 0)->toggle($have_retraction)
+        for qw(retract_lift wipe);
+}
+
 1;
diff --git a/lib/Slic3r/GUI/Tab.pm b/lib/Slic3r/GUI/Tab.pm
index a30613197..67c5f57e1 100644
--- a/lib/Slic3r/GUI/Tab.pm
+++ b/lib/Slic3r/GUI/Tab.pm
@@ -292,16 +292,24 @@ sub reload_config {
 }
 
 sub update_tree {
-    my $self = shift;
-    my ($select) = @_;
+    my ($self) = @_;
     
-    $select //= 0; #/
+    # get label of the currently selected item
+    my $selected = $self->{treectrl}->GetItemText($self->{treectrl}->GetSelection);
     
     my $rootItem = $self->{treectrl}->GetRootItem;
     $self->{treectrl}->DeleteChildren($rootItem);
+    my $have_selection = 0;
     foreach my $page (@{$self->{pages}}) {
         my $itemId = $self->{treectrl}->AppendItem($rootItem, $page->{title}, $page->{iconID});
-        $self->{treectrl}->SelectItem($itemId) if $self->{treectrl}->GetChildrenCount($rootItem) == $select + 1;
+        if ($page->{title} eq $selected) {
+            $self->{treectrl}->SelectItem($itemId);
+            $have_selection = 1;
+        }
+    }
+    
+    if (!$have_selection) {
+        $self->{treectrl}->SelectItem($self->{treectrl}->GetFirstChild($rootItem));
     }
 }
 
@@ -391,6 +399,7 @@ sub load_config {
         $self->update_dirty;
     }
     $self->reload_config;
+    $self->_update;
 }
 
 sub get_preset_config {
@@ -453,7 +462,7 @@ sub build {
         raft_layers
         support_material_pattern support_material_spacing support_material_angle
         support_material_interface_layers support_material_interface_spacing
-        dont_support_bridges
+        support_material_contact_distance dont_support_bridges
         notes
         complete_objects extruder_clearance_radius extruder_clearance_height
         gcode_comments output_filename_format
@@ -465,7 +474,7 @@ sub build {
         extrusion_width first_layer_extrusion_width perimeter_extrusion_width 
         external_perimeter_extrusion_width infill_extrusion_width solid_infill_extrusion_width 
         top_infill_extrusion_width support_material_extrusion_width
-        bridge_flow_ratio
+        infill_overlap bridge_flow_ratio
         xy_size_compensation threads resolution
     ));
     
@@ -556,6 +565,7 @@ sub build {
         }
         {
             my $optgroup = $page->new_optgroup('Options for support material and raft');
+            $optgroup->append_single_option_line('support_material_contact_distance');
             $optgroup->append_single_option_line('support_material_pattern');
             $optgroup->append_single_option_line('support_material_spacing');
             $optgroup->append_single_option_line('support_material_angle');
@@ -634,6 +644,10 @@ sub build {
             $optgroup->append_single_option_line('top_infill_extrusion_width');
             $optgroup->append_single_option_line('support_material_extrusion_width');
         }
+        {
+            my $optgroup = $page->new_optgroup('Overlap');
+            $optgroup->append_single_option_line('infill_overlap');
+        }
         {
             my $optgroup = $page->new_optgroup('Flow');
             $optgroup->append_single_option_line('bridge_flow_ratio');
@@ -702,13 +716,20 @@ sub _update {
     my $config = $self->{config};
     
     if ($config->spiral_vase && !($config->perimeters == 1 && $config->top_solid_layers == 0 && $config->fill_density == 0)) {
-        my $dialog = Wx::MessageDialog->new($self, "The Spiral Vase mode requires one perimeter, no top solid layers and 0% fill density. Shall I adjust those settings in order to enable Spiral Vase?",
+        my $dialog = Wx::MessageDialog->new($self,
+            "The Spiral Vase mode requires:\n"
+            . "- one perimeter\n"
+            . "- no top solid layers\n"
+            . "- 0% fill density\n"
+            . "- no support material\n"
+            . "\nShall I adjust those settings in order to enable Spiral Vase?",
             'Spiral Vase', wxICON_WARNING | wxYES | wxNO);
         if ($dialog->ShowModal() == wxID_YES) {
             my $new_conf = Slic3r::Config->new;
             $new_conf->set("perimeters", 1);
             $new_conf->set("top_solid_layers", 0);
             $new_conf->set("fill_density", 0);
+            $new_conf->set("support_material", 0);
             $self->load_config($new_conf);
         } else {
             my $new_conf = Slic3r::Config->new;
@@ -759,7 +780,7 @@ sub _update {
         for qw(support_material_threshold support_material_enforce_layers
             support_material_pattern support_material_spacing support_material_angle
             support_material_interface_layers dont_support_bridges
-            support_material_extrusion_width);
+            support_material_extrusion_width support_material_contact_distance);
     $self->get_field($_)->toggle($have_support_material && $have_support_interface)
         for qw(support_material_interface_spacing support_material_interface_extruder
             support_material_interface_speed);
@@ -929,7 +950,7 @@ sub build {
         octoprint_host octoprint_apikey
         use_firmware_retraction pressure_advance vibration_limit
         use_volumetric_e
-        start_gcode end_gcode layer_gcode toolchange_gcode
+        start_gcode end_gcode before_layer_gcode layer_gcode toolchange_gcode
         nozzle_diameter extruder_offset
         retract_length retract_lift retract_speed retract_restart_extra retract_before_travel retract_layer_change wipe
         retract_length_toolchange retract_restart_extra_toolchange
@@ -1037,7 +1058,7 @@ sub build {
                 EVT_BUTTON($self, $btn, sub {
                     my $dlg = Slic3r::GUI::BonjourBrowser->new($self);
                     if ($dlg->ShowModal == wxID_OK) {
-                        my $value = $dlg->GetValue;
+                        my $value = $dlg->GetValue . ":" . $dlg->GetPort;
                         $self->{config}->set('octoprint_host', $value);
                         $self->update_dirty;
                         $self->_on_value_change('octoprint_host', $value);
@@ -1060,7 +1081,7 @@ sub build {
                     my $ua = LWP::UserAgent->new;
                     $ua->timeout(10);
     
-                    my $res = $ua->post(
+                    my $res = $ua->get(
                         "http://" . $self->{config}->octoprint_host . "/api/version",
                         'X-Api-Key' => $self->{config}->octoprint_apikey,
                     );
@@ -1115,7 +1136,16 @@ sub build {
             $optgroup->append_single_option_line($option);
         }
         {
-            my $optgroup = $page->new_optgroup('Layer change G-code',
+            my $optgroup = $page->new_optgroup('Before layer change G-code',
+                label_width => 0,
+            );
+            my $option = $optgroup->get_option('before_layer_gcode');
+            $option->full_width(1);
+            $option->height(150);
+            $optgroup->append_single_option_line($option);
+        }
+        {
+            my $optgroup = $page->new_optgroup('After layer change G-code',
                 label_width => 0,
             );
             my $option = $optgroup->get_option('layer_gcode');
@@ -1203,6 +1233,7 @@ sub _build_extruder_pages {
     
     # remove extra pages
     if ($self->{extruders_count} <= $#{$self->{extruder_pages}}) {
+        $_->Destroy for @{$self->{extruder_pages}}[$self->{extruders_count}..$#{$self->{extruder_pages}}];
         splice @{$self->{extruder_pages}}, $self->{extruders_count};
     }
     
@@ -1219,7 +1250,7 @@ sub _build_extruder_pages {
         (grep $_->{title} !~ /^Extruder \d+/, @{$self->{pages}}),
         @{$self->{extruder_pages}}[ 0 .. $self->{extruders_count}-1 ],
     );
-    $self->update_tree(0);
+    $self->update_tree;
 }
 
 sub _update {
@@ -1420,8 +1451,8 @@ sub config {
         return Slic3r::Config->new_from_defaults(@$keys);
     } else {
         if (!-e $self->file) {
-            Slic3r::GUI::show_error($self, "The selected preset does not exist anymore (" . $self->file . ").");
-            return;
+            Slic3r::GUI::show_error(undef, "The selected preset does not exist anymore (" . $self->file . ").");
+            return undef;
         }
         
         # apply preset values on top of defaults
diff --git a/lib/Slic3r/Layer/PerimeterGenerator.pm b/lib/Slic3r/Layer/PerimeterGenerator.pm
index 90893d535..6dcbe5733 100644
--- a/lib/Slic3r/Layer/PerimeterGenerator.pm
+++ b/lib/Slic3r/Layer/PerimeterGenerator.pm
@@ -5,7 +5,7 @@ use Slic3r::ExtrusionLoop ':roles';
 use Slic3r::ExtrusionPath ':roles';
 use Slic3r::Geometry qw(scale unscale chained_path);
 use Slic3r::Geometry::Clipper qw(union_ex diff diff_ex intersection_ex offset offset2
-    offset_ex offset2_ex union_pt intersection_ppl diff_ppl);
+    offset_ex offset2_ex intersection_ppl diff_ppl);
 use Slic3r::Surface ':types';
 
 has 'slices'                => (is => 'ro', required => 1);  # SurfaceCollection
@@ -17,6 +17,7 @@ has 'ext_perimeter_flow'    => (is => 'ro', required => 1);
 has 'overhang_flow'         => (is => 'ro', required => 1);
 has 'solid_infill_flow'     => (is => 'ro', required => 1);
 has 'config'                => (is => 'ro', default => sub { Slic3r::Config::PrintRegion->new });
+has 'object_config'         => (is => 'ro', default => sub { Slic3r::Config::PrintObject->new });
 has 'print_config'          => (is => 'ro', default => sub { Slic3r::Config::Print->new });
 has '_lower_slices_p'       => (is => 'rw', default => sub { [] });
 has '_holes_pt'             => (is => 'rw');
@@ -90,20 +91,23 @@ sub process {
     # we need to process each island separately because we might have different
     # extra perimeters for each one
     foreach my $surface (@{$self->slices}) {
-        my @contours    = ();    # array of Polygons with ccw orientation
-        my @holes       = ();    # array of Polygons with cw orientation
-        my @thin_walls  = ();    # array of ExPolygons
-        
         # detect how many perimeters must be generated for this island
         my $loop_number = $self->config->perimeters + ($surface->extra_perimeters || 0);
+        $loop_number--;  # 0-indexed loops
+        
+        my @gaps = ();   # ExPolygons
+        
+        my @last = @{$surface->expolygon->simplify_p(&Slic3r::SCALED_RESOLUTION)};
+        if ($loop_number >= 0) {  # no loops = -1
+        
+            my @contours    = ();   # depth => [ Polygon, Polygon ... ]
+            my @holes       = ();   # depth => [ Polygon, Polygon ... ]
+            my @thin_walls  = ();   # Polylines
         
-        my @last = @{$surface->expolygon};
-        my @gaps = ();    # array of ExPolygons
-        if ($loop_number > 0) {
             # we loop one time more than needed in order to find gaps after the last perimeter was applied
-            for my $i (1 .. ($loop_number+1)) {  # outer loop is 1
+            for my $i (0..($loop_number+1)) {  # outer loop is 0
                 my @offsets = ();
-                if ($i == 1) {
+                if ($i == 0) {
                     # the minimum thickness of a single loop is:
                     # ext_width/2 + ext_spacing/2 + spacing/2 + width/2
                     if ($self->config->thin_walls) {
@@ -121,15 +125,35 @@ sub process {
                     
                     # look for thin walls
                     if ($self->config->thin_walls) {
-                        my $diff = diff_ex(
+                        my $diff = diff(
                             \@last,
                             offset(\@offsets, +0.5*$ext_pwidth),
                             1,  # medial axis requires non-overlapping geometry
                         );
-                        push @thin_walls, @$diff;
+                        
+                        # the following offset2 ensures almost nothing in @thin_walls is narrower than $min_width
+                        # (actually, something larger than that still may exist due to mitering or other causes)
+                        my $min_width = $pwidth / 4;
+                        @thin_walls = @{offset2_ex($diff, -$min_width/2, +$min_width/2)};
+        
+                        # the maximum thickness of our thin wall area is equal to the minimum thickness of a single loop
+                        @thin_walls = grep $_->length > $pwidth*2,
+                            map @{$_->medial_axis($pwidth + $pspacing, $min_width)}, @thin_walls;
+                        Slic3r::debugf "  %d thin walls detected\n", scalar(@thin_walls) if $Slic3r::debug;
+        
+                        if (0) {
+                            require "Slic3r/SVG.pm";
+                            Slic3r::SVG::output(
+                                "medial_axis.svg",
+                                no_arrows => 1,
+                                expolygons      => union_ex($diff),
+                                green_polylines => [ map $_->polygon->split_at_first_point, @{$self->perimeters} ],
+                                red_polylines   => $self->_thin_wall_polylines,
+                            );
+                        }
                     }
                 } else {
-                    my $distance = ($i == 2) ? $ext_pspacing : $pspacing;
+                    my $distance = ($i == 1) ? $ext_pspacing : $pspacing;
                     
                     if ($self->config->thin_walls) {
                         @offsets = @{offset2(
@@ -159,17 +183,93 @@ sub process {
             
                 last if !@offsets;
                 last if $i > $loop_number; # we were only looking for gaps this time
-            
-                # clone polygons because these ExPolygons will go out of scope very soon
+                
                 @last = @offsets;
+                
+                $contours[$i]   = [];
+                $holes[$i]      = [];
                 foreach my $polygon (@offsets) {
-                    if ($polygon->is_counter_clockwise) {
-                        push @contours, $polygon;
+                    my $loop = Slic3r::Layer::PerimeterGenerator::Loop->new(
+                        polygon     => $polygon,
+                        is_contour  => $polygon->is_counter_clockwise,
+                        depth       => $i,
+                    );
+                    if ($loop->is_contour) {
+                        push @{$contours[$i]}, $loop;
                     } else {
-                        push @holes, $polygon;
+                        push @{$holes[$i]}, $loop;
                     }
                 }
             }
+            
+            # nest loops: holes first
+            for my $d (0..$loop_number) {
+                # loop through all holes having depth $d
+                LOOP: for (my $i = 0; $i <= $#{$holes[$d]}; ++$i) {
+                    my $loop = $holes[$d][$i];
+                
+                    # find the hole loop that contains this one, if any
+                    for my $t (($d+1)..$loop_number) {
+                        for (my $j = 0; $j <= $#{$holes[$t]}; ++$j) {
+                            my $candidate_parent = $holes[$t][$j];
+                            if ($candidate_parent->polygon->contains_point($loop->polygon->first_point)) {
+                                $candidate_parent->add_child($loop);
+                                splice @{$holes[$d]}, $i, 1;
+                                --$i;
+                                next LOOP;
+                            }
+                        }
+                    }
+                
+                    # if no hole contains this hole, find the contour loop that contains it
+                    for my $t (reverse 0..$loop_number) {
+                        for (my $j = 0; $j <= $#{$contours[$t]}; ++$j) {
+                            my $candidate_parent = $contours[$t][$j];
+                            if ($candidate_parent->polygon->contains_point($loop->polygon->first_point)) {
+                                $candidate_parent->add_child($loop);
+                                splice @{$holes[$d]}, $i, 1;
+                                --$i;
+                                next LOOP;
+                            }
+                        }
+                    }
+                }
+            }
+        
+            # nest contour loops
+            for my $d (reverse 1..$loop_number) {
+                # loop through all contours having depth $d
+                LOOP: for (my $i = 0; $i <= $#{$contours[$d]}; ++$i) {
+                    my $loop = $contours[$d][$i];
+                
+                    # find the contour loop that contains it
+                    for my $t (reverse 0..($d-1)) {
+                        for (my $j = 0; $j <= $#{$contours[$t]}; ++$j) {
+                            my $candidate_parent = $contours[$t][$j];
+                            if ($candidate_parent->polygon->contains_point($loop->polygon->first_point)) {
+                                $candidate_parent->add_child($loop);
+                                splice @{$contours[$d]}, $i, 1;
+                                --$i;
+                                next LOOP;
+                            }
+                        }
+                    }
+                }
+            }
+        
+            # at this point, all loops should be in $contours[0]
+            my @entities = $self->_traverse_loops($contours[0], \@thin_walls);
+            
+            # if brim will be printed, reverse the order of perimeters so that
+            # we continue inwards after having finished the brim
+            # TODO: add test for perimeter order
+            @entities = reverse @entities
+                if $self->config->external_perimeters_first
+                    || ($self->layer_id == 0 && $self->print_config->brim_width > 0);
+        
+            # append perimeters for this slice as a collection
+            $self->loops->append(Slic3r::ExtrusionPath::Collection->new(@entities))
+                if @entities;
         }
         
         # fill gaps
@@ -216,88 +316,42 @@ sub process {
             for map Slic3r::Surface->new(expolygon => $_, surface_type => S_TYPE_INTERNAL),  # use a bogus surface type
                 @{offset2_ex(
                     [ map @{$_->simplify_p(&Slic3r::SCALED_RESOLUTION)}, @{union_ex(\@last)} ],
-                    -($pspacing/2 + $min_perimeter_infill_spacing/2),
+                    -($pspacing/2 - $self->config->get_abs_value_over('infill_overlap', $pwidth) + $min_perimeter_infill_spacing/2),
                     +$min_perimeter_infill_spacing/2,
                 )};
-    
-    
-        # process thin walls by collapsing slices to single passes
-        if (@thin_walls) {
-            # the following offset2 ensures almost nothing in @thin_walls is narrower than $min_width
-            # (actually, something larger than that still may exist due to mitering or other causes)
-            my $min_width = $pwidth / 4;
-            @thin_walls = @{offset2_ex([ map @$_, @thin_walls ], -$min_width/2, +$min_width/2)};
-        
-            # the maximum thickness of our thin wall area is equal to the minimum thickness of a single loop
-            $self->_thin_wall_polylines([ map @{$_->medial_axis($pwidth + $pspacing, $min_width)}, @thin_walls ]);
-            Slic3r::debugf "  %d thin walls detected\n", scalar(@{$self->_thin_wall_polylines}) if $Slic3r::debug;
-        
-            if (0) {
-                require "Slic3r/SVG.pm";
-                Slic3r::SVG::output(
-                    "medial_axis.svg",
-                    no_arrows => 1,
-                    expolygons      => \@thin_walls,
-                    green_polylines => [ map $_->polygon->split_at_first_point, @{$self->perimeters} ],
-                    red_polylines   => $self->_thin_wall_polylines,
-                );
-            }
-        }
-        
-        # find nesting hierarchies separately for contours and holes
-        my $contours_pt = union_pt(\@contours);
-        $self->_holes_pt(union_pt(\@holes));
-    
-        # order loops from inner to outer (in terms of object slices)
-        my @loops = $self->_traverse_pt($contours_pt, 0, 1);
-    
-        # if brim will be printed, reverse the order of perimeters so that
-        # we continue inwards after having finished the brim
-        # TODO: add test for perimeter order
-        @loops = reverse @loops
-            if $self->config->external_perimeters_first
-                || ($self->layer_id == 0 && $self->print_config->brim_width > 0);
-        
-        # append perimeters for this slice as a collection
-        $self->loops->append(Slic3r::ExtrusionPath::Collection->new(@loops));
     }
 }
 
-sub _traverse_pt {
-    my ($self, $polynodes, $depth, $is_contour) = @_;
+sub _traverse_loops {
+    my ($self, $loops, $thin_walls) = @_;
     
-    # convert all polynodes to ExtrusionLoop objects
-    my $collection = Slic3r::ExtrusionPath::Collection->new;  # temporary collection
-    my @children = ();
-    foreach my $polynode (@$polynodes) {
-        my $polygon = ($polynode->{outer} // $polynode->{hole})->clone;
+    # loops is an arrayref of ::Loop objects
+    # turn each one into an ExtrusionLoop object
+    my $coll = Slic3r::ExtrusionPath::Collection->new;
+    foreach my $loop (@$loops) {
+        my $is_external = $loop->is_external;
         
-        my $role        = EXTR_ROLE_PERIMETER;
-        my $loop_role   = EXTRL_ROLE_DEFAULT;
-        
-        my $root_level  = $depth == 0;
-        my $no_children = !@{ $polynode->{children} };
-        my $is_external = $is_contour ? $root_level : $no_children;
-        my $is_internal = $is_contour ? $no_children : $root_level;
-        if ($is_contour && $is_internal) {
-            # internal perimeters are root level in case of holes
-            # and items with no children in case of contours
+        my ($role, $loop_role);
+        if ($is_external) {
+            $role = EXTR_ROLE_EXTERNAL_PERIMETER;
+        } else {
+            $role = EXTR_ROLE_PERIMETER;
+        }
+        if ($loop->is_internal_contour) {
             # Note that we set loop role to ContourInternalPerimeter
             # also when loop is both internal and external (i.e.
             # there's only one contour loop).
-            $loop_role  = EXTRL_ROLE_CONTOUR_INTERNAL_PERIMETER;
-        }
-        if ($is_external) {
-            # external perimeters are root level in case of contours
-            # and items with no children in case of holes
-            $role       = EXTR_ROLE_EXTERNAL_PERIMETER;
+            $loop_role = EXTRL_ROLE_CONTOUR_INTERNAL_PERIMETER;
+        } else {
+            $loop_role = EXTR_ROLE_PERIMETER;
         }
         
         # detect overhanging/bridging perimeters
         my @paths = ();
-        if ($self->config->overhangs && $self->layer_id > 0) {
+        if ($self->config->overhangs && $self->layer_id > 0
+            && !($self->object_config->support_material && $self->object_config->support_material_contact_distance == 0)) {
             # get non-overhang paths by intersecting this loop with the grown lower slices
-            foreach my $polyline (@{ intersection_ppl([ $polygon ], $self->_lower_slices_p) }) {
+            foreach my $polyline (@{ intersection_ppl([ $loop->polygon ], $self->_lower_slices_p) }) {
                 push @paths, Slic3r::ExtrusionPath->new(
                     polyline        => $polyline,
                     role            => $role,
@@ -310,13 +364,13 @@ sub _traverse_pt {
             # get overhang paths by checking what parts of this loop fall 
             # outside the grown lower slices (thus where the distance between
             # the loop centerline and original lower slices is >= half nozzle diameter
-            foreach my $polyline (@{ diff_ppl([ $polygon ], $self->_lower_slices_p) }) {
+            foreach my $polyline (@{ diff_ppl([ $loop->polygon ], $self->_lower_slices_p) }) {
                 push @paths, Slic3r::ExtrusionPath->new(
                     polyline        => $polyline,
                     role            => EXTR_ROLE_OVERHANG_PERIMETER,
                     mm3_per_mm      => $self->_mm3_per_mm_overhang,
                     width           => $self->overhang_flow->width,
-                    height          => $self->layer_height,
+                    height          => $self->overhang_flow->height,
                 );
             }
             
@@ -328,37 +382,22 @@ sub _traverse_pt {
             @paths = map $_->clone, @{$collection->chained_path(0)};
         } else {
             push @paths, Slic3r::ExtrusionPath->new(
-                polyline        => $polygon->split_at_first_point,
+                polyline        => $loop->polygon->split_at_first_point,
                 role            => $role,
                 mm3_per_mm      => $self->_mm3_per_mm,
                 width           => $self->perimeter_flow->width,
                 height          => $self->layer_height,
             );
         }
-        my $loop = Slic3r::ExtrusionLoop->new_from_paths(@paths);
-        $loop->role($loop_role);
-        
-        # return ccw contours and cw holes
-        # GCode.pm will convert all of them to ccw, but it needs to know
-        # what the holes are in order to compute the correct inwards move
-        # We do this on the final Loop object because overhang clipping
-        # does not keep orientation.
-        if ($is_contour) {
-            $loop->make_counter_clockwise;
-        } else {
-            $loop->make_clockwise;
-        }
-        $collection->append($loop);
-        
-        # save the children
-        push @children, $polynode->{children};
+        my $eloop = Slic3r::ExtrusionLoop->new_from_paths(@paths);
+        $eloop->role($loop_role);
+        $coll->append($eloop);
     }
-
-    # if we're handling the top-level contours, add thin walls as candidates too
-    # in order to include them in the nearest-neighbor search
-    if ($is_contour && $depth == 0) {
-        foreach my $polyline (@{$self->_thin_wall_polylines}) {
-            $collection->append(Slic3r::ExtrusionPath->new(
+    
+    # append thin walls to the nearest-neighbor search (only for first iteration)
+    if (@$thin_walls) {
+        foreach my $polyline (@$thin_walls) {
+            $coll->append(Slic3r::ExtrusionPath->new(
                 polyline        => $polyline,
                 role            => EXTR_ROLE_EXTERNAL_PERIMETER,
                 mm3_per_mm      => $self->_mm3_per_mm,
@@ -366,51 +405,37 @@ sub _traverse_pt {
                 height          => $self->layer_height,
             ));
         }
+        
+        @$thin_walls = ();
     }
     
-    # use a nearest neighbor search to order these children
-    # TODO: supply second argument to chained_path() too?
-    # (We used to skip this chained_path() when $is_contour &&
-    # $depth == 0 because slices are ordered at G_code export 
-    # time, but multiple top-level perimeters might belong to
-    # the same slice actually, so that was a broken optimization.)
-    # We supply no_reverse = false because we want to permit reversal
-    # of thin walls, but we rely on the fact that loops will never
-    # be reversed anyway.
-    my $sorted_collection = $collection->chained_path_indices(0);
-    my @orig_indices = @{$sorted_collection->orig_indices};
+    # sort entities
+    my $sorted_coll = $coll->chained_path_indices(0);
+    my @indices = @{$sorted_coll->orig_indices};
     
-    my @loops = ();
-    foreach my $loop (@$sorted_collection) {
-        my $orig_index = shift @orig_indices;
-        
-        if ($loop->isa('Slic3r::ExtrusionPath')) {
-            push @loops, $loop->clone;
+    # traverse children
+    my @entities = ();
+    for my $i (0..$#indices) {
+        my $idx = $indices[$i];
+        if ($idx > $#$loops) {
+            # this is a thin wall
+            # let's get it from the sorted collection as it might have been reversed
+            push @entities, $sorted_coll->[$i]->clone;
         } else {
-            # if this is an external contour find all holes belonging to this contour(s)
-            # and prepend them
-            if ($is_contour && $depth == 0) {
-                # $loop is the outermost loop of an island
-                my @holes = ();
-                for (my $i = 0; $i <= $#{$self->_holes_pt}; $i++) {
-                    if ($loop->polygon->contains_point($self->_holes_pt->[$i]{outer}->first_point)) {
-                        push @holes, splice @{$self->_holes_pt}, $i, 1;  # remove from candidates to reduce complexity
-                        $i--;
-                    }
-                }
-                
-                # order holes efficiently
-                @holes = @holes[@{chained_path([ map {($_->{outer} // $_->{hole})->first_point} @holes ])}];
-                
-                push @loops, reverse map $self->_traverse_pt([$_], 0, 0), @holes;
+            my $loop = $loops->[$idx];
+            my $eloop = $coll->[$idx]->clone;
+        
+            my @children = $self->_traverse_loops($loop->children, $thin_walls);
+            if ($loop->is_contour) {
+                $eloop->make_counter_clockwise;
+                push @entities, @children, $eloop;
+            } else {
+                $eloop->make_clockwise;
+                push @entities, $eloop, @children;
             }
-            
-            # traverse children and prepend them to this loop
-            push @loops, $self->_traverse_pt($children[$orig_index], $depth+1, $is_contour);
-            push @loops, $loop->clone;
         }
     }
-    return @loops;
+    return @entities;
 }
 
 sub _fill_gaps {
@@ -459,4 +484,35 @@ sub _fill_gaps {
     return @entities;
 }
 
+
+package Slic3r::Layer::PerimeterGenerator::Loop;
+use Moo;
+
+has 'polygon'       => (is => 'ro', required => 1);
+has 'is_contour'    => (is => 'ro', required => 1);
+has 'depth'         => (is => 'ro', required => 1);
+has 'children'      => (is => 'ro', default => sub { [] });
+
+use List::Util qw(first);
+
+sub add_child {
+    my ($self, $child) = @_;
+    push @{$self->children}, $child;
+}
+
+sub is_external {
+    my ($self) = @_;
+    return $self->depth == 0;
+}
+
+sub is_internal_contour {
+    my ($self) = @_;
+    
+    if ($self->is_contour) {
+        # an internal contour is a contour containing no other contours
+        return !defined first { $_->is_contour } @{$self->children};
+    }
+    return 0;
+}
+
 1;
diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index 88f0db01f..f65e90129 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -34,6 +34,7 @@ sub make_perimeters {
     my $generator = Slic3r::Layer::PerimeterGenerator->new(
         # input:
         config              => $self->config,
+        object_config       => $self->layer->object->config,
         print_config        => $self->layer->print->config,
         layer_height        => $self->height,
         layer_id            => $self->layer->id,
@@ -52,30 +53,6 @@ sub make_perimeters {
     $generator->process;
 }
 
-sub prepare_fill_surfaces {
-    my $self = shift;
-    
-    # Note: in order to make the psPrepareInfill step idempotent, we should never
-    # alter fill_surfaces boundaries on which our idempotency relies since that's
-    # the only meaningful information returned by psPerimeters.
-    
-    # if no solid layers are requested, turn top/bottom surfaces to internal
-    if ($self->config->top_solid_layers == 0) {
-        $_->surface_type(S_TYPE_INTERNAL) for @{$self->fill_surfaces->filter_by_type(S_TYPE_TOP)};
-    }
-    if ($self->config->bottom_solid_layers == 0) {
-        $_->surface_type(S_TYPE_INTERNAL)
-            for @{$self->fill_surfaces->filter_by_type(S_TYPE_BOTTOM)}, @{$self->fill_surfaces->filter_by_type(S_TYPE_BOTTOMBRIDGE)};
-    }
-        
-    # turn too small internal regions into solid regions according to the user setting
-    if ($self->config->fill_density > 0) {
-        my $min_area = scale scale $self->config->solid_infill_below_area; # scaling an area requires two calls!
-        $_->surface_type(S_TYPE_INTERNALSOLID)
-            for grep { $_->area <= $min_area } @{$self->fill_surfaces->filter_by_type(S_TYPE_INTERNAL)};
-    }
-}
-
 sub process_external_surfaces {
     my ($self, $lower_layer) = @_;
     
diff --git a/lib/Slic3r/Model.pm b/lib/Slic3r/Model.pm
index d3bbae030..1a2f62afd 100644
--- a/lib/Slic3r/Model.pm
+++ b/lib/Slic3r/Model.pm
@@ -12,6 +12,9 @@ sub read_from_file {
               : $input_file =~ /\.amf(\.xml)?$/i    ? Slic3r::Format::AMF->read_file($input_file)
               : die "Input file must have .stl, .obj or .amf(.xml) extension\n";
     
+    die "The supplied file couldn't be read because it's empty.\n"
+        if $model->objects_count == 0;
+    
     $_->set_input_file($input_file) for @{$model->objects};
     return $model;
 }
@@ -272,6 +275,7 @@ sub rotate {
     } elsif ($axis == Z) {
         $_->mesh->rotate_z($angle) for @{$self->volumes};
     }
+    $self->set_origin_translation(Slic3r::Pointf3->new(0,0,0));
     $self->invalidate_bounding_box;
 }
 
@@ -285,6 +289,7 @@ sub flip {
     } elsif ($axis == Z) {
         $_->mesh->flip_z for @{$self->volumes};
     }
+    $self->set_origin_translation(Slic3r::Pointf3->new(0,0,0));
     $self->invalidate_bounding_box;
 }
 
diff --git a/lib/Slic3r/Point.pm b/lib/Slic3r/Point.pm
index 6d9e0891a..535a97194 100644
--- a/lib/Slic3r/Point.pm
+++ b/lib/Slic3r/Point.pm
@@ -21,4 +21,13 @@ sub new_unscale {
     return $class->new(map Slic3r::Geometry::unscale($_), @_);
 }
 
+package Slic3r::Pointf3;
+use strict;
+use warnings;
+
+sub new_unscale {
+    my $class = shift;
+    return $class->new(map Slic3r::Geometry::unscale($_), @_);
+}
+
 1;
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index b68e191a5..dd96b0e15 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -87,9 +87,12 @@ sub export_gcode {
     if (@{$self->config->post_process}) {
         $self->status_cb->(95, "Running post-processing scripts");
         $self->config->setenv;
-        for (@{$self->config->post_process}) {
-            Slic3r::debugf "  '%s' '%s'\n", $_, $output_file;
-            system($_, $output_file);
+        for my $script (@{$self->config->post_process}) {
+            Slic3r::debugf "  '%s' '%s'\n", $script, $output_file;
+            if (!-x $script) {
+                die "The configured post-processing script is not executable: check permissions. ($script)\n";
+            }
+            system($script, $output_file);
         }
     }
 }
@@ -111,7 +114,8 @@ sub export_svg {
         print "Exporting to $output_file..." unless $params{quiet};
     }
     
-    my $print_size = $self->size;
+    my $print_bb = $self->bounding_box;
+    my $print_size = $print_bb->size;
     print $fh sprintf <<"EOF", unscale($print_size->[X]), unscale($print_size->[Y]);
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/REC-SVG-20010904/DTD/svg10.dtd">
@@ -137,16 +141,20 @@ EOF
     my @previous_layer_slices = ();
     for my $layer (@layers) {
         $layer_id++;
-        # TODO: remove slic3r:z for raft layers
-        printf $fh qq{  <g id="layer%d" slic3r:z="%s">\n}, $layer_id, unscale($layer->slice_z);
+        if ($layer->slice_z == -1) {
+            printf $fh qq{  <g id="layer%d">\n}, $layer_id;
+        } else {
+            printf $fh qq{  <g id="layer%d" slic3r:z="%s">\n}, $layer_id, unscale($layer->slice_z);
+        }
         
         my @current_layer_slices = ();
         # sort slices so that the outermost ones come first
-        my @slices = sort { $a->contour->contains_point($b->contour->[0]) ? 0 : 1 } @{$layer->slices};
-        foreach my $copy (@{$layer->object->copies}) {
+        my @slices = sort { $a->contour->contains_point($b->contour->first_point) ? 0 : 1 } @{$layer->slices};
+        foreach my $copy (@{$layer->object->_shifted_copies}) {
             foreach my $slice (@slices) {
                 my $expolygon = $slice->clone;
                 $expolygon->translate(@$copy);
+                $expolygon->translate(-$print_bb->x_min, -$print_bb->y_min);
                 $print_polygon->($expolygon->contour, 'contour');
                 $print_polygon->($_, 'hole') for @{$expolygon->holes};
                 push @current_layer_slices, $expolygon;
@@ -200,7 +208,7 @@ sub make_skirt {
     # checking whether we need to generate them
     $self->skirt->clear;
     
-    if ($self->config->skirts == 0
+    if (($self->config->skirts == 0 || $self->config->skirt_height == 0)
         && (!$self->config->ooze_prevention || @{$self->extruders} == 1)) {
         $self->set_step_done(STEP_SKIRT);
         return;
@@ -443,7 +451,7 @@ sub expanded_output_filepath {
 }
 
 # This method assigns extruders to the volumes having a material
-# but not having extruders set in the material config.
+# but not having extruders set in the volume config.
 sub auto_assign_extruders {
     my ($self, $model_object) = @_;
     
@@ -454,10 +462,8 @@ sub auto_assign_extruders {
     foreach my $i (0..$#{$model_object->volumes}) {
         my $volume = $model_object->volumes->[$i];
         if ($volume->material_id ne '') {
-            my $material = $model_object->model->get_material($volume->material_id);
-            my $config = $material->config;
             my $extruder_id = $i + 1;
-            $config->set_ifndef('extruder', $extruder_id);
+            $volume->config->set_ifndef('extruder', $extruder_id);
         }
     }
 }
diff --git a/lib/Slic3r/Print/GCode.pm b/lib/Slic3r/Print/GCode.pm
index be90a7998..6b7957a10 100644
--- a/lib/Slic3r/Print/GCode.pm
+++ b/lib/Slic3r/Print/GCode.pm
@@ -169,8 +169,8 @@ sub export {
                 require "Slic3r/SVG.pm";
                 Slic3r::SVG::output(
                     "ooze_prevention.svg",
-                    polygons        => [$outer_skirt],
                     red_polygons    => \@skirts,
+                    polygons        => [$outer_skirt],
                     points          => $gcodegen->ooze_prevention->standby_points,
                 );
             }
@@ -197,7 +197,7 @@ sub export {
                     $gcodegen->set_origin(Slic3r::Pointf->new(map unscale $copy->[$_], X,Y));
                     print $fh $gcodegen->retract;
                     print $fh $gcodegen->travel_to(
-                        $object->_copies_shift->negative,
+                        Slic3r::Point->new(0,0),
                         undef,
                         'move to origin position for next object',
                     );
@@ -321,9 +321,14 @@ sub process_layer {
     }
     
     # set new layer - this will change Z and force a retraction if retract_layer_change is enabled
+    $gcode .= $self->_gcodegen->placeholder_parser->process($self->print->config->before_layer_gcode, {
+        layer_num => $layer->id,
+        layer_z   => $layer->print_z,
+    }) . "\n" if $self->print->config->before_layer_gcode;
     $gcode .= $self->_gcodegen->change_layer($layer);
     $gcode .= $self->_gcodegen->placeholder_parser->process($self->print->config->layer_gcode, {
         layer_num => $layer->id,
+        layer_z   => $layer->print_z,
     }) . "\n" if $self->print->config->layer_gcode;
     
     # extrude skirt
@@ -428,6 +433,8 @@ sub process_layer {
             {
                 my $extruder_id = $region->config->perimeter_extruder-1;
                 foreach my $perimeter_coll (@{$layerm->perimeters}) {
+                    next if $perimeter_coll->empty;  # this shouldn't happen but first_point() would fail
+                    
                     # init by_extruder item only if we actually use the extruder
                     $by_extruder{$extruder_id} //= [];
                     
@@ -450,6 +457,8 @@ sub process_layer {
             # throughout the code). We can redefine the order of such Collections but we have to 
             # do each one completely at once.
             foreach my $fill (@{$layerm->fills}) {
+                next if $fill->empty;  # this shouldn't happen but first_point() would fail
+                
                 # init by_extruder item only if we actually use the extruder
                 my $extruder_id = $fill->[0]->is_solid_infill
                     ? $region->config->solid_infill_extruder-1
diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index 93b69a0fa..dd60a9ec6 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -55,13 +55,14 @@ sub slice {
         
             # raise first object layer Z by the thickness of the raft itself
             # plus the extra distance required by the support material logic
-            $print_z += $self->config->get_value('first_layer_height');
+            my $first_layer_height = $self->config->get_value('first_layer_height');
+            $print_z += $first_layer_height;
             $print_z += $self->config->layer_height * ($self->config->raft_layers - 1);
         
             # at this stage we don't know which nozzles are actually used for the first layer
             # so we compute the average of all of them
             my $nozzle_diameter = sum(@{$self->print->config->nozzle_diameter})/@{$self->print->config->nozzle_diameter};
-            my $distance = Slic3r::Print::SupportMaterial::contact_distance($nozzle_diameter);
+            my $distance = $self->_support_material->contact_distance($first_layer_height, $nozzle_diameter);
         
             # force first layer print_z according to the contact distance
             # (the loop below will raise print_z by such height)
@@ -291,7 +292,7 @@ sub slice {
     while (@{$self->layers} && !@{$self->get_layer(0)->slices}) {
         shift @{$self->layers};
         for (my $i = 0; $i <= $#{$self->layers}; $i++) {
-            $self->get_layer($i)->id( $self->get_layer($i)->id-1 );
+            $self->get_layer($i)->set_id( $self->get_layer($i)->id-1 );
         }
     }
     
@@ -537,6 +538,14 @@ sub generate_support_material {
     }
     $self->print->status_cb->(85, "Generating support material");
     
+    $self->_support_material->generate($self);
+    
+    $self->set_step_done(STEP_SUPPORTMATERIAL);
+}
+
+sub _support_material {
+    my ($self) = @_;
+    
     my $first_layer_flow = Slic3r::Flow->new_from_width(
         width               => ($self->config->first_layer_extrusion_width || $self->config->support_material_extrusion_width),
         role                => FLOW_ROLE_SUPPORT_MATERIAL,
@@ -546,16 +555,13 @@ sub generate_support_material {
         bridge_flow_ratio   => 0,
     );
     
-    my $s = Slic3r::Print::SupportMaterial->new(
+    return Slic3r::Print::SupportMaterial->new(
         print_config        => $self->print->config,
         object_config       => $self->config,
         first_layer_flow    => $first_layer_flow,
         flow                => $self->support_material_flow,
         interface_flow      => $self->support_material_flow(FLOW_ROLE_SUPPORT_MATERIAL_INTERFACE),
     );
-    $s->generate($self);
-    
-    $self->set_step_done(STEP_SUPPORTMATERIAL);
 }
 
 sub detect_surfaces_type {
@@ -572,6 +578,7 @@ sub detect_surfaces_type {
                 my $diff = diff(
                     [ map @$_, @$subject ],
                     [ map @$_, @$clip ],
+                    1,
                 );
                 
                 # collapse very narrow parts (using the safety offset in the diff is not enough)
@@ -616,6 +623,11 @@ sub detect_surfaces_type {
                     S_TYPE_BOTTOMBRIDGE,
                 );
                 
+                # if we have soluble support material, don't bridge
+                if ($self->config->support_material && $self->config->support_material_contact_distance == 0) {
+                    $_->surface_type(S_TYPE_BOTTOM) for @bottom;
+                }
+                
                 # if user requested internal shells, we need to identify surfaces
                 # lying on other slices not belonging to this region
                 if ($self->config->interface_shells) {
@@ -1009,7 +1021,7 @@ sub combine_infill {
                      # Because fill areas for rectilinear and honeycomb are grown 
                      # later to overlap perimeters, we need to counteract that too.
                      + (($type == S_TYPE_INTERNALSOLID || $region->config->fill_pattern =~ /(rectilinear|honeycomb)/)
-                       ? $layerms[-1]->flow(FLOW_ROLE_SOLID_INFILL)->scaled_width * &Slic3r::INFILL_OVERLAP_OVER_SPACING
+                       ? $layerms[-1]->flow(FLOW_ROLE_SOLID_INFILL)->scaled_width
                        : 0)
                      )}, @$intersection;
 
diff --git a/lib/Slic3r/Print/SupportMaterial.pm b/lib/Slic3r/Print/SupportMaterial.pm
index e431f3fb5..4d3e05a9d 100644
--- a/lib/Slic3r/Print/SupportMaterial.pm
+++ b/lib/Slic3r/Print/SupportMaterial.pm
@@ -76,7 +76,7 @@ sub generate {
             $i, # id
             ($i == 0) ? $support_z->[$i] : ($support_z->[$i] - $support_z->[$i-1]), # height
             $support_z->[$i], # print_z
-            -1); # slice_z
+        );
         if ($i >= 1) {
             $object->support_layers->[-2]->set_upper_layer($object->support_layers->[-1]);
             $object->support_layers->[-1]->set_lower_layer($object->support_layers->[-2]);
@@ -270,8 +270,7 @@ sub contact_area {
                 @{$layer->regions};
             my $nozzle_diameter = sum(@nozzle_diameters)/@nozzle_diameters;
             
-            my $contact_z = $layer->print_z - contact_distance($nozzle_diameter);
-            ###$contact_z = $layer->print_z - $layer->height;
+            my $contact_z = $layer->print_z - $self->contact_distance($layer->height, $nozzle_diameter);
             
             # ignore this contact area if it's too low
             next if $contact_z < $self->object_config->get_value('first_layer_height');
@@ -339,12 +338,13 @@ sub support_layers_z {
     # layer_height > nozzle_diameter * 0.75
     my $nozzle_diameter = $self->print_config->get_at('nozzle_diameter', $self->object_config->support_material_extruder-1);
     my $support_material_height = max($max_object_layer_height, $nozzle_diameter * 0.75);
+    my $contact_distance = $self->contact_distance($support_material_height, $nozzle_diameter);
     
     # initialize known, fixed, support layers
     my @z = sort { $a <=> $b }
         @$contact_z,
         @$top_z,  # TODO: why we have this?
-        (map $_ + contact_distance($nozzle_diameter), @$top_z);
+        (map $_ + $contact_distance, @$top_z);
     
     # enforce first layer height
     my $first_layer_height = $self->object_config->get_value('first_layer_height');
@@ -752,8 +752,12 @@ sub generate_toolpaths {
                 # TODO: use offset2_ex()
                 $to_infill = offset_ex([ map @$_, @$to_infill ], -$_flow->scaled_spacing);
             }
-            $filler->spacing($base_flow->spacing);
             
+            # We don't use $base_flow->spacing because we need a constant spacing
+            # value that guarantees that all layers are correctly aligned.
+            $filler->spacing($flow->spacing);
+            
+            my $mm3_per_mm = $base_flow->mm3_per_mm;
             foreach my $expolygon (@$to_infill) {
                 my @p = $filler->fill_surface(
                     Slic3r::Surface->new(expolygon => $expolygon, surface_type => S_TYPE_INTERNAL),
@@ -761,7 +765,6 @@ sub generate_toolpaths {
                     layer_height => $layer->height,
                     complete    => 1,
                 );
-                my $mm3_per_mm = $base_flow->mm3_per_mm;
                 
                 push @paths, map Slic3r::ExtrusionPath->new(
                     polyline    => Slic3r::Polyline->new(@$_),
@@ -906,10 +909,15 @@ sub overlapping_layers {
     } 0..$#$support_z;
 }
 
-# class method
 sub contact_distance {
-    my ($nozzle_diameter) = @_;
-    return $nozzle_diameter * 1.5;
+    my ($self, $layer_height, $nozzle_diameter) = @_;
+    
+    my $extra = $self->object_config->support_material_contact_distance;
+    if ($extra == 0) {
+        return $layer_height;
+    } else {
+        return $nozzle_diameter + $extra;
+    }
 }
 
 1;
diff --git a/lib/Slic3r/Test.pm b/lib/Slic3r/Test.pm
index 32c12ac73..7f1fa5306 100644
--- a/lib/Slic3r/Test.pm
+++ b/lib/Slic3r/Test.pm
@@ -156,7 +156,7 @@ sub init_print {
             $model->duplicate($params{duplicate} // 1, $print->config->min_object_distance);
         }
         $model->arrange_objects($print->config->min_object_distance);
-        $model->center_instances_around_point(Slic3r::Pointf->new(@{$params{print_center}}) // Slic3r::Pointf->new(100,100));
+        $model->center_instances_around_point($params{print_center} ? Slic3r::Pointf->new(@{$params{print_center}}) : Slic3r::Pointf->new(100,100));
         foreach my $model_object (@{$model->objects}) {
             $print->auto_assign_extruders($model_object);
             $print->add_model_object($model_object);
diff --git a/slic3r.pl b/slic3r.pl
index bea11ce1b..84590b197 100755
--- a/slic3r.pl
+++ b/slic3r.pl
@@ -371,6 +371,7 @@ $j
     --end-gcode         Load final G-code from the supplied file. This will overwrite 
                         the default commands (turn off temperature [M104 S0],
                         home X axis [G28 X], disable motors [M84]).
+    --before-layer-gcode  Load before-layer-change G-code from the supplied file (default: nothing).
     --layer-gcode       Load layer-change G-code from the supplied file (default: nothing).
     --toolchange-gcode  Load tool-change G-code from the supplied file (default: nothing).
     --seam-position     Position of loop starting points (random/nearest/aligned, default: $config->{seam_position}).
@@ -405,6 +406,8 @@ $j
                         Spacing between pattern lines (mm, default: $config->{support_material_spacing})
     --support-material-angle
                         Support material angle in degrees (range: 0-90, default: $config->{support_material_angle})
+    --support-material-contact-distance
+                        Vertical distance between object and support material (0+, default: $config->{support_material_contact_distance})
     --support-material-interface-layers
                         Number of perpendicular layers between support material and object (0+, default: $config->{support_material_interface_layers})
     --support-material-interface-spacing
@@ -431,10 +434,10 @@ $j
     
    Retraction options for multi-extruder setups:
     --retract-length-toolchange
-                        Length of retraction in mm when disabling tool (default: $config->{retract_length}[0])
-    --retract-restart-extra-toolchnage
+                        Length of retraction in mm when disabling tool (default: $config->{retract_length_toolchange}[0])
+    --retract-restart-extra-toolchange
                         Additional amount of filament in mm to push after
-                        switching tool (default: $config->{retract_restart_extra}[0])
+                        switching tool (default: $config->{retract_restart_extra_toolchange}[0])
    
    Cooling options:
     --cooling           Enable fan and cooling control
@@ -498,6 +501,7 @@ $j
                         Set a different extrusion width for top infill
     --support-material-extrusion-width
                         Set a different extrusion width for support material
+    --infill-overlap    Overlap between infill and perimeters (default: $config->{infill_overlap})
     --bridge-flow-ratio Multiplier for extrusion when bridging (> 0, default: $config->{bridge_flow_ratio})
   
    Multiple extruder options:
diff --git a/t/fill.t b/t/fill.t
index 63c3c087f..2a7a4521f 100644
--- a/t/fill.t
+++ b/t/fill.t
@@ -206,6 +206,7 @@ for my $pattern (qw(rectilinear honeycomb hilbertcurve concentric)) {
     $config->set('bottom_solid_layers', 0);
     $config->set('infill_extruder', 2);
     $config->set('infill_extrusion_width', 0.5);
+    $config->set('fill_density', 40);
     $config->set('cooling', 0);                 # for preventing speeds from being altered
     $config->set('first_layer_speed', '100%');  # for preventing speeds from being altered
     
diff --git a/t/flow.t b/t/flow.t
index 80fc12c5e..071d290c8 100644
--- a/t/flow.t
+++ b/t/flow.t
@@ -34,7 +34,8 @@ use Slic3r::Test;
         }
     });
     my $E_per_mm_avg = sum(@E_per_mm) / @E_per_mm;
-    ok !(defined first { abs($_ - $E_per_mm_avg) > 0.01 } @E_per_mm),
+    # allow some tolerance because solid rectilinear infill might be adjusted/stretched
+    ok !(defined first { abs($_ - $E_per_mm_avg) > 0.015 } @E_per_mm),
         'first_layer_extrusion_width applies to everything on first layer';
 }
 
diff --git a/t/multi.t b/t/multi.t
index 96703bed2..362f1f7b4 100644
--- a/t/multi.t
+++ b/t/multi.t
@@ -44,7 +44,6 @@ use Slic3r::Test;
                     if $tool_temp[$tool] != $expected_temp + $config->standby_temperature_delta;
                 
                 push @toolchange_points, my $point = Slic3r::Point->new_scale($self->X, $self->Y);
-                $point->translate(map +scale($_), @{ $config->extruder_offset->[$tool] });
             }
             $tool = $1;
         } elsif ($cmd eq 'M104' || $cmd eq 'M109') {
@@ -73,11 +72,11 @@ use Slic3r::Test;
     if (0) {
         require "Slic3r/SVG.pm";
         Slic3r::SVG::output(
-            "ooze_prevention.svg",
+            "ooze_prevention_test.svg",
             no_arrows   => 1,
             polygons    => [$convex_hull],
-            points      => \@toolchange_points,
             red_points  => \@t,
+            points      => \@toolchange_points,
         );
     }
     
@@ -169,6 +168,7 @@ use Slic3r::Test;
 
 {
     my $model = stacked_cubes();
+    my $object = $model->objects->[0];
     
     my $config = Slic3r::Config->new_from_defaults;
     $config->set('layer_height', 0.4);
@@ -176,8 +176,8 @@ use Slic3r::Test;
     $config->set('skirts', 0);
     my $print = Slic3r::Test::init_print($model, config => $config);
     
-    is $model->get_material('lower')->config->extruder, 1, 'auto_assign_extruders() assigned correct extruder to first volume';
-    is $model->get_material('upper')->config->extruder, 2, 'auto_assign_extruders() assigned correct extruder to second volume';
+    is $object->volumes->[0]->config->extruder, 1, 'auto_assign_extruders() assigned correct extruder to first volume';
+    is $object->volumes->[1]->config->extruder, 2, 'auto_assign_extruders() assigned correct extruder to second volume';
     
     my $tool = undef;
     my %T0 = my %T1 = ();  # Z => 1
diff --git a/t/pressure.t b/t/pressure.t
index fd9045c82..6bbb81d84 100644
--- a/t/pressure.t
+++ b/t/pressure.t
@@ -29,7 +29,7 @@ use Slic3r::Test;
         }
     });
     
-    ok abs($retracted) < epsilon, 'all retractions are compensated';
+    ok abs($retracted) < 0.01, 'all retractions are compensated';
 }
 
 
diff --git a/t/shells.t b/t/shells.t
index a133e1d33..a12858ae0 100644
--- a/t/shells.t
+++ b/t/shells.t
@@ -143,6 +143,7 @@ use Slic3r::Test;
     $config->set('top_solid_layers', 3);
     $config->set('solid_infill_speed', 99);
     $config->set('top_solid_infill_speed', 99);
+    $config->set('bridge_speed', 99);
     
     my $print = Slic3r::Test::init_print('sloping_hole', config => $config);
     my %solid_layers = ();  # Z => 1
diff --git a/t/skirt_brim.t b/t/skirt_brim.t
index c7377abf8..878a78840 100644
--- a/t/skirt_brim.t
+++ b/t/skirt_brim.t
@@ -1,4 +1,4 @@
-use Test::More tests => 5;
+use Test::More tests => 6;
 use strict;
 use warnings;
 
@@ -79,6 +79,15 @@ use Slic3r::Test;
     ok Slic3r::Test::gcode($print), 'successful G-code generation when skirt is smaller than brim width';
 }
 
+{
+    my $config = Slic3r::Config->new_from_defaults;
+    $config->set('skirts', 1);
+    $config->set('skirt_height', 0);
+    
+    my $print = Slic3r::Test::init_print('20mm_cube', config => $config);
+    ok Slic3r::Test::gcode($print), 'successful G-code generation when skirt_height = 0 and skirts > 0';
+}
+
 {
     my $config = Slic3r::Config->new_from_defaults;
     $config->set('layer_height', 0.4);
diff --git a/t/support.t b/t/support.t
index edf5476c5..54d5ef700 100644
--- a/t/support.t
+++ b/t/support.t
@@ -30,7 +30,7 @@ use Slic3r::Test;
             first_layer_flow    => $flow,
         );
         my $support_z = $support->support_layers_z(\@contact_z, \@top_z, $config->layer_height);
-        my $expected_top_spacing = Slic3r::Print::SupportMaterial::contact_distance($config->nozzle_diameter->[0]);
+        my $expected_top_spacing = $support->contact_distance($config->layer_height, $config->nozzle_diameter->[0]);
         
         is $support_z->[0], $config->first_layer_height,
             'first layer height is honored';
diff --git a/utils/view-mesh.pl b/utils/view-mesh.pl
index 25fbf3638..687a56224 100644
--- a/utils/view-mesh.pl
+++ b/utils/view-mesh.pl
@@ -12,7 +12,7 @@ BEGIN {
 use Getopt::Long qw(:config no_auto_abbrev);
 use Slic3r;
 use Slic3r::GUI;
-use Slic3r::GUI::PreviewCanvas;
+use Slic3r::GUI::3DScene;
 $|++;
 
 my %opt = ();
@@ -31,11 +31,12 @@ my %opt = ();
     
     # make sure all objects have at least one defined instance
     $model->add_default_instances;
+    $_->center_around_origin for @{$model->objects};  # and align to Z = 0
     
     my $app = Slic3r::ViewMesh->new;
     $app->{canvas}->enable_picking(1);
     $app->{canvas}->enable_moving($opt{enable_moving});
-    $app->{canvas}->load_object($model->objects->[0]);
+    $app->{canvas}->load_object($model, 0);
     $app->{canvas}->set_auto_bed_shape;
     $app->{canvas}->zoom_to_volumes;
     $app->{canvas}->SetCuttingPlane($opt{cut}) if defined $opt{cut};
@@ -66,7 +67,7 @@ sub OnInit {
     my $frame = Wx::Frame->new(undef, -1, 'Mesh Viewer', [-1, -1], [500, 400]);
     my $panel = Wx::Panel->new($frame, -1);
     
-    $self->{canvas} = Slic3r::GUI::PreviewCanvas->new($panel);
+    $self->{canvas} = Slic3r::GUI::3DScene->new($panel);
     
     my $sizer = Wx::BoxSizer->new(wxVERTICAL);
     $sizer->Add($self->{canvas}, 1, wxEXPAND, 0);
diff --git a/utils/view-toolpaths.pl b/utils/view-toolpaths.pl
index 847ba61d9..7e1d305bc 100755
--- a/utils/view-toolpaths.pl
+++ b/utils/view-toolpaths.pl
@@ -12,7 +12,7 @@ BEGIN {
 use Getopt::Long qw(:config no_auto_abbrev);
 use Slic3r;
 use Slic3r::GUI;
-use Slic3r::GUI::PreviewCanvas;
+use Slic3r::GUI::3DScene;
 $|++;
 
 my %opt = ();
@@ -82,13 +82,13 @@ sub OnInit {
     
     my $canvas;
     if ($d3) {
-        $canvas = Slic3r::GUI::PreviewCanvas->new($panel);
-        $canvas->print($print);
-        
+        $canvas = Slic3r::GUI::3DScene->new($panel);
         $canvas->set_bed_shape($print->config->bed_shape);
         
         foreach my $object (@{$print->objects}) {
-            $canvas->load_object($object->model_object);
+            #$canvas->load_print_object_slices($object);
+            $canvas->load_print_object_toolpaths($object);
+            #$canvas->load_object($object->model_object);
         }
         $canvas->zoom_to_volumes;
     } else {
diff --git a/xs/MANIFEST b/xs/MANIFEST
index fb06bec85..0b42a4852 100644
--- a/xs/MANIFEST
+++ b/xs/MANIFEST
@@ -1677,6 +1677,8 @@ src/libslic3r/GCodeWriter.cpp
 src/libslic3r/GCodeWriter.hpp
 src/libslic3r/Geometry.cpp
 src/libslic3r/Geometry.hpp
+src/libslic3r/GUI/3DScene.cpp
+src/libslic3r/GUI/3DScene.hpp
 src/libslic3r/Layer.cpp
 src/libslic3r/Layer.hpp
 src/libslic3r/LayerRegion.cpp
@@ -1765,6 +1767,7 @@ xsp/Flow.xsp
 xsp/GCodeSender.xsp
 xsp/GCodeWriter.xsp
 xsp/Geometry.xsp
+xsp/GUI_3DScene.xsp
 xsp/Layer.xsp
 xsp/Line.xsp
 xsp/Model.xsp
diff --git a/xs/lib/Slic3r/XS.pm b/xs/lib/Slic3r/XS.pm
index 9ac0b35e9..842f4526f 100644
--- a/xs/lib/Slic3r/XS.pm
+++ b/xs/lib/Slic3r/XS.pm
@@ -23,6 +23,11 @@ use overload
     '@{}' => sub { [ $_[0]->x, $_[0]->y, $_[0]->z ] },  #,
     'fallback' => 1;
 
+sub pp {
+    my ($self) = @_;
+    return [ @$self ];
+}
+
 package Slic3r::Pointf;
 use overload
     '@{}' => sub { $_[0]->arrayref },
@@ -33,6 +38,11 @@ use overload
     '@{}' => sub { [ $_[0]->x, $_[0]->y, $_[0]->z ] },  #,
     'fallback' => 1;
 
+sub pp {
+    my ($self) = @_;
+    return [ @$self ];
+}
+
 package Slic3r::ExPolygon;
 use overload
     '@{}' => sub { $_[0]->arrayref },
@@ -186,6 +196,9 @@ sub new {
     return $self;
 }
 
+package Slic3r::GUI::_3DScene::GLVertexArray;
+sub CLONE_SKIP { 1 }
+
 package main;
 for my $class (qw(
         Slic3r::BridgeDetector
diff --git a/xs/src/libslic3r/BridgeDetector.cpp b/xs/src/libslic3r/BridgeDetector.cpp
index 5eeca86a5..dfc145422 100644
--- a/xs/src/libslic3r/BridgeDetector.cpp
+++ b/xs/src/libslic3r/BridgeDetector.cpp
@@ -89,8 +89,7 @@ BridgeDetector::detect_angle()
     {
         Polygons pp = this->expolygon;
         for (Polygons::const_iterator p = pp.begin(); p != pp.end(); ++p) {
-            Lines lines;
-            p->lines(&lines);
+            Lines lines = p->lines();
             for (Lines::const_iterator line = lines.begin(); line != lines.end(); ++line)
                 angles.push_back(line->direction());
         }
diff --git a/xs/src/libslic3r/Config.hpp b/xs/src/libslic3r/Config.hpp
index 0d86294a3..313b524fa 100644
--- a/xs/src/libslic3r/Config.hpp
+++ b/xs/src/libslic3r/Config.hpp
@@ -295,18 +295,21 @@ class ConfigOptionPoints : public ConfigOption, public ConfigOptionVector<Pointf
     };
     
     bool deserialize(std::string str) {
-        std::vector<Pointf> values;
+        this->values.clear();
         std::istringstream is(str);
         std::string point_str;
         while (std::getline(is, point_str, ',')) {
             Pointf point;
             std::istringstream iss(point_str);
-            iss >> point.x;
-            iss.ignore(std::numeric_limits<std::streamsize>::max(), 'x');
-            iss >> point.y;
-            values.push_back(point);
+            std::string coord_str;
+            if (std::getline(iss, coord_str, 'x')) {
+                std::istringstream(coord_str) >> point.x;
+                if (std::getline(iss, coord_str, 'x')) {
+                    std::istringstream(coord_str) >> point.y;
+                }
+            }
+            this->values.push_back(point);
         }
-        this->values = values;
         return true;
     };
 };
diff --git a/xs/src/libslic3r/ExPolygon.cpp b/xs/src/libslic3r/ExPolygon.cpp
index 2c5246aad..a03447bba 100644
--- a/xs/src/libslic3r/ExPolygon.cpp
+++ b/xs/src/libslic3r/ExPolygon.cpp
@@ -129,14 +129,20 @@ ExPolygon::simplify_p(double tolerance) const
     pp.reserve(this->holes.size() + 1);
     
     // contour
-    Polygon p = this->contour;
-    p.points = MultiPoint::_douglas_peucker(p.points, tolerance);
-    pp.push_back(p);
+    {
+        Polygon p = this->contour;
+        p.points.push_back(p.points.front());
+        p.points = MultiPoint::_douglas_peucker(p.points, tolerance);
+        p.points.pop_back();
+        pp.push_back(p);
+    }
     
     // holes
     for (Polygons::const_iterator it = this->holes.begin(); it != this->holes.end(); ++it) {
-        p = *it;
+        Polygon p = *it;
+        p.points.push_back(p.points.front());
         p.points = MultiPoint::_douglas_peucker(p.points, tolerance);
+        p.points.pop_back();
         pp.push_back(p);
     }
     simplify_polygons(pp, &pp);
@@ -167,9 +173,11 @@ ExPolygon::medial_axis(double max_width, double min_width, Polylines* polylines)
     Slic3r::Geometry::MedialAxis ma(max_width, min_width);
     
     // populate list of segments for the Voronoi diagram
-    this->contour.lines(&ma.lines);
-    for (Polygons::const_iterator hole = this->holes.begin(); hole != this->holes.end(); ++hole)
-        hole->lines(&ma.lines);
+    ma.lines = this->contour.lines();
+    for (Polygons::const_iterator hole = this->holes.begin(); hole != this->holes.end(); ++hole) {
+        Lines lines = hole->lines();
+        ma.lines.insert(ma.lines.end(), lines.begin(), lines.end());
+    }
     
     // compute the Voronoi diagram
     ma.build(polylines);
@@ -384,10 +392,11 @@ ExPolygon::triangulate_p2t(Polygons* polygons) const
 Lines
 ExPolygon::lines() const
 {
-    Lines lines;
-    this->contour.lines(&lines);
-    for (Polygons::const_iterator h = this->holes.begin(); h != this->holes.end(); ++h)
-        h->lines(&lines);
+    Lines lines = this->contour.lines();
+    for (Polygons::const_iterator h = this->holes.begin(); h != this->holes.end(); ++h) {
+        Lines hole_lines = h->lines();
+        lines.insert(lines.end(), hole_lines.begin(), hole_lines.end());
+    }
     return lines;
 }
 
diff --git a/xs/src/libslic3r/ExPolygonCollection.cpp b/xs/src/libslic3r/ExPolygonCollection.cpp
index aaa747d8d..3b47c29b3 100644
--- a/xs/src/libslic3r/ExPolygonCollection.cpp
+++ b/xs/src/libslic3r/ExPolygonCollection.cpp
@@ -92,13 +92,13 @@ ExPolygonCollection::simplify(double tolerance)
     this->expolygons = expp;
 }
 
-void
-ExPolygonCollection::convex_hull(Polygon* hull) const
+Polygon
+ExPolygonCollection::convex_hull() const
 {
     Points pp;
     for (ExPolygons::const_iterator it = this->expolygons.begin(); it != this->expolygons.end(); ++it)
         pp.insert(pp.end(), it->contour.points.begin(), it->contour.points.end());
-    Slic3r::Geometry::convex_hull(pp, hull);
+    return Slic3r::Geometry::convex_hull(pp);
 }
 
 Lines
diff --git a/xs/src/libslic3r/ExPolygonCollection.hpp b/xs/src/libslic3r/ExPolygonCollection.hpp
index cca6064d5..86f77cbcb 100644
--- a/xs/src/libslic3r/ExPolygonCollection.hpp
+++ b/xs/src/libslic3r/ExPolygonCollection.hpp
@@ -28,7 +28,7 @@ class ExPolygonCollection
     template <class T> bool contains(const T &item) const;
     bool contains_b(const Point &point) const;
     void simplify(double tolerance);
-    void convex_hull(Polygon* hull) const;
+    Polygon convex_hull() const;
     Lines lines() const;
 };
 
diff --git a/xs/src/libslic3r/ExtrusionEntity.cpp b/xs/src/libslic3r/ExtrusionEntity.cpp
index 843dfda29..f4ef37c13 100644
--- a/xs/src/libslic3r/ExtrusionEntity.cpp
+++ b/xs/src/libslic3r/ExtrusionEntity.cpp
@@ -164,11 +164,12 @@ ExtrusionPath::gcode(Extruder* extruder, double e, double F,
     return stream.str();
 }
 
-ExtrusionLoop::operator Polygon() const
+Polygons
+ExtrusionPath::grow() const
 {
-    Polygon polygon;
-    this->polygon(&polygon);
-    return polygon;
+    Polygons pp;
+    offset(this->polyline, &pp, +this->width/2);
+    return pp;
 }
 
 ExtrusionLoop*
@@ -180,8 +181,7 @@ ExtrusionLoop::clone() const
 bool
 ExtrusionLoop::make_clockwise()
 {
-    Polygon polygon = *this;
-    bool was_ccw = polygon.is_counter_clockwise();
+    bool was_ccw = this->polygon().is_counter_clockwise();
     if (was_ccw) this->reverse();
     return was_ccw;
 }
@@ -189,8 +189,7 @@ ExtrusionLoop::make_clockwise()
 bool
 ExtrusionLoop::make_counter_clockwise()
 {
-    Polygon polygon = *this;
-    bool was_cw = polygon.is_clockwise();
+    bool was_cw = this->polygon().is_clockwise();
     if (was_cw) this->reverse();
     return was_cw;
 }
@@ -215,13 +214,15 @@ ExtrusionLoop::last_point() const
     return this->paths.back().polyline.points.back();  // which coincides with first_point(), by the way
 }
 
-void
-ExtrusionLoop::polygon(Polygon* polygon) const
+Polygon
+ExtrusionLoop::polygon() const
 {
+    Polygon polygon;
     for (ExtrusionPaths::const_iterator path = this->paths.begin(); path != this->paths.end(); ++path) {
         // for each polyline, append all points except the last one (because it coincides with the first one of the next polyline)
-        polygon->points.insert(polygon->points.end(), path->polyline.points.begin(), path->polyline.points.end()-1);
+        polygon.points.insert(polygon.points.end(), path->polyline.points.begin(), path->polyline.points.end()-1);
     }
+    return polygon;
 }
 
 double
@@ -363,6 +364,17 @@ ExtrusionLoop::is_solid_infill() const
         || this->paths.front().role == erTopSolidInfill;
 }
 
+Polygons
+ExtrusionLoop::grow() const
+{
+    Polygons pp;
+    for (ExtrusionPaths::const_iterator path = this->paths.begin(); path != this->paths.end(); ++path) {
+        Polygons path_pp = path->grow();
+        pp.insert(pp.end(), path_pp.begin(), path_pp.end());
+    }
+    return pp;
+}
+
 #ifdef SLIC3RXS
 REGISTER_CLASS(ExtrusionLoop, "ExtrusionLoop");
 #endif
diff --git a/xs/src/libslic3r/ExtrusionEntity.hpp b/xs/src/libslic3r/ExtrusionEntity.hpp
index c40291190..323d935a1 100644
--- a/xs/src/libslic3r/ExtrusionEntity.hpp
+++ b/xs/src/libslic3r/ExtrusionEntity.hpp
@@ -43,6 +43,7 @@ class ExtrusionEntity
     virtual void reverse() = 0;
     virtual Point first_point() const = 0;
     virtual Point last_point() const = 0;
+    virtual Polygons grow() const = 0;
 };
 
 typedef std::vector<ExtrusionEntity*> ExtrusionEntitiesPtr;
@@ -73,6 +74,7 @@ class ExtrusionPath : public ExtrusionEntity
     std::string gcode(Extruder* extruder, double e, double F,
         double xofs, double yofs, std::string extrusion_axis,
         std::string gcode_line_suffix) const;
+    Polygons grow() const;
 
     private:
     void _inflate_collection(const Polylines &polylines, ExtrusionEntityCollection* collection) const;
@@ -90,14 +92,13 @@ class ExtrusionLoop : public ExtrusionEntity
     bool is_loop() const {
         return true;
     };
-    operator Polygon() const;
     ExtrusionLoop* clone() const;
     bool make_clockwise();
     bool make_counter_clockwise();
     void reverse();
     Point first_point() const;
     Point last_point() const;
-    void polygon(Polygon* polygon) const;
+    Polygon polygon() const;
     double length() const;
     bool split_at_vertex(const Point &point);
     void split_at(const Point &point);
@@ -106,6 +107,7 @@ class ExtrusionLoop : public ExtrusionEntity
     bool is_perimeter() const;
     bool is_infill() const;
     bool is_solid_infill() const;
+    Polygons grow() const;
 };
 
 }
diff --git a/xs/src/libslic3r/ExtrusionEntityCollection.cpp b/xs/src/libslic3r/ExtrusionEntityCollection.cpp
index 4e3c596cf..4ceef0387 100644
--- a/xs/src/libslic3r/ExtrusionEntityCollection.cpp
+++ b/xs/src/libslic3r/ExtrusionEntityCollection.cpp
@@ -110,6 +110,17 @@ ExtrusionEntityCollection::chained_path_from(Point start_near, ExtrusionEntityCo
     }
 }
 
+Polygons
+ExtrusionEntityCollection::grow() const
+{
+    Polygons pp;
+    for (ExtrusionEntitiesPtr::const_iterator it = this->entities.begin(); it != this->entities.end(); ++it) {
+        Polygons entity_pp = (*it)->grow();
+        pp.insert(pp.end(), entity_pp.begin(), entity_pp.end());
+    }
+    return pp;
+}
+
 #ifdef SLIC3RXS
 // there is no ExtrusionLoop::Collection or ExtrusionEntity::Collection
 REGISTER_CLASS(ExtrusionEntityCollection, "ExtrusionPath::Collection");
diff --git a/xs/src/libslic3r/ExtrusionEntityCollection.hpp b/xs/src/libslic3r/ExtrusionEntityCollection.hpp
index bc660611b..be557bb5f 100644
--- a/xs/src/libslic3r/ExtrusionEntityCollection.hpp
+++ b/xs/src/libslic3r/ExtrusionEntityCollection.hpp
@@ -22,6 +22,7 @@ class ExtrusionEntityCollection : public ExtrusionEntity
     void reverse();
     Point first_point() const;
     Point last_point() const;
+    Polygons grow() const;
 };
 
 }
diff --git a/xs/src/libslic3r/Flow.cpp b/xs/src/libslic3r/Flow.cpp
index b9af18184..f91caed4b 100644
--- a/xs/src/libslic3r/Flow.cpp
+++ b/xs/src/libslic3r/Flow.cpp
@@ -32,6 +32,7 @@ Flow::new_from_spacing(float spacing, float nozzle_diameter, float height, bool
     if (height <= 0 && !bridge) CONFESS("Invalid flow height supplied to new_from_spacing()");
 
     float w = Flow::_width_from_spacing(spacing, nozzle_diameter, height, bridge);
+    if (bridge) height = w;
     return Flow(w, height, nozzle_diameter, bridge);
 }
 
diff --git a/xs/src/libslic3r/GCodeWriter.cpp b/xs/src/libslic3r/GCodeWriter.cpp
index 0fe15809e..9aa7616a6 100644
--- a/xs/src/libslic3r/GCodeWriter.cpp
+++ b/xs/src/libslic3r/GCodeWriter.cpp
@@ -60,16 +60,6 @@ GCodeWriter::preamble()
         } else {
             gcode << "M82 ; use absolute distances for extrusion\n";
         }
-        if (this->config.use_volumetric_e && this->config.start_gcode.value.find("M200") == std::string::npos) {
-            for (std::map<unsigned int,Extruder>::const_iterator it = this->extruders.begin(); it != this->extruders.end(); ++it) {
-                unsigned int extruder_id = it->first;
-                gcode << "M200 D" << E_NUM(this->config.filament_diameter.get_at(extruder_id));
-                if (this->multiple_extruders || extruder_id != 0) {
-                    gcode << " T" << extruder_id;
-                }
-                gcode << " ; set filament diameter\n";
-            }
-        }
         gcode << this->reset_e(true);
     }
     
diff --git a/xs/src/libslic3r/GUI/3DScene.cpp b/xs/src/libslic3r/GUI/3DScene.cpp
new file mode 100644
index 000000000..5f61b37b3
--- /dev/null
+++ b/xs/src/libslic3r/GUI/3DScene.cpp
@@ -0,0 +1,248 @@
+#include "3DScene.hpp"
+
+namespace Slic3r {
+
+// caller is responsible for supplying NO lines with zero length
+void
+_3DScene::_extrusionentity_to_verts_do(const Lines &lines, const std::vector<double> &widths,
+        const std::vector<double> &heights, bool closed, double top_z, const Point &copy,
+        GLVertexArray* qverts, GLVertexArray* tverts)
+{
+    /* It looks like it's faster without reserving capacity...
+    // each segment has 4 quads, thus 16 vertices; + 2 caps
+    qverts->reserve_more(3 * 4 * (4 * lines.size() + 2));
+    
+    // two triangles for each corner
+    tverts->reserve_more(3 * 3 * 2 * (lines.size() + 1));
+    */
+    
+    Line prev_line;
+    Pointf prev_b1, prev_b2;
+    Vectorf3 prev_xy_left_normal, prev_xy_right_normal;
+    
+    // loop once more in case of closed loops
+    bool first_done = false;
+    for (size_t i = 0; i <= lines.size(); ++i) {
+        if (i == lines.size()) i = 0;
+        
+        const Line &line = lines.at(i);
+        if (i == 0 && first_done && !closed) break;
+        
+        double len = line.length();
+        double unscaled_len = unscale(len);
+        
+        double bottom_z = top_z - heights.at(i);
+        double middle_z = (top_z + bottom_z) / 2;
+        double dist = widths.at(i)/2;  // scaled
+        
+        Vectorf v = Vectorf::new_unscale(line.vector());
+        v.scale(1/unscaled_len);
+        
+        Pointf a = Pointf::new_unscale(line.a);
+        Pointf b = Pointf::new_unscale(line.b);
+        Pointf a1 = a;
+        Pointf a2 = a;
+        a1.translate(+dist*v.y, -dist*v.x);
+        a2.translate(-dist*v.y, +dist*v.x);
+        Pointf b1 = b;
+        Pointf b2 = b;
+        b1.translate(+dist*v.y, -dist*v.x);
+        b2.translate(-dist*v.y, +dist*v.x);
+        
+        // calculate new XY normals
+        Vector n = line.normal();
+        Vectorf3 xy_right_normal = Vectorf3::new_unscale(n.x, n.y, 0);
+        xy_right_normal.scale(1/unscaled_len);
+        Vectorf3 xy_left_normal = xy_right_normal;
+        xy_left_normal.scale(-1);
+        
+        if (first_done) {
+            // if we're making a ccw turn, draw the triangles on the right side, otherwise draw them on the left side
+            double ccw = line.b.ccw(prev_line);
+            if (ccw > EPSILON) {
+                // top-right vertex triangle between previous line and this one
+                {
+                    // use the normal going to the right calculated for the previous line
+                    tverts->push_norm(prev_xy_right_normal);
+                    tverts->push_vert(prev_b1.x, prev_b1.y, middle_z);
+            
+                    // use the normal going to the right calculated for this line
+                    tverts->push_norm(xy_right_normal);
+                    tverts->push_vert(a1.x, a1.y, middle_z);
+            
+                    // normal going upwards
+                    tverts->push_norm(0,0,1);
+                    tverts->push_vert(a.x, a.y, top_z);
+                }
+                // bottom-right vertex triangle between previous line and this one
+                {
+                    // use the normal going to the right calculated for the previous line
+                    tverts->push_norm(prev_xy_right_normal);
+                    tverts->push_vert(prev_b1.x, prev_b1.y, middle_z);
+            
+                    // normal going downwards
+                    tverts->push_norm(0,0,-1);
+                    tverts->push_vert(a.x, a.y, bottom_z);
+            
+                    // use the normal going to the right calculated for this line
+                    tverts->push_norm(xy_right_normal);
+                    tverts->push_vert(a1.x, a1.y, middle_z);
+                }
+            } else if (ccw < -EPSILON) {
+                // top-left vertex triangle between previous line and this one
+                {
+                    // use the normal going to the left calculated for the previous line
+                    tverts->push_norm(prev_xy_left_normal);
+                    tverts->push_vert(prev_b2.x, prev_b2.y, middle_z);
+            
+                    // normal going upwards
+                    tverts->push_norm(0,0,1);
+                    tverts->push_vert(a.x, a.y, top_z);
+            
+                    // use the normal going to the right calculated for this line
+                    tverts->push_norm(xy_left_normal);
+                    tverts->push_vert(a2.x, a2.y, middle_z);
+                }
+                // bottom-left vertex triangle between previous line and this one
+                {
+                    // use the normal going to the left calculated for the previous line
+                    tverts->push_norm(prev_xy_left_normal);
+                    tverts->push_vert(prev_b2.x, prev_b2.y, middle_z);
+            
+                    // use the normal going to the right calculated for this line
+                    tverts->push_norm(xy_left_normal);
+                    tverts->push_vert(a2.x, a2.y, middle_z);
+            
+                    // normal going downwards
+                    tverts->push_norm(0,0,-1);
+                    tverts->push_vert(a.x, a.y, bottom_z);
+                }
+            }
+        }
+        
+        // if this was the extra iteration we were only interested in the triangles
+        if (first_done && i == 0) break;
+        
+        prev_line = line;
+        prev_b1 = b1;
+        prev_b2 = b2;
+        prev_xy_right_normal = xy_right_normal;
+        prev_xy_left_normal  = xy_left_normal;
+        
+        if (!closed) {
+            // terminate open paths with caps
+            if (i == 0) {
+                // normal pointing downwards
+                qverts->push_norm(0,0,-1);
+                qverts->push_vert(a.x, a.y, bottom_z);
+            
+                // normal pointing to the right
+                qverts->push_norm(xy_right_normal);
+                qverts->push_vert(a1.x, a1.y, middle_z);
+            
+                // normal pointing upwards
+                qverts->push_norm(0,0,1);
+                qverts->push_vert(a.x, a.y, top_z);
+            
+                // normal pointing to the left
+                qverts->push_norm(xy_left_normal);
+                qverts->push_vert(a2.x, a2.y, middle_z);
+            }
+            // we don't use 'else' because both cases are true if we have only one line
+            if (i == lines.size()-1) {
+                // normal pointing downwards
+                qverts->push_norm(0,0,-1);
+                qverts->push_vert(b.x, b.y, bottom_z);
+            
+                // normal pointing to the left
+                qverts->push_norm(xy_left_normal);
+                qverts->push_vert(b2.x, b2.y, middle_z);
+            
+                // normal pointing upwards
+                qverts->push_norm(0,0,1);
+                qverts->push_vert(b.x, b.y, top_z);
+            
+                // normal pointing to the right
+                qverts->push_norm(xy_right_normal);
+                qverts->push_vert(b1.x, b1.y, middle_z);
+            }
+        }
+        
+        // bottom-right face
+        {
+            // normal going downwards
+            qverts->push_norm(0,0,-1);
+            qverts->push_norm(0,0,-1);
+            qverts->push_vert(a.x, a.y, bottom_z);
+            qverts->push_vert(b.x, b.y, bottom_z);
+            
+            qverts->push_norm(xy_right_normal);
+            qverts->push_norm(xy_right_normal);
+            qverts->push_vert(b1.x, b1.y, middle_z);
+            qverts->push_vert(a1.x, a1.y, middle_z);
+        }
+        
+        // top-right face
+        {
+            qverts->push_norm(xy_right_normal);
+            qverts->push_norm(xy_right_normal);
+            qverts->push_vert(a1.x, a1.y, middle_z);
+            qverts->push_vert(b1.x, b1.y, middle_z);
+            
+            // normal going upwards
+            qverts->push_norm(0,0,1);
+            qverts->push_norm(0,0,1);
+            qverts->push_vert(b.x, b.y, top_z);
+            qverts->push_vert(a.x, a.y, top_z);
+        }
+         
+        // top-left face
+        {
+            qverts->push_norm(0,0,1);
+            qverts->push_norm(0,0,1);
+            qverts->push_vert(a.x, a.y, top_z);
+            qverts->push_vert(b.x, b.y, top_z);
+            
+            qverts->push_norm(xy_left_normal);
+            qverts->push_norm(xy_left_normal);
+            qverts->push_vert(b2.x, b2.y, middle_z);
+            qverts->push_vert(a2.x, a2.y, middle_z);
+        }
+        
+        // bottom-left face
+        {
+            qverts->push_norm(xy_left_normal);
+            qverts->push_norm(xy_left_normal);
+            qverts->push_vert(a2.x, a2.y, middle_z);
+            qverts->push_vert(b2.x, b2.y, middle_z);
+            
+            // normal going downwards
+            qverts->push_norm(0,0,-1);
+            qverts->push_norm(0,0,-1);
+            qverts->push_vert(b.x, b.y, bottom_z);
+            qverts->push_vert(a.x, a.y, bottom_z);
+        }
+        
+        first_done = true;
+    }
+}
+
+void
+GLVertexArray::load_mesh(const TriangleMesh &mesh)
+{
+    this->reserve_more(3 * 3 * mesh.facets_count());
+    
+    for (int i = 0; i < mesh.stl.stats.number_of_facets; ++i) {
+        stl_facet &facet = mesh.stl.facet_start[i];
+        for (int j = 0; j <= 2; ++j) {
+            this->push_norm(facet.normal.x, facet.normal.y, facet.normal.z);
+            this->push_vert(facet.vertex[j].x, facet.vertex[j].y, facet.vertex[j].z);
+        }
+    }
+}
+
+#ifdef SLIC3RXS
+REGISTER_CLASS(GLVertexArray, "GUI::_3DScene::GLVertexArray");
+#endif
+
+}
diff --git a/xs/src/libslic3r/GUI/3DScene.hpp b/xs/src/libslic3r/GUI/3DScene.hpp
new file mode 100644
index 000000000..df2531778
--- /dev/null
+++ b/xs/src/libslic3r/GUI/3DScene.hpp
@@ -0,0 +1,56 @@
+#ifndef slic3r_3DScene_hpp_
+#define slic3r_3DScene_hpp_
+
+#include <myinit.h>
+#include "../Point.hpp"
+#include "../Line.hpp"
+#include "../TriangleMesh.hpp"
+
+namespace Slic3r {
+
+class GLVertexArray {
+    public:
+    std::vector<float> verts, norms;
+    
+    void reserve(size_t len) {
+        this->verts.reserve(len);
+        this->norms.reserve(len);
+    };
+    void reserve_more(size_t len) {
+        len += this->verts.size();
+        this->reserve(len);
+    };
+    void push_vert(const Pointf3 &point) {
+        this->verts.push_back(point.x);
+        this->verts.push_back(point.y);
+        this->verts.push_back(point.z);
+    };
+    void push_vert(float x, float y, float z) {
+        this->verts.push_back(x);
+        this->verts.push_back(y);
+        this->verts.push_back(z);
+    };
+    void push_norm(const Pointf3 &point) {
+        this->norms.push_back(point.x);
+        this->norms.push_back(point.y);
+        this->norms.push_back(point.z);
+    };
+    void push_norm(float x, float y, float z) {
+        this->norms.push_back(x);
+        this->norms.push_back(y);
+        this->norms.push_back(z);
+    };
+    void load_mesh(const TriangleMesh &mesh);
+};
+
+class _3DScene
+{
+    public:
+    static void _extrusionentity_to_verts_do(const Lines &lines, const std::vector<double> &widths,
+        const std::vector<double> &heights, bool closed, double top_z, const Point &copy,
+        GLVertexArray* qverts, GLVertexArray* tverts);
+};
+
+}
+
+#endif
diff --git a/xs/src/libslic3r/Geometry.cpp b/xs/src/libslic3r/Geometry.cpp
index e30e73702..3dc11c0cb 100644
--- a/xs/src/libslic3r/Geometry.cpp
+++ b/xs/src/libslic3r/Geometry.cpp
@@ -1,4 +1,5 @@
 #include "Geometry.hpp"
+#include "ClipperUtils.hpp"
 #include "ExPolygon.hpp"
 #include "Line.hpp"
 #include "PolylineCollection.hpp"
@@ -25,42 +26,45 @@ sort_points (Point a, Point b)
 }
 
 /* This implementation is based on Andrew's monotone chain 2D convex hull algorithm */
-void
-convex_hull(Points points, Polygon* hull)
+Polygon
+convex_hull(Points points)
 {
     assert(points.size() >= 3);
     // sort input points
     std::sort(points.begin(), points.end(), sort_points);
     
     int n = points.size(), k = 0;
-    hull->points.resize(2*n);
+    Polygon hull;
+    hull.points.resize(2*n);
 
     // Build lower hull
     for (int i = 0; i < n; i++) {
-        while (k >= 2 && points[i].ccw(hull->points[k-2], hull->points[k-1]) <= 0) k--;
-        hull->points[k++] = points[i];
+        while (k >= 2 && points[i].ccw(hull.points[k-2], hull.points[k-1]) <= 0) k--;
+        hull.points[k++] = points[i];
     }
 
     // Build upper hull
     for (int i = n-2, t = k+1; i >= 0; i--) {
-        while (k >= t && points[i].ccw(hull->points[k-2], hull->points[k-1]) <= 0) k--;
-        hull->points[k++] = points[i];
+        while (k >= t && points[i].ccw(hull.points[k-2], hull.points[k-1]) <= 0) k--;
+        hull.points[k++] = points[i];
     }
 
-    hull->points.resize(k);
+    hull.points.resize(k);
     
-    assert( hull->points.front().coincides_with(hull->points.back()) );
-    hull->points.pop_back();
+    assert( hull.points.front().coincides_with(hull.points.back()) );
+    hull.points.pop_back();
+    
+    return hull;
 }
 
-void
-convex_hull(const Polygons &polygons, Polygon* hull)
+Polygon
+convex_hull(const Polygons &polygons)
 {
     Points pp;
     for (Polygons::const_iterator p = polygons.begin(); p != polygons.end(); ++p) {
         pp.insert(pp.end(), p->points.begin(), p->points.end());
     }
-    convex_hull(pp, hull);
+    return convex_hull(pp);
 }
 
 /* accepts an arrayref of points and returns a list of indices
@@ -143,6 +147,20 @@ deg2rad(double angle)
     return PI * angle / 180.0;
 }
 
+void
+simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval)
+{
+    Polygons pp;
+    for (Polygons::const_iterator it = polygons.begin(); it != polygons.end(); ++it) {
+        Polygon p = *it;
+        p.points.push_back(p.points.front());
+        p.points = MultiPoint::_douglas_peucker(p.points, tolerance);
+        p.points.pop_back();
+        pp.push_back(p);
+    }
+    Slic3r::simplify_polygons(pp, retval);
+}
+
 Line
 MedialAxis::edge_to_line(const VD::edge_type &edge) const
 {
diff --git a/xs/src/libslic3r/Geometry.hpp b/xs/src/libslic3r/Geometry.hpp
index e7f2f08f3..c2cacfa33 100644
--- a/xs/src/libslic3r/Geometry.hpp
+++ b/xs/src/libslic3r/Geometry.hpp
@@ -11,8 +11,8 @@ using boost::polygon::voronoi_diagram;
 
 namespace Slic3r { namespace Geometry {
 
-void convex_hull(Points points, Polygon* hull);
-void convex_hull(const Polygons &polygons, Polygon* hull);
+Polygon convex_hull(Points points);
+Polygon convex_hull(const Polygons &polygons);
 void chained_path(const Points &points, std::vector<Points::size_type> &retval, Point start_near);
 void chained_path(const Points &points, std::vector<Points::size_type> &retval);
 template<class T> void chained_path_items(Points &points, T &items, T &retval);
@@ -21,6 +21,7 @@ template<class T> bool contains(const std::vector<T> &vector, const Point &point
 double rad2deg(double angle);
 double rad2deg_dir(double angle);
 double deg2rad(double angle);
+void simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval);
 
 class MedialAxis {
     public:
diff --git a/xs/src/libslic3r/Layer.cpp b/xs/src/libslic3r/Layer.cpp
index 38935fced..2e1a8c50e 100644
--- a/xs/src/libslic3r/Layer.cpp
+++ b/xs/src/libslic3r/Layer.cpp
@@ -6,7 +6,7 @@
 
 namespace Slic3r {
 
-Layer::Layer(int id, PrintObject *object, coordf_t height, coordf_t print_z,
+Layer::Layer(size_t id, PrintObject *object, coordf_t height, coordf_t print_z,
         coordf_t slice_z)
 :   _id(id),
     _object(object),
@@ -35,12 +35,18 @@ Layer::~Layer()
     this->clear_regions();
 }
 
-int
-Layer::id()
+size_t
+Layer::id() const
 {
     return this->_id;
 }
 
+void
+Layer::set_id(size_t id)
+{
+    this->_id = id;
+}
+
 PrintObject*
 Layer::object()
 {
@@ -147,7 +153,7 @@ REGISTER_CLASS(Layer, "Layer");
 #endif
 
 
-SupportLayer::SupportLayer(int id, PrintObject *object, coordf_t height,
+SupportLayer::SupportLayer(size_t id, PrintObject *object, coordf_t height,
         coordf_t print_z, coordf_t slice_z)
 :   Layer(id, object, height, print_z, slice_z)
 {
diff --git a/xs/src/libslic3r/Layer.hpp b/xs/src/libslic3r/Layer.hpp
index 5f6a6baa0..6dd6e81a5 100644
--- a/xs/src/libslic3r/Layer.hpp
+++ b/xs/src/libslic3r/Layer.hpp
@@ -56,6 +56,7 @@ class LayerRegion
     
     Flow flow(FlowRole role, bool bridge = false, double width = -1) const;
     void merge_slices();
+    void prepare_fill_surfaces();
     
     private:
     Layer *_layer;
@@ -72,7 +73,8 @@ class Layer {
     friend class PrintObject;
 
     public:
-    int id();
+    size_t id() const;
+    void set_id(size_t id);
     PrintObject* object();
 
     Layer *upper_layer;
@@ -97,11 +99,11 @@ class Layer {
     template <class T> bool any_bottom_region_slice_contains(const T &item) const;
     
     protected:
-    int _id;     // sequential number of layer, 0-based
+    size_t _id;     // sequential number of layer, 0-based
     PrintObject *_object;
 
 
-    Layer(int id, PrintObject *object, coordf_t height, coordf_t print_z,
+    Layer(size_t id, PrintObject *object, coordf_t height, coordf_t print_z,
         coordf_t slice_z);
     virtual ~Layer();
 
@@ -119,7 +121,7 @@ class SupportLayer : public Layer {
     ExtrusionEntityCollection support_interface_fills;
 
     protected:
-    SupportLayer(int id, PrintObject *object, coordf_t height, coordf_t print_z,
+    SupportLayer(size_t id, PrintObject *object, coordf_t height, coordf_t print_z,
         coordf_t slice_z);
     virtual ~SupportLayer();
 };
diff --git a/xs/src/libslic3r/LayerRegion.cpp b/xs/src/libslic3r/LayerRegion.cpp
index 7b8e77f5a..e988566a8 100644
--- a/xs/src/libslic3r/LayerRegion.cpp
+++ b/xs/src/libslic3r/LayerRegion.cpp
@@ -53,6 +53,38 @@ LayerRegion::merge_slices()
         this->slices.surfaces.push_back(Surface(stInternal, *expoly));
 }
 
+void
+LayerRegion::prepare_fill_surfaces()
+{
+    /*  Note: in order to make the psPrepareInfill step idempotent, we should never
+        alter fill_surfaces boundaries on which our idempotency relies since that's
+        the only meaningful information returned by psPerimeters. */
+    
+    // if no solid layers are requested, turn top/bottom surfaces to internal
+    if (this->_region->config.top_solid_layers == 0) {
+        for (Surfaces::iterator surface = this->fill_surfaces.surfaces.begin(); surface != this->fill_surfaces.surfaces.end(); ++surface) {
+            if (surface->surface_type == stTop)
+                surface->surface_type = stInternal;
+        }
+    }
+    if (this->_region->config.bottom_solid_layers == 0) {
+        for (Surfaces::iterator surface = this->fill_surfaces.surfaces.begin(); surface != this->fill_surfaces.surfaces.end(); ++surface) {
+            if (surface->surface_type == stBottom || surface->surface_type == stBottomBridge)
+                surface->surface_type = stInternal;
+        }
+    }
+        
+    // turn too small internal regions into solid regions according to the user setting
+    if (this->_region->config.fill_density.value > 0) {
+        // scaling an area requires two calls!
+        double min_area = scale_(scale_(this->_region->config.solid_infill_below_area.value));
+        for (Surfaces::iterator surface = this->fill_surfaces.surfaces.begin(); surface != this->fill_surfaces.surfaces.end(); ++surface) {
+            if (surface->surface_type == stInternal && surface->area() <= min_area)
+                surface->surface_type = stInternalSolid;
+        }
+    }
+}
+
 #ifdef SLIC3RXS
 REGISTER_CLASS(LayerRegion, "Layer::Region");
 #endif
diff --git a/xs/src/libslic3r/Line.cpp b/xs/src/libslic3r/Line.cpp
index 3cce6c971..84ba10a5b 100644
--- a/xs/src/libslic3r/Line.cpp
+++ b/xs/src/libslic3r/Line.cpp
@@ -64,10 +64,10 @@ Line::length() const
     return this->a.distance_to(this->b);
 }
 
-Point*
+Point
 Line::midpoint() const
 {
-    return new Point ((this->a.x + this->b.x) / 2.0, (this->a.y + this->b.y) / 2.0);
+    return Point((this->a.x + this->b.x) / 2.0, (this->a.y + this->b.y) / 2.0);
 }
 
 void
@@ -89,6 +89,23 @@ Line::point_at(double distance) const
     return p;
 }
 
+bool
+Line::intersection_infinite(const Line &other, Point* point) const
+{
+    Vector x = this->a.vector_to(other.a);
+    Vector d1 = this->vector();
+    Vector d2 = other.vector();
+
+    double cross = d1.x * d2.y - d1.y * d2.x;
+    if (std::fabs(cross) < EPSILON)
+        return false;
+
+    double t1 = (x.x * d2.y - x.y * d2.x)/cross;
+    point->x = this->a.x + d1.x * t1;
+    point->y = this->a.y + d1.y * t1;
+    return true;
+}
+
 bool
 Line::coincides_with(const Line &line) const
 {
@@ -201,6 +218,13 @@ Linef3::intersect_plane(double z) const
     );
 }
 
+void
+Linef3::scale(double factor)
+{
+    this->a.scale(factor);
+    this->b.scale(factor);
+}
+
 #ifdef SLIC3RXS
 REGISTER_CLASS(Linef3, "Linef3");
 #endif
diff --git a/xs/src/libslic3r/Line.hpp b/xs/src/libslic3r/Line.hpp
index 76c385ce6..327ff4d1e 100644
--- a/xs/src/libslic3r/Line.hpp
+++ b/xs/src/libslic3r/Line.hpp
@@ -26,9 +26,10 @@ class Line
     void rotate(double angle, const Point &center);
     void reverse();
     double length() const;
-    Point* midpoint() const;
+    Point midpoint() const;
     void point_at(double distance, Point* point) const;
     Point point_at(double distance) const;
+    bool intersection_infinite(const Line &other, Point* point) const;
     bool coincides_with(const Line &line) const;
     double distance_to(const Point &point) const;
     bool parallel_to(double angle) const;
@@ -47,6 +48,15 @@ class Line
     #endif
 };
 
+class Linef
+{
+    public:
+    Pointf a;
+    Pointf b;
+    Linef() {};
+    explicit Linef(Pointf _a, Pointf _b): a(_a), b(_b) {};
+};
+
 class Linef3
 {
     public:
@@ -55,6 +65,7 @@ class Linef3
     Linef3() {};
     explicit Linef3(Pointf3 _a, Pointf3 _b): a(_a), b(_b) {};
     Pointf3 intersect_plane(double z) const;
+    void scale(double factor);
     
     #ifdef SLIC3RXS
     void from_SV(SV* line_sv);
diff --git a/xs/src/libslic3r/Model.cpp b/xs/src/libslic3r/Model.cpp
index 40926eb93..d03a2916c 100644
--- a/xs/src/libslic3r/Model.cpp
+++ b/xs/src/libslic3r/Model.cpp
@@ -130,8 +130,7 @@ Model::duplicate_objects_grid(unsigned int x, unsigned int y, coordf_t distance)
     ModelObject* object = this->objects.front();
     object->clear_instances();
 
-    BoundingBoxf3 bb;
-    object->bounding_box(&bb);
+    BoundingBoxf3 bb = object->bounding_box();
     Sizef3 size = bb.size();
 
     for (unsigned int x_copy = 1; x_copy <= x; ++x_copy) {
@@ -174,21 +173,20 @@ Model::add_default_instances()
 }
 
 // this returns the bounding box of the *transformed* instances
-void
-Model::bounding_box(BoundingBoxf3* bb)
+BoundingBoxf3
+Model::bounding_box() const
 {
+    BoundingBoxf3 bb;
     for (ModelObjectPtrs::const_iterator o = this->objects.begin(); o != this->objects.end(); ++o) {
-        BoundingBoxf3 obb;
-        (*o)->bounding_box(&obb);
-        bb->merge(obb);
+        bb.merge((*o)->bounding_box());
     }
+    return bb;
 }
 
 void
 Model::center_instances_around_point(const Pointf &point)
 {
-    BoundingBoxf3 bb;
-    this->bounding_box(&bb);
+    BoundingBoxf3 bb = this->bounding_box();
     
     Sizef3 size = bb.size();
     double shift_x = -bb.min.x + point.x - size.x/2;
@@ -205,8 +203,7 @@ Model::center_instances_around_point(const Pointf &point)
 void
 Model::align_instances_to_origin()
 {
-    BoundingBoxf3 bb;
-    this->bounding_box(&bb);
+    BoundingBoxf3 bb = this->bounding_box();
     
     Pointf new_center = (Pointf)bb.size();
     new_center.translate(-new_center.x/2, -new_center.y/2);
@@ -222,25 +219,25 @@ Model::translate(coordf_t x, coordf_t y, coordf_t z)
 }
 
 // flattens everything to a single mesh
-void
-Model::mesh(TriangleMesh* mesh) const
+TriangleMesh
+Model::mesh() const
 {
+    TriangleMesh mesh;
     for (ModelObjectPtrs::const_iterator o = this->objects.begin(); o != this->objects.end(); ++o) {
-        TriangleMesh omesh;
-        (*o)->mesh(&omesh);
-        mesh->merge(omesh);
+        mesh.merge((*o)->mesh());
     }
+    return mesh;
 }
 
 // flattens everything to a single mesh
-void
-Model::raw_mesh(TriangleMesh* mesh) const
+TriangleMesh
+Model::raw_mesh() const
 {
+    TriangleMesh mesh;
     for (ModelObjectPtrs::const_iterator o = this->objects.begin(); o != this->objects.end(); ++o) {
-        TriangleMesh omesh;
-        (*o)->raw_mesh(&omesh);
-        mesh->merge(omesh);
+        mesh.merge((*o)->raw_mesh());
     }
+    return mesh;
 }
 
 #ifdef SLIC3RXS
@@ -393,11 +390,11 @@ ModelObject::clear_instances()
 }
 
 // this returns the bounding box of the *transformed* instances
-void
-ModelObject::bounding_box(BoundingBoxf3* bb)
+BoundingBoxf3
+ModelObject::bounding_box()
 {
     if (!this->_bounding_box_valid) this->update_bounding_box();
-    *bb = this->_bounding_box;
+    return this->_bounding_box;
 }
 
 void
@@ -409,40 +406,40 @@ ModelObject::invalidate_bounding_box()
 void
 ModelObject::update_bounding_box()
 {
-    TriangleMesh mesh;
-    this->mesh(&mesh);
-    
-    mesh.bounding_box(&this->_bounding_box);
+    this->_bounding_box = this->mesh().bounding_box();
     this->_bounding_box_valid = true;
 }
 
 // flattens all volumes and instances into a single mesh
-void
-ModelObject::mesh(TriangleMesh* mesh) const
+TriangleMesh
+ModelObject::mesh() const
 {
-    TriangleMesh raw_mesh;
-    this->raw_mesh(&raw_mesh);
-    
+    TriangleMesh mesh;
+    TriangleMesh raw_mesh = this->raw_mesh();
     
     for (ModelInstancePtrs::const_iterator i = this->instances.begin(); i != this->instances.end(); ++i) {
         TriangleMesh m = raw_mesh;
         (*i)->transform_mesh(&m);
-        mesh->merge(m);
+        mesh.merge(m);
     }
+    return mesh;
 }
 
-void
-ModelObject::raw_mesh(TriangleMesh* mesh) const
+TriangleMesh
+ModelObject::raw_mesh() const
 {
+    TriangleMesh mesh;
     for (ModelVolumePtrs::const_iterator v = this->volumes.begin(); v != this->volumes.end(); ++v) {
         if ((*v)->modifier) continue;
-        mesh->merge((*v)->mesh);
+        mesh.merge((*v)->mesh);
     }
+    return mesh;
 }
 
-void
-ModelObject::raw_bounding_box(BoundingBoxf3* bb) const
+BoundingBoxf3
+ModelObject::raw_bounding_box() const
 {
+    BoundingBoxf3 bb;
     for (ModelVolumePtrs::const_iterator v = this->volumes.begin(); v != this->volumes.end(); ++v) {
         if ((*v)->modifier) continue;
         TriangleMesh mesh = (*v)->mesh;
@@ -450,22 +447,18 @@ ModelObject::raw_bounding_box(BoundingBoxf3* bb) const
         if (this->instances.empty()) CONFESS("Can't call raw_bounding_box() with no instances");
         this->instances.front()->transform_mesh(&mesh, true);
         
-        BoundingBoxf3 mbb;
-        mesh.bounding_box(&mbb);
-        bb->merge(mbb);
+        bb.merge(mesh.bounding_box());
     }
+    return bb;
 }
 
 // this returns the bounding box of the *transformed* given instance
-void
-ModelObject::instance_bounding_box(size_t instance_idx, BoundingBoxf3* bb) const
+BoundingBoxf3
+ModelObject::instance_bounding_box(size_t instance_idx) const
 {
-    TriangleMesh mesh;
-    this->raw_mesh(&mesh);
-    
+    TriangleMesh mesh = this->raw_mesh();
     this->instances[instance_idx]->transform_mesh(&mesh);
-    
-    mesh.bounding_box(bb);
+    return mesh.bounding_box();
 }
 
 void
@@ -473,12 +466,7 @@ ModelObject::center_around_origin()
 {
     // calculate the displacements needed to 
     // center this object around the origin
-    BoundingBoxf3 bb;
-    {
-        TriangleMesh mesh;
-        this->raw_mesh(&mesh);
-        mesh.bounding_box(&bb);
-    }
+    BoundingBoxf3 bb = this->raw_mesh().bounding_box();
     
     // first align to origin on XYZ
     Vectorf3 vector(-bb.min.x, -bb.min.y, -bb.min.z);
@@ -520,6 +508,9 @@ ModelObject::scale(const Pointf3 &versor)
     for (ModelVolumePtrs::const_iterator v = this->volumes.begin(); v != this->volumes.end(); ++v) {
         (*v)->mesh.scale(versor);
     }
+    
+    // reset origin translation since it doesn't make sense anymore
+    this->origin_translation = Pointf3(0,0,0);
     this->invalidate_bounding_box();
 }
 
diff --git a/xs/src/libslic3r/Model.hpp b/xs/src/libslic3r/Model.hpp
index 62bb38bfc..2ec7c5b08 100644
--- a/xs/src/libslic3r/Model.hpp
+++ b/xs/src/libslic3r/Model.hpp
@@ -54,12 +54,12 @@ class Model
     // void duplicate(size_t copies_num, coordf_t distance, const BoundingBox &bb);
     bool has_objects_with_no_instances() const;
     bool add_default_instances();
-    void bounding_box(BoundingBoxf3* bb);
+    BoundingBoxf3 bounding_box() const;
     void center_instances_around_point(const Pointf &point);
     void align_instances_to_origin();
     void translate(coordf_t x, coordf_t y, coordf_t z);
-    void mesh(TriangleMesh* mesh) const;
-    void raw_mesh(TriangleMesh* mesh) const;
+    TriangleMesh mesh() const;
+    TriangleMesh raw_mesh() const;
     // std::string get_material_name(t_model_material_id material_id);
 
     
@@ -97,7 +97,7 @@ class ModelObject
     
     /* This vector accumulates the total translation applied to the object by the
         center_around_origin() method. Callers might want to apply the same translation
-        to new volumes before adding them to this object in order to preset alignment
+        to new volumes before adding them to this object in order to preserve alignment
         when user expects that. */
     Pointf3 origin_translation;
     
@@ -118,13 +118,13 @@ class ModelObject
     void delete_last_instance();
     void clear_instances();
 
-    void bounding_box(BoundingBoxf3* bb);
+    BoundingBoxf3 bounding_box();
     void invalidate_bounding_box();
 
-    void mesh(TriangleMesh* mesh) const;
-    void raw_mesh(TriangleMesh* mesh) const;
-    void raw_bounding_box(BoundingBoxf3* bb) const;
-    void instance_bounding_box(size_t instance_idx, BoundingBoxf3* bb) const;
+    TriangleMesh mesh() const;
+    TriangleMesh raw_mesh() const;
+    BoundingBoxf3 raw_bounding_box() const;
+    BoundingBoxf3 instance_bounding_box(size_t instance_idx) const;
     void center_around_origin();
     void translate(const Vectorf3 &vector);
     void translate(coordf_t x, coordf_t y, coordf_t z);
diff --git a/xs/src/libslic3r/MotionPlanner.cpp b/xs/src/libslic3r/MotionPlanner.cpp
index 47e058497..124f96891 100644
--- a/xs/src/libslic3r/MotionPlanner.cpp
+++ b/xs/src/libslic3r/MotionPlanner.cpp
@@ -82,17 +82,18 @@ MotionPlanner::get_env(size_t island_idx) const
     }
 }
 
-void
-MotionPlanner::shortest_path(const Point &from, const Point &to, Polyline* polyline)
+Polyline
+MotionPlanner::shortest_path(const Point &from, const Point &to)
 {
     // lazy generation of configuration space
     if (!this->initialized) this->initialize();
     
     // if we have an empty configuration space, return a straight move
     if (this->islands.empty()) {
-        polyline->points.push_back(from);
-        polyline->points.push_back(to);
-        return;
+        Polyline p;
+        p.points.push_back(from);
+        p.points.push_back(to);
+        return p;
     }
     
     // Are both points in the same island?
@@ -102,9 +103,10 @@ MotionPlanner::shortest_path(const Point &from, const Point &to, Polyline* polyl
             // since both points are in the same island, is a direct move possible?
             // if so, we avoid generating the visibility environment
             if (island->contains(Line(from, to))) {
-                polyline->points.push_back(from);
-                polyline->points.push_back(to);
-                return;
+                Polyline p;
+                p.points.push_back(from);
+                p.points.push_back(to);
+                return p;
             }
             island_idx = island - this->islands.begin();
             break;
@@ -116,9 +118,10 @@ MotionPlanner::shortest_path(const Point &from, const Point &to, Polyline* polyl
     if (env.expolygons.empty()) {
         // if this environment is empty (probably because it's too small), perform straight move
         // and avoid running the algorithms on empty dataset
-        polyline->points.push_back(from);
-        polyline->points.push_back(to);
-        return; // bye bye
+        Polyline p;
+        p.points.push_back(from);
+        p.points.push_back(to);
+        return p; // bye bye
     }
     
     // Now check whether points are inside the environment.
@@ -137,10 +140,10 @@ MotionPlanner::shortest_path(const Point &from, const Point &to, Polyline* polyl
     
     // perform actual path search
     MotionPlannerGraph* graph = this->init_graph(island_idx);
-    graph->shortest_path(graph->find_node(inner_from), graph->find_node(inner_to), polyline);
+    Polyline polyline = graph->shortest_path(graph->find_node(inner_from), graph->find_node(inner_to));
     
-    polyline->points.insert(polyline->points.begin(), from);
-    polyline->points.push_back(to);
+    polyline.points.insert(polyline.points.begin(), from);
+    polyline.points.push_back(to);
     
     {
         // grow our environment slightly in order for simplify_by_visibility()
@@ -149,7 +152,7 @@ MotionPlanner::shortest_path(const Point &from, const Point &to, Polyline* polyl
         offset(env, &grown_env.expolygons, +SCALED_EPSILON);
         
         // remove unnecessary vertices
-        polyline->simplify_by_visibility(grown_env);
+        polyline.simplify_by_visibility(grown_env);
     }
     
     /*
@@ -171,6 +174,8 @@ MotionPlanner::shortest_path(const Point &from, const Point &to, Polyline* polyl
         svg.draw(*polyline, "red");
         svg.Close();
     */
+    
+    return polyline;
 }
 
 Point
@@ -310,11 +315,11 @@ MotionPlannerGraph::find_node(const Point &point) const
     return point.nearest_point_index(this->nodes);
 }
 
-void
-MotionPlannerGraph::shortest_path(size_t from, size_t to, Polyline* polyline)
+Polyline
+MotionPlannerGraph::shortest_path(size_t from, size_t to)
 {
     // this prevents a crash in case for some reason we got here with an empty adjacency list
-    if (this->adjacency_list.empty()) return;
+    if (this->adjacency_list.empty()) return Polyline();
     
     const weight_t max_weight = std::numeric_limits<weight_t>::infinity();
     
@@ -379,10 +384,12 @@ MotionPlannerGraph::shortest_path(size_t from, size_t to, Polyline* polyline)
         }
     }
     
+    Polyline polyline;
     for (node_t vertex = to; vertex != -1; vertex = previous[vertex])
-        polyline->points.push_back(this->nodes[vertex]);
-    polyline->points.push_back(this->nodes[from]);
-    polyline->reverse();
+        polyline.points.push_back(this->nodes[vertex]);
+    polyline.points.push_back(this->nodes[from]);
+    polyline.reverse();
+    return polyline;
 }
 
 #ifdef SLIC3RXS
diff --git a/xs/src/libslic3r/MotionPlanner.hpp b/xs/src/libslic3r/MotionPlanner.hpp
index c1617e184..608f01681 100644
--- a/xs/src/libslic3r/MotionPlanner.hpp
+++ b/xs/src/libslic3r/MotionPlanner.hpp
@@ -21,7 +21,7 @@ class MotionPlanner
     public:
     MotionPlanner(const ExPolygons &islands);
     ~MotionPlanner();
-    void shortest_path(const Point &from, const Point &to, Polyline* polyline);
+    Polyline shortest_path(const Point &from, const Point &to);
     size_t islands_count() const;
     
     private:
@@ -58,7 +58,7 @@ class MotionPlannerGraph
     //std::map<std::pair<size_t,size_t>, double> edges;
     void add_edge(size_t from, size_t to, double weight);
     size_t find_node(const Point &point) const;
-    void shortest_path(size_t from, size_t to, Polyline* polyline);
+    Polyline shortest_path(size_t from, size_t to);
 };
 
 }
diff --git a/xs/src/libslic3r/MultiPoint.cpp b/xs/src/libslic3r/MultiPoint.cpp
index 6ed430cf7..614306e42 100644
--- a/xs/src/libslic3r/MultiPoint.cpp
+++ b/xs/src/libslic3r/MultiPoint.cpp
@@ -83,10 +83,21 @@ MultiPoint::has_boundary_point(const Point &point) const
     return dist < SCALED_EPSILON;
 }
 
-void
-MultiPoint::bounding_box(BoundingBox* bb) const
+BoundingBox
+MultiPoint::bounding_box() const
 {
-    *bb = BoundingBox(this->points);
+    return BoundingBox(this->points);
+}
+
+void
+MultiPoint::remove_duplicate_points()
+{
+    for (size_t i = 1; i < this->points.size(); ++i) {
+        if (this->points.at(i).coincides_with(this->points.at(i-1))) {
+            this->points.erase(this->points.begin() + i);
+            --i;
+        }
+    }
 }
 
 Points
diff --git a/xs/src/libslic3r/MultiPoint.hpp b/xs/src/libslic3r/MultiPoint.hpp
index 96c2876f5..12c500836 100644
--- a/xs/src/libslic3r/MultiPoint.hpp
+++ b/xs/src/libslic3r/MultiPoint.hpp
@@ -31,7 +31,8 @@ class MultiPoint
     bool is_valid() const;
     int find_point(const Point &point) const;
     bool has_boundary_point(const Point &point) const;
-    void bounding_box(BoundingBox* bb) const;
+    BoundingBox bounding_box() const;
+    void remove_duplicate_points();
     
     static Points _douglas_peucker(const Points &points, const double tolerance);
     
diff --git a/xs/src/libslic3r/Point.hpp b/xs/src/libslic3r/Point.hpp
index a3283c260..327199690 100644
--- a/xs/src/libslic3r/Point.hpp
+++ b/xs/src/libslic3r/Point.hpp
@@ -9,6 +9,7 @@
 namespace Slic3r {
 
 class Line;
+class Linef;
 class MultiPoint;
 class Point;
 class Pointf;
@@ -82,6 +83,12 @@ class Pointf
     coordf_t x;
     coordf_t y;
     explicit Pointf(coordf_t _x = 0, coordf_t _y = 0): x(_x), y(_y) {};
+    static Pointf new_unscale(coord_t x, coord_t y) {
+        return Pointf(unscale(x), unscale(y));
+    };
+    static Pointf new_unscale(const Point &p) {
+        return Pointf(unscale(p.x), unscale(p.y));
+    };
     void scale(double factor);
     void translate(double x, double y);
     void rotate(double angle, const Pointf &center);
@@ -100,6 +107,9 @@ class Pointf3 : public Pointf
     public:
     coordf_t z;
     explicit Pointf3(coordf_t _x = 0, coordf_t _y = 0, coordf_t _z = 0): Pointf(_x, _y), z(_z) {};
+    static Pointf3 new_unscale(coord_t x, coord_t y, coord_t z) {
+        return Pointf3(unscale(x), unscale(y), unscale(z));
+    };
     void scale(double factor);
     void translate(const Vectorf3 &vector);
     void translate(double x, double y, double z);
diff --git a/xs/src/libslic3r/Polygon.cpp b/xs/src/libslic3r/Polygon.cpp
index 4c73de092..c6fb91131 100644
--- a/xs/src/libslic3r/Polygon.cpp
+++ b/xs/src/libslic3r/Polygon.cpp
@@ -14,9 +14,7 @@ Polygon::operator Polygons() const
 
 Polygon::operator Polyline() const
 {
-    Polyline polyline;
-    this->split_at_first_point(&polyline);
-    return polyline;
+    return this->split_at_first_point();
 }
 
 Point&
@@ -41,55 +39,49 @@ Lines
 Polygon::lines() const
 {
     Lines lines;
-    this->lines(&lines);
+    lines.reserve(this->points.size());
+    for (Points::const_iterator it = this->points.begin(); it != this->points.end()-1; ++it) {
+        lines.push_back(Line(*it, *(it + 1)));
+    }
+    lines.push_back(Line(this->points.back(), this->points.front()));
     return lines;
 }
 
-void
-Polygon::lines(Lines* lines) const
-{
-    lines->reserve(lines->size() + this->points.size());
-    for (Points::const_iterator it = this->points.begin(); it != this->points.end()-1; ++it) {
-        lines->push_back(Line(*it, *(it + 1)));
-    }
-    lines->push_back(Line(this->points.back(), this->points.front()));
-}
-
-void
-Polygon::split_at_vertex(const Point &point, Polyline* polyline) const
+Polyline
+Polygon::split_at_vertex(const Point &point) const
 {
     // find index of point
     for (Points::const_iterator it = this->points.begin(); it != this->points.end(); ++it) {
         if (it->coincides_with(point)) {
-            this->split_at_index(it - this->points.begin(), polyline);
-            return;
+            return this->split_at_index(it - this->points.begin());
         }
     }
     CONFESS("Point not found");
+    return Polyline();
 }
 
-void
-Polygon::split_at_index(int index, Polyline* polyline) const
-{
-    polyline->points.reserve(this->points.size() + 1);
-    for (Points::const_iterator it = this->points.begin() + index; it != this->points.end(); ++it)
-        polyline->points.push_back(*it);
-    for (Points::const_iterator it = this->points.begin(); it != this->points.begin() + index + 1; ++it)
-        polyline->points.push_back(*it);
-}
-
-void
-Polygon::split_at_first_point(Polyline* polyline) const
-{
-    this->split_at_index(0, polyline);
-}
-
-void
-Polygon::equally_spaced_points(double distance, Points* points) const
+Polyline
+Polygon::split_at_index(int index) const
 {
     Polyline polyline;
-    this->split_at_first_point(&polyline);
-    polyline.equally_spaced_points(distance, points);
+    polyline.points.reserve(this->points.size() + 1);
+    for (Points::const_iterator it = this->points.begin() + index; it != this->points.end(); ++it)
+        polyline.points.push_back(*it);
+    for (Points::const_iterator it = this->points.begin(); it != this->points.begin() + index + 1; ++it)
+        polyline.points.push_back(*it);
+    return polyline;
+}
+
+Polyline
+Polygon::split_at_first_point() const
+{
+    return this->split_at_index(0);
+}
+
+Points
+Polygon::equally_spaced_points(double distance) const
+{
+    return this->split_at_first_point().equally_spaced_points(distance);
 }
 
 double
@@ -155,6 +147,7 @@ Polygon::contains(const Point &point) const
     return result;
 }
 
+// this only works on CCW polygons as CW will be ripped out by Clipper's simplify_polygons()
 Polygons
 Polygon::simplify(double tolerance) const
 {
@@ -203,8 +196,7 @@ Polygon::centroid() const
     double x_temp = 0;
     double y_temp = 0;
     
-    Polyline polyline;
-    this->split_at_first_point(&polyline);
+    Polyline polyline = this->split_at_first_point();
     for (Points::const_iterator point = polyline.points.begin(); point != polyline.points.end() - 1; ++point) {
         x_temp += (double)( point->x + (point+1)->x ) * ( (double)point->x*(point+1)->y - (double)(point+1)->x*point->y );
         y_temp += (double)( point->y + (point+1)->y ) * ( (double)point->x*(point+1)->y - (double)(point+1)->x*point->y );
@@ -227,55 +219,49 @@ Polygon::wkt() const
 }
 
 // find all concave vertices (i.e. having an internal angle greater than the supplied angle) */
-void
-Polygon::concave_points(double angle, Points* points) const
+Points
+Polygon::concave_points(double angle) const
 {
+    Points points;
     angle = 2*PI - angle;
     
     // check whether first point forms a concave angle
     if (this->points.front().ccw_angle(this->points.back(), *(this->points.begin()+1)) <= angle)
-        points->push_back(this->points.front());
+        points.push_back(this->points.front());
     
     // check whether points 1..(n-1) form concave angles
     for (Points::const_iterator p = this->points.begin()+1; p != this->points.end()-1; ++p) {
-        if (p->ccw_angle(*(p-1), *(p+1)) <= angle) points->push_back(*p);
+        if (p->ccw_angle(*(p-1), *(p+1)) <= angle) points.push_back(*p);
     }
     
     // check whether last point forms a concave angle
     if (this->points.back().ccw_angle(*(this->points.end()-2), this->points.front()) <= angle)
-        points->push_back(this->points.back());
-}
-
-void
-Polygon::concave_points(Points* points) const
-{
-    this->concave_points(PI, points);
+        points.push_back(this->points.back());
+    
+    return points;
 }
 
 // find all convex vertices (i.e. having an internal angle smaller than the supplied angle) */
-void
-Polygon::convex_points(double angle, Points* points) const
+Points
+Polygon::convex_points(double angle) const
 {
+    Points points;
     angle = 2*PI - angle;
     
     // check whether first point forms a convex angle
     if (this->points.front().ccw_angle(this->points.back(), *(this->points.begin()+1)) >= angle)
-        points->push_back(this->points.front());
+        points.push_back(this->points.front());
     
     // check whether points 1..(n-1) form convex angles
     for (Points::const_iterator p = this->points.begin()+1; p != this->points.end()-1; ++p) {
-        if (p->ccw_angle(*(p-1), *(p+1)) >= angle) points->push_back(*p);
+        if (p->ccw_angle(*(p-1), *(p+1)) >= angle) points.push_back(*p);
     }
     
     // check whether last point forms a convex angle
     if (this->points.back().ccw_angle(*(this->points.end()-2), this->points.front()) >= angle)
-        points->push_back(this->points.back());
-}
-
-void
-Polygon::convex_points(Points* points) const
-{
-    this->convex_points(PI, points);
+        points.push_back(this->points.back());
+    
+    return points;
 }
 
 #ifdef SLIC3RXS
diff --git a/xs/src/libslic3r/Polygon.hpp b/xs/src/libslic3r/Polygon.hpp
index 778825f3e..bed80e177 100644
--- a/xs/src/libslic3r/Polygon.hpp
+++ b/xs/src/libslic3r/Polygon.hpp
@@ -24,11 +24,10 @@ class Polygon : public MultiPoint {
     explicit Polygon(const Points &points): MultiPoint(points) {};
     Point last_point() const;
     Lines lines() const;
-    void lines(Lines* lines) const;
-    void split_at_vertex(const Point &point, Polyline* polyline) const;
-    void split_at_index(int index, Polyline* polyline) const;
-    void split_at_first_point(Polyline* polyline) const;
-    void equally_spaced_points(double distance, Points* points) const;
+    Polyline split_at_vertex(const Point &point) const;
+    Polyline split_at_index(int index) const;
+    Polyline split_at_first_point() const;
+    Points equally_spaced_points(double distance) const;
     double area() const;
     bool is_counter_clockwise() const;
     bool is_clockwise() const;
@@ -41,10 +40,8 @@ class Polygon : public MultiPoint {
     void triangulate_convex(Polygons* polygons) const;
     Point centroid() const;
     std::string wkt() const;
-    void concave_points(double angle, Points* points) const;
-    void concave_points(Points* points) const;
-    void convex_points(double angle, Points* points) const;
-    void convex_points(Points* points) const;
+    Points concave_points(double angle = PI) const;
+    Points convex_points(double angle = PI) const;
     
     #ifdef SLIC3RXS
     void from_SV_check(SV* poly_sv);
diff --git a/xs/src/libslic3r/Polyline.cpp b/xs/src/libslic3r/Polyline.cpp
index f56dd03b9..710ca9bd1 100644
--- a/xs/src/libslic3r/Polyline.cpp
+++ b/xs/src/libslic3r/Polyline.cpp
@@ -98,10 +98,11 @@ Polyline::extend_start(double distance)
 
 /* this method returns a collection of points picked on the polygon contour
    so that they are evenly spaced according to the input distance */
-void
-Polyline::equally_spaced_points(double distance, Points* points) const
+Points
+Polyline::equally_spaced_points(double distance) const
 {
-    points->push_back(this->first_point());
+    Points points;
+    points.push_back(this->first_point());
     double len = 0;
     
     for (Points::const_iterator it = this->points.begin() + 1; it != this->points.end(); ++it) {
@@ -110,17 +111,18 @@ Polyline::equally_spaced_points(double distance, Points* points) const
         if (len < distance) continue;
         
         if (len == distance) {
-            points->push_back(*it);
+            points.push_back(*it);
             len = 0;
             continue;
         }
         
         double take = segment_length - (len - distance);  // how much we take of this segment
         Line segment(*(it-1), *it);
-        points->push_back(segment.point_at(take));
+        points.push_back(segment.point_at(take));
         it--;
         len = -take;
     }
+    return points;
 }
 
 void
diff --git a/xs/src/libslic3r/Polyline.hpp b/xs/src/libslic3r/Polyline.hpp
index 3fe89f26e..cf91b7184 100644
--- a/xs/src/libslic3r/Polyline.hpp
+++ b/xs/src/libslic3r/Polyline.hpp
@@ -22,7 +22,7 @@ class Polyline : public MultiPoint {
     void clip_start(double distance);
     void extend_end(double distance);
     void extend_start(double distance);
-    void equally_spaced_points(double distance, Points* points) const;
+    Points equally_spaced_points(double distance) const;
     void simplify(double tolerance);
     template <class T> void simplify_by_visibility(const T &area);
     void split_at(const Point &point, Polyline* p1, Polyline* p2) const;
diff --git a/xs/src/libslic3r/Print.cpp b/xs/src/libslic3r/Print.cpp
index 47faf2a13..1944f22d3 100644
--- a/xs/src/libslic3r/Print.cpp
+++ b/xs/src/libslic3r/Print.cpp
@@ -358,8 +358,7 @@ Print::add_model_object(ModelObject* model_object, int idx)
     // initialize print object and store it at the given position
     PrintObject* o;
     {
-        BoundingBoxf3 bb;
-        model_object->raw_bounding_box(&bb);
+        BoundingBoxf3 bb = model_object->raw_bounding_box();
         if (idx != -1) {
             // replacing existing object
             PrintObjectPtrs::iterator old_it = this->objects.begin() + idx;
@@ -569,14 +568,13 @@ Print::validate() const
                     Polygons mesh_convex_hulls;
                     for (size_t i = 0; i < this->regions.size(); ++i) {
                         for (std::vector<int>::const_iterator it = object->region_volumes[i].begin(); it != object->region_volumes[i].end(); ++it) {
-                            Polygon hull;
-                            object->model_object()->volumes[*it]->mesh.convex_hull(&hull);
+                            Polygon hull = object->model_object()->volumes[*it]->mesh.convex_hull();
                             mesh_convex_hulls.push_back(hull);
                         }
                     }
                 
                     // make a single convex hull for all of them
-                    Slic3r::Geometry::convex_hull(mesh_convex_hulls, &convex_hull);
+                    convex_hull = Slic3r::Geometry::convex_hull(mesh_convex_hulls);
                 }
                 
                 // apply the same transformations we apply to the actual meshes when slicing them
diff --git a/xs/src/libslic3r/Print.hpp b/xs/src/libslic3r/Print.hpp
index 86964df48..dbc4ad1b8 100644
--- a/xs/src/libslic3r/Print.hpp
+++ b/xs/src/libslic3r/Print.hpp
@@ -111,7 +111,7 @@ class PrintObject
     bool delete_all_copies();
     bool set_copies(const Points &points);
     bool reload_model_instances();
-    void bounding_box(BoundingBox* bb) const;
+    BoundingBox bounding_box() const;
     
     // adds region_id, too, if necessary
     void add_region_volume(int region_id, int volume_id);
@@ -126,7 +126,7 @@ class PrintObject
     size_t support_layer_count() const;
     void clear_support_layers();
     SupportLayer* get_support_layer(int idx);
-    SupportLayer* add_support_layer(int id, coordf_t height, coordf_t print_z, coordf_t slice_z);
+    SupportLayer* add_support_layer(int id, coordf_t height, coordf_t print_z);
     void delete_support_layer(int idx);
     
     // methods for handling state
diff --git a/xs/src/libslic3r/PrintConfig.cpp b/xs/src/libslic3r/PrintConfig.cpp
index 81ed94f0b..a6e8b5fd5 100644
--- a/xs/src/libslic3r/PrintConfig.cpp
+++ b/xs/src/libslic3r/PrintConfig.cpp
@@ -22,6 +22,14 @@ PrintConfigDef::build_def() {
     Options["bed_temperature"].min = 0;
     Options["bed_temperature"].max = 300;
 
+    Options["before_layer_gcode"].type = coString;
+    Options["before_layer_gcode"].label = "Before layer change G-code";
+    Options["before_layer_gcode"].tooltip = "This custom code is inserted at every layer change, right before the Z move. Note that you can use placeholder variables for all Slic3r settings as well as [layer_num] and [layer_z].";
+    Options["before_layer_gcode"].cli = "before-layer-gcode=s";
+    Options["before_layer_gcode"].multiline = true;
+    Options["before_layer_gcode"].full_width = true;
+    Options["before_layer_gcode"].height = 50;
+
     Options["bottom_solid_layers"].type = coInt;
     Options["bottom_solid_layers"].label = "Bottom";
     Options["bottom_solid_layers"].category = "Layers and Perimeters";
@@ -119,7 +127,7 @@ PrintConfigDef::build_def() {
     Options["external_fill_pattern"].label = "Top/bottom fill pattern";
     Options["external_fill_pattern"].category = "Infill";
     Options["external_fill_pattern"].tooltip = "Fill pattern for top/bottom infill. This only affects the external visible layer, and not its adjacent solid shells.";
-    Options["external_fill_pattern"].cli = "external-fill-pattern=s";
+    Options["external_fill_pattern"].cli = "external-fill-pattern|solid-fill-pattern=s";
     Options["external_fill_pattern"].enum_keys_map = ConfigOptionEnum<InfillPattern>::get_enum_values();
     Options["external_fill_pattern"].enum_values.push_back("rectilinear");
     Options["external_fill_pattern"].enum_values.push_back("concentric");
@@ -318,7 +326,7 @@ PrintConfigDef::build_def() {
 
     Options["first_layer_extrusion_width"].type = coFloatOrPercent;
     Options["first_layer_extrusion_width"].label = "First layer";
-    Options["first_layer_extrusion_width"].tooltip = "Set this to a non-zero value to set a manual extrusion width for first layer. You can use this to force fatter extrudates for better adhesion. If expressed as percentage (for example 120%) it will be computed over first layer height.";
+    Options["first_layer_extrusion_width"].tooltip = "Set this to a non-zero value to set a manual extrusion width for first layer. You can use this to force fatter extrudates for better adhesion. If expressed as percentage (for example 120%) it will be computed over first layer height. If set to zero, it will use the Default Extrusion Width.";
     Options["first_layer_extrusion_width"].sidetext = "mm or % (leave 0 for default)";
     Options["first_layer_extrusion_width"].cli = "first-layer-extrusion-width=s";
     Options["first_layer_extrusion_width"].ratio_over = "first_layer_height";
@@ -421,6 +429,14 @@ PrintConfigDef::build_def() {
     Options["infill_only_where_needed"].tooltip = "This option will limit infill to the areas actually needed for supporting ceilings (it will act as internal support material).";
     Options["infill_only_where_needed"].cli = "infill-only-where-needed!";
 
+    Options["infill_overlap"].type = coFloatOrPercent;
+    Options["infill_overlap"].label = "Infill/perimeters overlap";
+    Options["infill_overlap"].category = "Advanced";
+    Options["infill_overlap"].tooltip = "This setting applies an additional overlap between infill and perimeters for better bonding. Theoretically this shouldn't be needed, but backlash might cause gaps. If expressed as percentage (example: 15%) it is calculated over perimeter extrusion width.";
+    Options["infill_overlap"].sidetext = "mm or %";
+    Options["infill_overlap"].cli = "infill-overlap=s";
+    Options["infill_overlap"].ratio_over = "perimeter_extrusion_width";
+
     Options["infill_speed"].type = coFloat;
     Options["infill_speed"].label = "Infill";
     Options["infill_speed"].category = "Speed";
@@ -438,9 +454,9 @@ PrintConfigDef::build_def() {
     Options["interface_shells"].category = "Layers and Perimeters";
 
     Options["layer_gcode"].type = coString;
-    Options["layer_gcode"].label = "Layer change G-code";
-    Options["layer_gcode"].tooltip = "This custom code is inserted at every layer change, right after the Z move and before the extruder moves to the first layer point. Note that you can use placeholder variables for all Slic3r settings.";
-    Options["layer_gcode"].cli = "layer-gcode=s";
+    Options["layer_gcode"].label = "After layer change G-code";
+    Options["layer_gcode"].tooltip = "This custom code is inserted at every layer change, right after the Z move and before the extruder moves to the first layer point. Note that you can use placeholder variables for all Slic3r settings as well as [layer_num] and [layer_z].";
+    Options["layer_gcode"].cli = "after-layer-gcode|layer-gcode=s";
     Options["layer_gcode"].multiline = true;
     Options["layer_gcode"].full_width = true;
     Options["layer_gcode"].height = 50;
@@ -799,6 +815,19 @@ PrintConfigDef::build_def() {
     Options["support_material_angle"].min = 0;
     Options["support_material_angle"].max = 359;
 
+    Options["support_material_contact_distance"].type = coFloat;
+    Options["support_material_contact_distance"].gui_type = "f_enum_open";
+    Options["support_material_contact_distance"].label = "Contact Z distance";
+    Options["support_material_contact_distance"].category = "Support material";
+    Options["support_material_contact_distance"].tooltip = "The vertical distance between object and support material interface. Setting this to 0 will also prevent Slic3r from using bridge flow and speed for the first object layer.";
+    Options["support_material_contact_distance"].sidetext = "mm";
+    Options["support_material_contact_distance"].cli = "support-material-contact-distance=f";
+    Options["support_material_contact_distance"].min = 0;
+    Options["support_material_contact_distance"].enum_values.push_back("0");
+    Options["support_material_contact_distance"].enum_values.push_back("0.2");
+    Options["support_material_contact_distance"].enum_labels.push_back("0 (soluble)");
+    Options["support_material_contact_distance"].enum_labels.push_back("0.2 (detachable)");
+
     Options["support_material_enforce_layers"].type = coInt;
     Options["support_material_enforce_layers"].label = "Enforce support for the first";
     Options["support_material_enforce_layers"].category = "Support material";
@@ -966,7 +995,7 @@ PrintConfigDef::build_def() {
 
     Options["use_volumetric_e"].type = coBool;
     Options["use_volumetric_e"].label = "Use volumetric E";
-    Options["use_volumetric_e"].tooltip = "This experimental setting uses outputs the E values in cubic millimeters instead of linear millimeters. The M200 command is prepended to the generated G-code, unless it is found in the configured start G-code. This is only supported in recent Marlin.";
+    Options["use_volumetric_e"].tooltip = "This experimental setting uses outputs the E values in cubic millimeters instead of linear millimeters. If your firmware doesn't already know filament diameter(s), you can put commands like 'M200 D[filament_diameter_0] T0' in your start G-code in order to turn volumetric mode on and use the filament diameter associated to the filament selected in Slic3r. This is only supported in recent Marlin.";
     Options["use_volumetric_e"].cli = "use-volumetric-e!";
 
     Options["vibration_limit"].type = coFloat;
diff --git a/xs/src/libslic3r/PrintConfig.hpp b/xs/src/libslic3r/PrintConfig.hpp
index 4f7160b82..caf52803e 100644
--- a/xs/src/libslic3r/PrintConfig.hpp
+++ b/xs/src/libslic3r/PrintConfig.hpp
@@ -133,6 +133,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
     ConfigOptionEnum<SeamPosition>  seam_position;
     ConfigOptionBool                support_material;
     ConfigOptionInt                 support_material_angle;
+    ConfigOptionFloat               support_material_contact_distance;
     ConfigOptionInt                 support_material_enforce_layers;
     ConfigOptionInt                 support_material_extruder;
     ConfigOptionFloatOrPercent      support_material_extrusion_width;
@@ -159,6 +160,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
         this->seam_position.value                                = spAligned;
         this->support_material.value                             = false;
         this->support_material_angle.value                       = 0;
+        this->support_material_contact_distance.value            = 0.2;
         this->support_material_enforce_layers.value              = 0;
         this->support_material_extruder.value                    = 1;
         this->support_material_extrusion_width.value             = 0;
@@ -186,6 +188,7 @@ class PrintObjectConfig : public virtual StaticPrintConfig
         if (opt_key == "seam_position")                              return &this->seam_position;
         if (opt_key == "support_material")                           return &this->support_material;
         if (opt_key == "support_material_angle")                     return &this->support_material_angle;
+        if (opt_key == "support_material_contact_distance")          return &this->support_material_contact_distance;
         if (opt_key == "support_material_enforce_layers")            return &this->support_material_enforce_layers;
         if (opt_key == "support_material_extruder")                  return &this->support_material_extruder;
         if (opt_key == "support_material_extrusion_width")           return &this->support_material_extrusion_width;
@@ -221,6 +224,7 @@ class PrintRegionConfig : public virtual StaticPrintConfig
     ConfigOptionInt                 infill_extruder;
     ConfigOptionFloatOrPercent      infill_extrusion_width;
     ConfigOptionInt                 infill_every_layers;
+    ConfigOptionFloatOrPercent      infill_overlap;
     ConfigOptionFloat               infill_speed;
     ConfigOptionBool                overhangs;
     ConfigOptionInt                 perimeter_extruder;
@@ -245,38 +249,40 @@ class PrintRegionConfig : public virtual StaticPrintConfig
         this->external_fill_pattern.value                        = ipRectilinear;
         this->external_perimeter_extrusion_width.value           = 0;
         this->external_perimeter_extrusion_width.percent         = false;
-        this->external_perimeter_speed.value                     = 70;
+        this->external_perimeter_speed.value                     = 50;
         this->external_perimeter_speed.percent                   = true;
         this->external_perimeters_first.value                    = false;
         this->extra_perimeters.value                             = true;
         this->fill_angle.value                                   = 45;
-        this->fill_density.value                                 = 40;
+        this->fill_density.value                                 = 20;
         this->fill_pattern.value                                 = ipHoneycomb;
         this->gap_fill_speed.value                               = 20;
         this->infill_extruder.value                              = 1;
         this->infill_extrusion_width.value                       = 0;
         this->infill_extrusion_width.percent                     = false;
         this->infill_every_layers.value                          = 1;
-        this->infill_speed.value                                 = 60;
+        this->infill_overlap.value                               = 15;
+        this->infill_overlap.percent                             = true;
+        this->infill_speed.value                                 = 80;
         this->overhangs.value                                    = true;
         this->perimeter_extruder.value                           = 1;
         this->perimeter_extrusion_width.value                    = 0;
         this->perimeter_extrusion_width.percent                  = false;
-        this->perimeter_speed.value                              = 30;
+        this->perimeter_speed.value                              = 60;
         this->perimeters.value                                   = 3;
         this->solid_infill_extruder.value                        = 1;
-        this->small_perimeter_speed.value                        = 30;
+        this->small_perimeter_speed.value                        = 15;
         this->small_perimeter_speed.percent                      = false;
         this->solid_infill_below_area.value                      = 70;
         this->solid_infill_extrusion_width.value                 = 0;
         this->solid_infill_extrusion_width.percent               = false;
         this->solid_infill_every_layers.value                    = 0;
-        this->solid_infill_speed.value                           = 60;
+        this->solid_infill_speed.value                           = 20;
         this->solid_infill_speed.percent                         = false;
         this->thin_walls.value                                   = true;
         this->top_infill_extrusion_width.value                   = 0;
         this->top_infill_extrusion_width.percent                 = false;
-        this->top_solid_infill_speed.value                       = 50;
+        this->top_solid_infill_speed.value                       = 15;
         this->top_solid_infill_speed.percent                     = false;
         this->top_solid_layers.value                             = 3;
     };
@@ -297,6 +303,7 @@ class PrintRegionConfig : public virtual StaticPrintConfig
         if (opt_key == "infill_extruder")                            return &this->infill_extruder;
         if (opt_key == "infill_extrusion_width")                     return &this->infill_extrusion_width;
         if (opt_key == "infill_every_layers")                        return &this->infill_every_layers;
+        if (opt_key == "infill_overlap")                             return &this->infill_overlap;
         if (opt_key == "infill_speed")                               return &this->infill_speed;
         if (opt_key == "overhangs")                                  return &this->overhangs;
         if (opt_key == "perimeter_extruder")                         return &this->perimeter_extruder;
@@ -321,6 +328,7 @@ class PrintRegionConfig : public virtual StaticPrintConfig
 class GCodeConfig : public virtual StaticPrintConfig
 {
     public:
+    ConfigOptionString              before_layer_gcode;
     ConfigOptionString              end_gcode;
     ConfigOptionString              extrusion_axis;
     ConfigOptionFloats              extrusion_multiplier;
@@ -343,6 +351,7 @@ class GCodeConfig : public virtual StaticPrintConfig
     ConfigOptionBool                use_volumetric_e;
     
     GCodeConfig() : StaticPrintConfig() {
+        this->before_layer_gcode.value                           = "";
         this->end_gcode.value                                    = "M104 S0 ; turn off temperature\nG28 X0  ; home X axis\nM84     ; disable motors\n";
         this->extrusion_axis.value                               = "E";
         this->extrusion_multiplier.values.resize(1);
@@ -354,7 +363,7 @@ class GCodeConfig : public virtual StaticPrintConfig
         this->layer_gcode.value                                  = "";
         this->pressure_advance.value                             = 0;
         this->retract_length.values.resize(1);
-        this->retract_length.values[0]                           = 1;
+        this->retract_length.values[0]                           = 2;
         this->retract_length_toolchange.values.resize(1);
         this->retract_length_toolchange.values[0]                = 10;
         this->retract_lift.values.resize(1);
@@ -364,7 +373,7 @@ class GCodeConfig : public virtual StaticPrintConfig
         this->retract_restart_extra_toolchange.values.resize(1);
         this->retract_restart_extra_toolchange.values[0]         = 0;
         this->retract_speed.values.resize(1);
-        this->retract_speed.values[0]                            = 30;
+        this->retract_speed.values[0]                            = 40;
         this->start_gcode.value                                  = "G28 ; home all axes\nG1 Z5 F5000 ; lift nozzle\n";
         this->toolchange_gcode.value                             = "";
         this->travel_speed.value                                 = 130;
@@ -374,6 +383,7 @@ class GCodeConfig : public virtual StaticPrintConfig
     };
     
     ConfigOption* option(const t_config_option_key opt_key, bool create = false) {
+        if (opt_key == "before_layer_gcode")                         return &this->before_layer_gcode;
         if (opt_key == "end_gcode")                                  return &this->end_gcode;
         if (opt_key == "extrusion_axis")                             return &this->extrusion_axis;
         if (opt_key == "extrusion_multiplier")                       return &this->extrusion_multiplier;
@@ -476,7 +486,7 @@ class PrintConfig : public GCodeConfig
         this->complete_objects.value                             = false;
         this->cooling.value                                      = true;
         this->default_acceleration.value                         = 0;
-        this->disable_fan_first_layers.value                     = 1;
+        this->disable_fan_first_layers.value                     = 3;
         this->duplicate_distance.value                           = 6;
         this->extruder_clearance_height.value                    = 20;
         this->extruder_clearance_radius.value                    = 20;
@@ -489,7 +499,7 @@ class PrintConfig : public GCodeConfig
         this->first_layer_extrusion_width.value                  = 200;
         this->first_layer_extrusion_width.percent                = true;
         this->first_layer_speed.value                            = 30;
-        this->first_layer_speed.percent                          = true;
+        this->first_layer_speed.percent                          = false;
         this->first_layer_temperature.values.resize(1);
         this->first_layer_temperature.values[0]                  = 200;
         this->gcode_arcs.value                                   = false;
@@ -510,11 +520,11 @@ class PrintConfig : public GCodeConfig
         this->retract_before_travel.values.resize(1);
         this->retract_before_travel.values[0]                    = 2;
         this->retract_layer_change.values.resize(1);
-        this->retract_layer_change.values[0]                     = true;
+        this->retract_layer_change.values[0]                     = false;
         this->skirt_distance.value                               = 6;
         this->skirt_height.value                                 = 1;
         this->skirts.value                                       = 1;
-        this->slowdown_below_layer_time.value                    = 30;
+        this->slowdown_below_layer_time.value                    = 5;
         this->spiral_vase.value                                  = false;
         this->standby_temperature_delta.value                    = -5;
         this->temperature.values.resize(1);
diff --git a/xs/src/libslic3r/PrintObject.cpp b/xs/src/libslic3r/PrintObject.cpp
index 1d33fbc00..fdf3116b7 100644
--- a/xs/src/libslic3r/PrintObject.cpp
+++ b/xs/src/libslic3r/PrintObject.cpp
@@ -110,14 +110,14 @@ PrintObject::reload_model_instances()
     return this->set_copies(copies);
 }
 
-void
-PrintObject::bounding_box(BoundingBox* bb) const
+BoundingBox
+PrintObject::bounding_box() const
 {
     // since the object is aligned to origin, bounding box coincides with size
     Points pp;
     pp.push_back(Point(0,0));
     pp.push_back(this->size);
-    *bb = BoundingBox(pp);
+    return BoundingBox(pp);
 }
 
 void
@@ -190,10 +190,9 @@ PrintObject::get_support_layer(int idx)
 }
 
 SupportLayer*
-PrintObject::add_support_layer(int id, coordf_t height, coordf_t print_z,
-    coordf_t slice_z)
+PrintObject::add_support_layer(int id, coordf_t height, coordf_t print_z)
 {
-    SupportLayer* layer = new SupportLayer(id, this, height, print_z, slice_z);
+    SupportLayer* layer = new SupportLayer(id, this, height, print_z, -1);
     support_layers.push_back(layer);
     return layer;
 }
@@ -219,6 +218,7 @@ PrintObject::invalidate_state_by_config_options(const std::vector<t_config_optio
             || *opt_key == "overhangs"
             || *opt_key == "first_layer_extrusion_width"
             || *opt_key == "perimeter_extrusion_width"
+            || *opt_key == "infill_overlap"
             || *opt_key == "thin_walls"
             || *opt_key == "external_perimeters_first") {
             steps.insert(posPerimeters);
diff --git a/xs/src/libslic3r/SVG.cpp b/xs/src/libslic3r/SVG.cpp
index 328d5421a..f196d4713 100644
--- a/xs/src/libslic3r/SVG.cpp
+++ b/xs/src/libslic3r/SVG.cpp
@@ -32,9 +32,17 @@ SVG::draw(const Line &line, std::string stroke)
 }
 
 void
-SVG::AddLine(const IntersectionLine &line)
+SVG::draw(const Lines &lines, std::string stroke)
 {
-    this->draw(Line(line.a, line.b));
+    for (Lines::const_iterator it = lines.begin(); it != lines.end(); ++it)
+        this->draw(*it, stroke);
+}
+
+void
+SVG::draw(const IntersectionLines &lines, std::string stroke)
+{
+    for (IntersectionLines::const_iterator it = lines.begin(); it != lines.end(); ++it)
+        this->draw((Line)*it, stroke);
 }
 
 void
@@ -50,11 +58,25 @@ SVG::draw(const ExPolygon &expolygon, std::string fill)
     this->path(d, true);
 }
 
+void
+SVG::draw(const ExPolygons &expolygons, std::string fill)
+{
+    for (ExPolygons::const_iterator it = expolygons.begin(); it != expolygons.end(); ++it)
+        this->draw(*it, fill);
+}
+
 void
 SVG::draw(const Polygon &polygon, std::string fill)
 {
     this->fill = fill;
-    this->path(this->get_path_d(polygon, true), true);
+    this->path(this->get_path_d(polygon, true), !fill.empty());
+}
+
+void
+SVG::draw(const Polygons &polygons, std::string fill)
+{
+    for (Polygons::const_iterator it = polygons.begin(); it != polygons.end(); ++it)
+        this->draw(*it, fill);
 }
 
 void
@@ -64,6 +86,13 @@ SVG::draw(const Polyline &polyline, std::string stroke)
     this->path(this->get_path_d(polyline, false), false);
 }
 
+void
+SVG::draw(const Polylines &polylines, std::string stroke)
+{
+    for (Polylines::const_iterator it = polylines.begin(); it != polylines.end(); ++it)
+        this->draw(*it, fill);
+}
+
 void
 SVG::draw(const Point &point, std::string fill, unsigned int radius)
 {
@@ -75,6 +104,13 @@ SVG::draw(const Point &point, std::string fill, unsigned int radius)
     fprintf(this->f, "%s\n", svg.str().c_str());
 }
 
+void
+SVG::draw(const Points &points, std::string fill, unsigned int radius)
+{
+    for (Points::const_iterator it = points.begin(); it != points.end(); ++it)
+        this->draw(*it, fill, radius);
+}
+
 void
 SVG::path(const std::string &d, bool fill)
 {
diff --git a/xs/src/libslic3r/SVG.hpp b/xs/src/libslic3r/SVG.hpp
index bb0d5adcf..cbc546402 100644
--- a/xs/src/libslic3r/SVG.hpp
+++ b/xs/src/libslic3r/SVG.hpp
@@ -15,12 +15,17 @@ class SVG
     std::string fill, stroke;
     
     SVG(const char* filename);
-    void AddLine(const IntersectionLine &line);
     void draw(const Line &line, std::string stroke = "black");
+    void draw(const Lines &lines, std::string stroke = "black");
+    void draw(const IntersectionLines &lines, std::string stroke = "black");
     void draw(const ExPolygon &expolygon, std::string fill = "grey");
+    void draw(const ExPolygons &expolygons, std::string fill = "grey");
     void draw(const Polygon &polygon, std::string fill = "grey");
+    void draw(const Polygons &polygons, std::string fill = "grey");
     void draw(const Polyline &polyline, std::string stroke = "black");
+    void draw(const Polylines &polylines, std::string stroke = "black");
     void draw(const Point &point, std::string fill = "black", unsigned int radius = 3);
+    void draw(const Points &points, std::string fill = "black", unsigned int radius = 3);
     void Close();
     
     private:
diff --git a/xs/src/libslic3r/TriangleMesh.cpp b/xs/src/libslic3r/TriangleMesh.cpp
index 7c2a0a344..b25df7e0e 100644
--- a/xs/src/libslic3r/TriangleMesh.cpp
+++ b/xs/src/libslic3r/TriangleMesh.cpp
@@ -181,6 +181,7 @@ TriangleMesh::WriteOBJFile(char* output_file) {
 void TriangleMesh::scale(float factor)
 {
     stl_scale(&(this->stl), factor);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::scale(const Pointf3 &versor)
@@ -190,41 +191,49 @@ void TriangleMesh::scale(const Pointf3 &versor)
     fversor[1] = versor.y;
     fversor[2] = versor.z;
     stl_scale_versor(&this->stl, fversor);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::translate(float x, float y, float z)
 {
     stl_translate_relative(&(this->stl), x, y, z);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::rotate_x(float angle)
 {
     stl_rotate_x(&(this->stl), angle);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::rotate_y(float angle)
 {
     stl_rotate_y(&(this->stl), angle);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::rotate_z(float angle)
 {
     stl_rotate_z(&(this->stl), angle);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::flip_x()
 {
     stl_mirror_yz(&this->stl);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::flip_y()
 {
     stl_mirror_xz(&this->stl);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::flip_z()
 {
     stl_mirror_xy(&this->stl);
+    stl_invalidate_shared_vertices(&this->stl);
 }
 
 void TriangleMesh::align_to_origin()
@@ -319,8 +328,8 @@ TriangleMesh::merge(const TriangleMesh &mesh)
 }
 
 /* this will return scaled ExPolygons */
-void
-TriangleMesh::horizontal_projection(ExPolygons &retval) const
+ExPolygons
+TriangleMesh::horizontal_projection() const
 {
     Polygons pp;
     pp.reserve(this->stl.stats.number_of_facets);
@@ -337,11 +346,13 @@ TriangleMesh::horizontal_projection(ExPolygons &retval) const
     
     // the offset factor was tuned using groovemount.stl
     offset(pp, &pp, 0.01 / SCALING_FACTOR);
+    ExPolygons retval;
     union_(pp, &retval, true);
+    return retval;
 }
 
-void
-TriangleMesh::convex_hull(Polygon* hull)
+Polygon
+TriangleMesh::convex_hull()
 {
     this->require_shared_vertices();
     Points pp;
@@ -350,25 +361,19 @@ TriangleMesh::convex_hull(Polygon* hull)
         stl_vertex* v = &this->stl.v_shared[i];
         pp.push_back(Point(v->x / SCALING_FACTOR, v->y / SCALING_FACTOR));
     }
-    Slic3r::Geometry::convex_hull(pp, hull);
-}
-
-void
-TriangleMesh::bounding_box(BoundingBoxf3* bb) const
-{
-    bb->min.x = this->stl.stats.min.x;
-    bb->min.y = this->stl.stats.min.y;
-    bb->min.z = this->stl.stats.min.z;
-    bb->max.x = this->stl.stats.max.x;
-    bb->max.y = this->stl.stats.max.y;
-    bb->max.z = this->stl.stats.max.z;
+    return Slic3r::Geometry::convex_hull(pp);
 }
 
 BoundingBoxf3
 TriangleMesh::bounding_box() const
 {
     BoundingBoxf3 bb;
-    this->bounding_box(&bb);
+    bb.min.x = this->stl.stats.min.x;
+    bb.min.y = this->stl.stats.min.y;
+    bb.min.z = this->stl.stats.min.z;
+    bb.max.x = this->stl.stats.max.x;
+    bb.max.y = this->stl.stats.max.y;
+    bb.max.z = this->stl.stats.max.z;
     return bb;
 }
 
@@ -511,7 +516,7 @@ TriangleMeshSlicer::slice(const std::vector<float> &z, std::vector<ExPolygons>*
     for (std::vector<Polygons>::const_iterator loops = layers_p.begin(); loops != layers_p.end(); ++loops) {
         #ifdef SLIC3R_DEBUG
         size_t layer_id = loops - layers_p.begin();
-        printf("Layer %zu (slice_z = %.2f): ", layer_id, z[layer_id]);
+        printf("Layer %zu (slice_z = %.2f):\n", layer_id, z[layer_id]);
         #endif
         
         this->make_expolygons(*loops, &(*layers)[ loops - layers_p.begin() ]);
@@ -546,15 +551,19 @@ TriangleMeshSlicer::slice_facet(float slice_z, const stl_facet &facet, const int
         if (a->z == b->z && a->z == slice_z) {
             // edge is horizontal and belongs to the current layer
             
-            /* We assume that this method is never being called for horizontal
-               facets, so no other edge is going to be on this layer. */
-            stl_vertex* v0 = &this->v_scaled_shared[ this->mesh->stl.v_indices[facet_idx].vertex[0] ];
-            stl_vertex* v1 = &this->v_scaled_shared[ this->mesh->stl.v_indices[facet_idx].vertex[1] ];
-            stl_vertex* v2 = &this->v_scaled_shared[ this->mesh->stl.v_indices[facet_idx].vertex[2] ];
+            stl_vertex &v0 = this->v_scaled_shared[ this->mesh->stl.v_indices[facet_idx].vertex[0] ];
+            stl_vertex &v1 = this->v_scaled_shared[ this->mesh->stl.v_indices[facet_idx].vertex[1] ];
+            stl_vertex &v2 = this->v_scaled_shared[ this->mesh->stl.v_indices[facet_idx].vertex[2] ];
             IntersectionLine line;
             if (min_z == max_z) {
                 line.edge_type = feHorizontal;
-            } else if (v0->z < slice_z || v1->z < slice_z || v2->z < slice_z) {
+                if (this->mesh->stl.facet_start[facet_idx].normal.z < 0) {
+                    /*  if normal points downwards this is a bottom horizontal facet so we reverse
+                        its point order */
+                    std::swap(a, b);
+                    std::swap(a_id, b_id);
+                }
+            } else if (v0.z < slice_z || v1.z < slice_z || v2.z < slice_z) {
                 line.edge_type = feTop;
                 std::swap(a, b);
                 std::swap(a_id, b_id);
@@ -628,12 +637,9 @@ TriangleMeshSlicer::slice_facet(float slice_z, const stl_facet &facet, const int
 void
 TriangleMeshSlicer::make_loops(std::vector<IntersectionLine> &lines, Polygons* loops)
 {
-        
     /*
     SVG svg("lines.svg");
-    for (IntersectionLines::iterator line = lines.begin(); line != lines.end(); ++line) {
-            svg.AddLine(*line);
-    }
+    svg.draw(lines);
     svg.Close();
     */
     
@@ -704,16 +710,16 @@ TriangleMeshSlicer::make_loops(std::vector<IntersectionLine> &lines, Polygons* l
             // find a line starting where last one finishes
             IntersectionLine* next_line = NULL;
             if (loop.back()->edge_b_id != -1) {
-                IntersectionLinePtrs* candidates = &(by_edge_a_id[loop.back()->edge_b_id]);
-                for (IntersectionLinePtrs::iterator lineptr = candidates->begin(); lineptr != candidates->end(); ++lineptr) {
+                IntersectionLinePtrs &candidates = by_edge_a_id[loop.back()->edge_b_id];
+                for (IntersectionLinePtrs::iterator lineptr = candidates.begin(); lineptr != candidates.end(); ++lineptr) {
                     if ((*lineptr)->skip) continue;
                     next_line = *lineptr;
                     break;
                 }
             }
             if (next_line == NULL && loop.back()->b_id != -1) {
-                IntersectionLinePtrs* candidates = &(by_a_id[loop.back()->b_id]);
-                for (IntersectionLinePtrs::iterator lineptr = candidates->begin(); lineptr != candidates->end(); ++lineptr) {
+                IntersectionLinePtrs &candidates = by_a_id[loop.back()->b_id];
+                for (IntersectionLinePtrs::iterator lineptr = candidates.begin(); lineptr != candidates.end(); ++lineptr) {
                     if ((*lineptr)->skip) continue;
                     next_line = *lineptr;
                     break;
@@ -841,9 +847,9 @@ TriangleMeshSlicer::make_expolygons(const Polygons &loops, ExPolygons* slices)
            of the loops, since the Orientation() function provided by Clipper
            would do the same, thus repeating the calculation */
         Polygons::const_iterator loop = loops.begin() + *loop_idx;
-        if (area[*loop_idx] >= 0) {
+        if (area[*loop_idx] > +EPSILON) {
             p_slices.push_back(*loop);
-        } else {
+        } else if (area[*loop_idx] < -EPSILON) {
             diff(p_slices, *loop, &p_slices);
         }
     }
diff --git a/xs/src/libslic3r/TriangleMesh.hpp b/xs/src/libslic3r/TriangleMesh.hpp
index 227bceae0..43ac68419 100644
--- a/xs/src/libslic3r/TriangleMesh.hpp
+++ b/xs/src/libslic3r/TriangleMesh.hpp
@@ -42,9 +42,8 @@ class TriangleMesh
     void rotate(double angle, Point* center);
     TriangleMeshPtrs split() const;
     void merge(const TriangleMesh &mesh);
-    void horizontal_projection(ExPolygons &retval) const;
-    void convex_hull(Polygon* hull);
-    void bounding_box(BoundingBoxf3* bb) const;
+    ExPolygons horizontal_projection() const;
+    Polygon convex_hull();
     BoundingBoxf3 bounding_box() const;
     void reset_repair_stats();
     bool needed_repair() const;
diff --git a/xs/src/libslic3r/libslic3r.h b/xs/src/libslic3r/libslic3r.h
index f700fd35a..8cdd13e26 100644
--- a/xs/src/libslic3r/libslic3r.h
+++ b/xs/src/libslic3r/libslic3r.h
@@ -6,7 +6,7 @@
 #include <iostream>
 #include <sstream>
 
-#define SLIC3R_VERSION "1.2.5-dev"
+#define SLIC3R_VERSION "1.2.6-dev"
 
 #define EPSILON 1e-4
 #define SCALING_FACTOR 0.000001
diff --git a/xs/t/01_trianglemesh.t b/xs/t/01_trianglemesh.t
index b2f1d2849..cc140aa5a 100644
--- a/xs/t/01_trianglemesh.t
+++ b/xs/t/01_trianglemesh.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 46;
+use Test::More tests => 49;
 
 is Slic3r::TriangleMesh::hello_world(), 'Hello world!',
     'hello world';
@@ -79,7 +79,7 @@ my $cube = {
     my $m = Slic3r::TriangleMesh->new;
     $m->ReadFromPerl($cube->{vertices}, $cube->{facets});
     $m->repair;
-    my @z = (2,4,8,6,8,10,12,14,16,18,20);
+    my @z = (0,2,4,8,6,8,10,12,14,16,18,20);
     my $result = $m->slice(\@z);
     my $SCALING_FACTOR = 0.000001;
     for my $i (0..$#z) {
@@ -95,8 +95,19 @@ my $cube = {
         [ [0,1,2],[2,1,3],[1,0,4],[5,1,4],[0,2,4],[4,2,6],[7,6,8],[4,6,7],[9,4,7],[7,8,10],[2,3,6],[11,3,12],[7,12,9],[13,12,7],[6,3,11],[11,12,13],[3,1,5],[12,3,5],[5,4,9],[12,5,9],[13,7,10],[14,13,10],[8,15,10],[10,15,14],[6,11,8],[8,11,15],[15,11,13],[14,15,13] ],
     );
     $m->repair;
-    my $slices = $m->slice([ 5, 10 ]);
-    is $slices->[0][0]->area, $slices->[1][0]->area, 'slicing a tangent plane includes its area';
+    {
+        # at Z = 10 we have a top horizontal surface
+        my $slices = $m->slice([ 5, 10 ]);
+        is $slices->[0][0]->area, $slices->[1][0]->area, 'slicing a top tangent plane includes its area';
+    }
+    $m->flip_z;
+    {
+        # this second test also checks that performing a second slice on a mesh after
+        # a transformation works properly (shared_vertices is correctly invalidated);
+        # at Z = -10 we have a bottom horizontal surface
+        my $slices = $m->slice([ -5, -10 ]);
+        is $slices->[0][0]->area, $slices->[1][0]->area, 'slicing a bottom tangent plane includes its area';
+    }
 }
 
 {
diff --git a/xs/t/10_line.t b/xs/t/10_line.t
index 67c3cd353..8f82e988c 100644
--- a/xs/t/10_line.t
+++ b/xs/t/10_line.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 39;
+use Test::More tests => 40;
 
 use constant PI         => 4 * atan2(1, 1);
 use constant EPSILON    => 1E-4;
@@ -71,4 +71,11 @@ foreach my $base_angle (0, PI/4, PI/2, PI) {
     }
 }
 
+{
+    my $a = Slic3r::Line->new([100, 0], [200, 0]);
+    my $b = Slic3r::Line->new([300, 300], [300, 100]);
+    my $r = $a->intersection_infinite($b);
+    is_deeply $r->pp, [300, 0], 'intersection_infinite';
+}
+
 __END__
diff --git a/xs/t/11_clipper.t b/xs/t/11_clipper.t
index efa051fe7..5c5b66349 100644
--- a/xs/t/11_clipper.t
+++ b/xs/t/11_clipper.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 18;
+use Test::More tests => 19;
 
 my $square = Slic3r::Polygon->new(  # ccw
     [200, 100],
@@ -155,8 +155,8 @@ if (0) {  # Clipper does not preserve polyline orientation
     }
 }
 
-# Disabled until Clipper bug #96 (our issue #2028) is fixed
-if (0) {
+{
+    # Clipper bug #96 (our issue #2028)
     my $subject = Slic3r::Polyline->new(
         [44735000,31936670],[55270000,31936670],[55270000,25270000],[74730000,25270000],[74730000,44730000],[68063296,44730000],[68063296,55270000],[74730000,55270000],[74730000,74730000],[55270000,74730000],[55270000,68063296],[44730000,68063296],[44730000,74730000],[25270000,74730000],[25270000,55270000],[31936670,55270000],[31936670,44730000],[25270000,44730000],[25270000,25270000],[44730000,25270000],[44730000,31936670]
     );
@@ -178,4 +178,19 @@ if (0) {
     is scalar(@$result), 1, 'intersection_ppl - result is not empty';
 }
 
+if (0) {
+    # Disabled until Clipper bug #122 is fixed
+    my $subject = [
+        Slic3r::Polyline->new([1975,1975],[25,1975],[25,25],[1975,25],[1975,1975]),
+    ];
+    my $clip = [
+        Slic3r::Polygon->new([2025,2025],[-25,2025],[-25,-25],[2025,-25]),
+        Slic3r::Polygon->new([525,525],[525,1475],[1475,1475],[1475,525]),
+    ];
+    my $result = Slic3r::Geometry::Clipper::intersection_pl($subject, $clip);
+    ###use XXX; YYY $subject->[0]->wkt, [map $_->wkt, @$clip], $result->[0]->wkt;
+    is scalar(@$result), 1, 'intersection_pl - result is not empty';
+    is scalar(@{$result->[0]}), 5, 'intersection_pl - result is not empty';
+}
+
 __END__
diff --git a/xs/xsp/BoundingBox.xsp b/xs/xsp/BoundingBox.xsp
index eafe55766..22eb0ea7d 100644
--- a/xs/xsp/BoundingBox.xsp
+++ b/xs/xsp/BoundingBox.xsp
@@ -16,8 +16,7 @@
     void scale(double factor);
     void translate(double x, double y);
     void offset(double delta);
-    Polygon* polygon()
-        %code{% RETVAL = new Polygon(); THIS->polygon(RETVAL); %};
+    Clone<Polygon> polygon();
     Clone<Point> size();
     Clone<Point> center();
     Clone<Point> min_point() %code{% RETVAL = THIS->min; %};
@@ -88,6 +87,8 @@ new_from_points(CLASS, points)
     void translate(double x, double y, double z);
     Clone<Pointf3> size();
     Clone<Pointf3> center();
+    Clone<Pointf3> min_point() %code{% RETVAL = THIS->min; %};
+    Clone<Pointf3> max_point() %code{% RETVAL = THIS->max; %};
     double x_min() %code{% RETVAL = THIS->min.x; %};
     double x_max() %code{% RETVAL = THIS->max.x; %};
     double y_min() %code{% RETVAL = THIS->min.y; %};
diff --git a/xs/xsp/ExPolygonCollection.xsp b/xs/xsp/ExPolygonCollection.xsp
index 4ae1a9156..99ef69608 100644
--- a/xs/xsp/ExPolygonCollection.xsp
+++ b/xs/xsp/ExPolygonCollection.xsp
@@ -26,6 +26,7 @@
     void simplify(double tolerance);
     Polygons polygons()
         %code{% RETVAL = *THIS; %};
+    Clone<Polygon> convex_hull();
 %{
 
 ExPolygonCollection*
@@ -76,13 +77,5 @@ ExPolygonCollection::append(...)
             THIS->expolygons.push_back(expolygon);
         }
 
-Polygon*
-ExPolygonCollection::convex_hull()
-    CODE:
-        RETVAL = new Polygon ();
-        THIS->convex_hull(RETVAL);
-    OUTPUT:
-        RETVAL
-
 %}
 };
diff --git a/xs/xsp/ExtrusionEntityCollection.xsp b/xs/xsp/ExtrusionEntityCollection.xsp
index fa1d26eed..a7c5a8be0 100644
--- a/xs/xsp/ExtrusionEntityCollection.xsp
+++ b/xs/xsp/ExtrusionEntityCollection.xsp
@@ -24,8 +24,11 @@
     Clone<Point> last_point();
     int count()
         %code{% RETVAL = THIS->entities.size(); %};
+    bool empty()
+        %code{% RETVAL = THIS->entities.empty(); %};
     std::vector<size_t> orig_indices()
         %code{% RETVAL = THIS->orig_indices; %};
+    Polygons grow();
 %{
 
 void
diff --git a/xs/xsp/ExtrusionLoop.xsp b/xs/xsp/ExtrusionLoop.xsp
index 2a8d1f9f4..0da0fe0d4 100644
--- a/xs/xsp/ExtrusionLoop.xsp
+++ b/xs/xsp/ExtrusionLoop.xsp
@@ -15,8 +15,7 @@
     bool make_counter_clockwise();
     Clone<Point> first_point();
     Clone<Point> last_point();
-    Polygon* polygon()
-        %code{% RETVAL = new Polygon (*THIS); %};
+    Clone<Polygon> polygon();
     void append(ExtrusionPath* path)
         %code{% THIS->paths.push_back(*path); %};
     double length();
@@ -31,6 +30,7 @@
     bool is_perimeter();
     bool is_infill();
     bool is_solid_infill();
+    Polygons grow();
 %{
 
 SV*
diff --git a/xs/xsp/ExtrusionPath.xsp b/xs/xsp/ExtrusionPath.xsp
index 4fbaea2d6..57fee2b61 100644
--- a/xs/xsp/ExtrusionPath.xsp
+++ b/xs/xsp/ExtrusionPath.xsp
@@ -29,6 +29,7 @@
     std::string gcode(Extruder* extruder, double e, double F,
         double xofs, double yofs, std::string extrusion_axis,
         std::string gcode_line_suffix);
+    Polygons grow();
 %{
 
 ExtrusionPath*
diff --git a/xs/xsp/GUI_3DScene.xsp b/xs/xsp/GUI_3DScene.xsp
new file mode 100644
index 000000000..7e692326d
--- /dev/null
+++ b/xs/xsp/GUI_3DScene.xsp
@@ -0,0 +1,28 @@
+%module{Slic3r::XS};
+
+#include <myinit.h>
+#include "libslic3r/GUI/3DScene.hpp"
+
+%name{Slic3r::GUI::_3DScene::GLVertexArray} class GLVertexArray {
+    GLVertexArray();
+    ~GLVertexArray();
+    void load_mesh(TriangleMesh* mesh) const
+        %code%{ THIS->load_mesh(*mesh); %};
+    size_t size() const
+        %code%{ RETVAL = THIS->verts.size(); %};
+    void* verts_ptr() const
+        %code%{ RETVAL = THIS->verts.empty() ? 0 : &THIS->verts.front(); %};
+    void* norms_ptr() const
+        %code%{ RETVAL = THIS->verts.empty() ? 0 : &THIS->norms.front(); %};
+};
+
+%package{Slic3r::GUI::_3DScene};
+%{
+
+void
+_extrusionentity_to_verts_do(Lines lines, std::vector<double> widths, std::vector<double> heights, bool closed, double top_z, Point* copy, GLVertexArray* qverts, GLVertexArray* tverts)
+    CODE:
+        _3DScene::_extrusionentity_to_verts_do(lines, widths, heights, closed,
+            top_z, *copy, qverts, tverts);
+
+%}
\ No newline at end of file
diff --git a/xs/xsp/Geometry.xsp b/xs/xsp/Geometry.xsp
index 8a587415c..0df74a4bd 100644
--- a/xs/xsp/Geometry.xsp
+++ b/xs/xsp/Geometry.xsp
@@ -29,12 +29,11 @@ directions_parallel_within(angle1, angle2, max_diff)
     OUTPUT:
         RETVAL
 
-Polygon*
+Clone<Polygon>
 convex_hull(points)
     Points      points
     CODE:
-        RETVAL = new Polygon ();
-        Slic3r::Geometry::convex_hull(points, RETVAL);
+        RETVAL = Slic3r::Geometry::convex_hull(points);
     OUTPUT:
         RETVAL
 
@@ -79,4 +78,13 @@ deg2rad(angle)
     OUTPUT:
         RETVAL
 
+Polygons
+simplify_polygons(polygons, tolerance)
+    Polygons    polygons
+    double      tolerance
+    CODE:
+        Slic3r::Geometry::simplify_polygons(polygons, tolerance, &RETVAL);
+    OUTPUT:
+        RETVAL
+
 %}
diff --git a/xs/xsp/Layer.xsp b/xs/xsp/Layer.xsp
index ffc9f9af8..611e2cae9 100644
--- a/xs/xsp/Layer.xsp
+++ b/xs/xsp/Layer.xsp
@@ -26,15 +26,17 @@
     Ref<ExtrusionEntityCollection> fills()
         %code%{ RETVAL = &THIS->fills; %};
     
-    Flow* flow(FlowRole role, bool bridge = false, double width = -1)
-        %code%{ RETVAL = new Flow(THIS->flow(role, bridge, width)); %};
+    Clone<Flow> flow(FlowRole role, bool bridge = false, double width = -1)
+        %code%{ RETVAL = THIS->flow(role, bridge, width); %};
     void merge_slices();
+    void prepare_fill_surfaces();
 };
 
 %name{Slic3r::Layer} class Layer {
     // owned by PrintObject, no constructor/destructor
 
     int id();
+    void set_id(int id);
     Ref<PrintObject> object();
     Ref<Layer> upper_layer()
         %code%{ RETVAL = THIS->upper_layer; %};
@@ -89,6 +91,7 @@
     // copies of some Layer methods, because the parameter wrapper code
     // gets confused about getting a Layer::Support instead of a Layer
     int id();
+    void set_id(int id);
     Ref<PrintObject> object();
     Ref<SupportLayer> upper_layer()
         %code%{ RETVAL = (SupportLayer*)THIS->upper_layer; %};
diff --git a/xs/xsp/Line.xsp b/xs/xsp/Line.xsp
index 69d9fbce1..7ee644494 100644
--- a/xs/xsp/Line.xsp
+++ b/xs/xsp/Line.xsp
@@ -28,11 +28,19 @@
     bool parallel_to(double angle);
     bool parallel_to_line(Line* line)
         %code{% RETVAL = THIS->parallel_to(*line); %};
-    Point* midpoint();
+    Clone<Point> midpoint();
     Clone<Point> point_at(double distance);
-    Polyline* as_polyline()
-        %code{% RETVAL = new Polyline(*THIS); %};
+    Clone<Point> intersection_infinite(Line* other)
+        %code{%
+            Point p;
+            bool res = THIS->intersection_infinite(*other, &p);
+            if (!res) CONFESS("Intersection failed");
+            RETVAL = p;
+        %};
+    Clone<Polyline> as_polyline()
+        %code{% RETVAL = Polyline(*THIS); %};
     Clone<Point> normal();
+    Clone<Point> vector();
 %{
 
 Line*
@@ -79,4 +87,5 @@ Line::coincides_with(line_sv)
     Ref<Pointf3> b()
         %code{% RETVAL = &THIS->b; %};
     Clone<Pointf3> intersect_plane(double z);
+    void scale(double factor);
 };
diff --git a/xs/xsp/Model.xsp b/xs/xsp/Model.xsp
index 2252d357d..9870d7dd5 100644
--- a/xs/xsp/Model.xsp
+++ b/xs/xsp/Model.xsp
@@ -59,19 +59,13 @@
     // void duplicate(size_t copies_num, coordf_t distance, const BoundingBox &bb);
     bool has_objects_with_no_instances();
     bool add_default_instances();
-    BoundingBoxf3* bounding_box()
-        %code%{
-            RETVAL = new BoundingBoxf3();
-            THIS->bounding_box(RETVAL);
-        %};
+    Clone<BoundingBoxf3> bounding_box();
     void center_instances_around_point(Pointf* point)
         %code%{ THIS->center_instances_around_point(*point); %};
     void align_instances_to_origin();
     void translate(double x, double y, double z);
-    TriangleMesh* mesh()
-        %code%{ RETVAL = new TriangleMesh(); THIS->mesh(RETVAL); %};
-    TriangleMesh* raw_mesh()
-        %code%{ RETVAL = new TriangleMesh(); THIS->raw_mesh(RETVAL); %};
+    Clone<TriangleMesh> mesh();
+    Clone<TriangleMesh> raw_mesh();
     // void split_meshes();
     // std::string get_material_name(t_model_material_id material_id);
 
@@ -119,20 +113,10 @@ ModelMaterial::attributes()
     
     void invalidate_bounding_box();
     void update_bounding_box();
-    TriangleMesh* mesh()
-        %code%{ RETVAL = new TriangleMesh(); THIS->mesh(RETVAL); %};
-    TriangleMesh* raw_mesh()
-        %code%{ RETVAL = new TriangleMesh(); THIS->raw_mesh(RETVAL); %};
-    BoundingBoxf3* raw_bounding_box()
-        %code%{
-            RETVAL = new BoundingBoxf3();
-            THIS->raw_bounding_box(RETVAL);
-        %};
-    BoundingBoxf3* instance_bounding_box(int idx)
-        %code%{
-            RETVAL = new BoundingBoxf3();
-            THIS->instance_bounding_box(idx, RETVAL);
-        %};
+    Clone<TriangleMesh> mesh();
+    Clone<TriangleMesh> raw_mesh();
+    Clone<BoundingBoxf3> raw_bounding_box();
+    Clone<BoundingBoxf3> instance_bounding_box(int idx);
 
     Ref<BoundingBoxf3> _bounding_box(BoundingBoxf3* new_bbox = NULL)
         %code{%
@@ -147,11 +131,7 @@ ModelMaterial::attributes()
 
             RETVAL = &THIS->_bounding_box;
         %};
-    BoundingBoxf3* bounding_box()
-        %code%{
-            RETVAL = new BoundingBoxf3();
-            THIS->bounding_box(RETVAL);
-        %};
+    Clone<BoundingBoxf3> bounding_box();
 
     %name{_add_volume} Ref<ModelVolume> add_volume(TriangleMesh* mesh)
         %code%{ RETVAL = THIS->add_volume(*mesh); %};
diff --git a/xs/xsp/MotionPlanner.xsp b/xs/xsp/MotionPlanner.xsp
index fc4bae715..896923307 100644
--- a/xs/xsp/MotionPlanner.xsp
+++ b/xs/xsp/MotionPlanner.xsp
@@ -10,6 +10,6 @@
     ~MotionPlanner();
     
     int islands_count();
-    Polyline* shortest_path(Point* from, Point* to)
-        %code%{ RETVAL = new Polyline(); THIS->shortest_path(*from, *to, RETVAL); %};
+    Clone<Polyline> shortest_path(Point* from, Point* to)
+        %code%{ RETVAL = THIS->shortest_path(*from, *to); %};
 };
diff --git a/xs/xsp/Point.xsp b/xs/xsp/Point.xsp
index 871911239..34017a3b4 100644
--- a/xs/xsp/Point.xsp
+++ b/xs/xsp/Point.xsp
@@ -22,9 +22,13 @@
         %code{% RETVAL = THIS->x; %};
     long y()
         %code{% RETVAL = THIS->y; %};
+    void set_x(long val)
+        %code{% THIS->x = val; %};
+    void set_y(long val)
+        %code{% THIS->y = val; %};
     int nearest_point_index(Points points);
-    Point* nearest_point(Points points)
-        %code{% RETVAL = new Point(); THIS->nearest_point(points, RETVAL); %};
+    Clone<Point> nearest_point(Points points)
+        %code{% Point p; THIS->nearest_point(points, &p); RETVAL = p; %};
     double distance_to(Point* point)
         %code{% RETVAL = THIS->distance_to(*point); %};
     double distance_to_line(Line* line)
diff --git a/xs/xsp/Polygon.xsp b/xs/xsp/Polygon.xsp
index 6a8eac99c..824a65310 100644
--- a/xs/xsp/Polygon.xsp
+++ b/xs/xsp/Polygon.xsp
@@ -19,14 +19,11 @@
     void translate(double x, double y);
     void reverse();
     Lines lines();
-    Polyline* split_at_vertex(Point* point)
-        %code{% RETVAL = new Polyline(); THIS->split_at_vertex(*point, RETVAL); %};
-    Polyline* split_at_index(int index)
-        %code{% RETVAL = new Polyline(); THIS->split_at_index(index, RETVAL); %};
-    Polyline* split_at_first_point()
-        %code{% RETVAL = new Polyline(); THIS->split_at_first_point(RETVAL); %};
-    Points equally_spaced_points(double distance)
-        %code{% THIS->equally_spaced_points(distance, &RETVAL); %};
+    Clone<Polyline> split_at_vertex(Point* point)
+        %code{% RETVAL = THIS->split_at_vertex(*point); %};
+    Clone<Polyline> split_at_index(int index);
+    Clone<Polyline> split_at_first_point();
+    Points equally_spaced_points(double distance);
     double length();
     double area();
     bool is_counter_clockwise();
@@ -41,16 +38,10 @@
     Polygons triangulate_convex()
         %code{% THIS->triangulate_convex(&RETVAL); %};
     Clone<Point> centroid();
-    BoundingBox* bounding_box()
-        %code{%
-            RETVAL = new BoundingBox();
-            THIS->bounding_box(RETVAL);
-        %};
+    Clone<BoundingBox> bounding_box();
     std::string wkt();
-    Points concave_points(double angle)
-        %code{% THIS->concave_points(angle, &RETVAL); %};
-    Points convex_points(double angle)
-        %code{% THIS->convex_points(angle, &RETVAL); %};
+    Points concave_points(double angle);
+    Points convex_points(double angle);
 %{
 
 Polygon*
diff --git a/xs/xsp/Polyline.xsp b/xs/xsp/Polyline.xsp
index a8eb527d5..98cd44e94 100644
--- a/xs/xsp/Polyline.xsp
+++ b/xs/xsp/Polyline.xsp
@@ -23,8 +23,7 @@
     Lines lines();
     Clone<Point> first_point();
     Clone<Point> last_point();
-    Points equally_spaced_points(double distance)
-        %code{% THIS->equally_spaced_points(distance, &RETVAL); %};
+    Points equally_spaced_points(double distance);
     double length();
     bool is_valid();
     void clip_end(double distance);
@@ -37,11 +36,8 @@
     void split_at(Point* point, Polyline* p1, Polyline* p2)
         %code{% THIS->split_at(*point, p1, p2); %};
     bool is_straight();
-    BoundingBox* bounding_box()
-        %code{%
-            RETVAL = new BoundingBox();
-            THIS->bounding_box(RETVAL);
-        %};
+    Clone<BoundingBox> bounding_box();
+    void remove_duplicate_points();
     std::string wkt();
 %{
 
diff --git a/xs/xsp/Print.xsp b/xs/xsp/Print.xsp
index 94237da05..13ce4f1c3 100644
--- a/xs/xsp/Print.xsp
+++ b/xs/xsp/Print.xsp
@@ -35,8 +35,8 @@ _constant()
         %code%{ RETVAL = &THIS->config; %};
     Ref<Print> print();
     
-    Flow* flow(FlowRole role, double layer_height, bool bridge, bool first_layer, double width, PrintObject* object)
-        %code%{ RETVAL = new Flow(THIS->flow(role, layer_height, bridge, first_layer, width, *object)); %};
+    Clone<Flow> flow(FlowRole role, double layer_height, bool bridge, bool first_layer, double width, PrintObject* object)
+        %code%{ RETVAL = THIS->flow(role, layer_height, bridge, first_layer, width, *object); %};
 };
 
 
@@ -61,11 +61,7 @@ _constant()
         %code%{ RETVAL = THIS->layer_height_ranges; %};
     Ref<Point3> size()
         %code%{ RETVAL = &THIS->size; %};
-    BoundingBox* bounding_box()
-        %code{%
-            RETVAL = new BoundingBox();
-            THIS->bounding_box(RETVAL);
-        %};
+    Clone<BoundingBox> bounding_box();
     Ref<Point> _copies_shift()
         %code%{ RETVAL = &THIS->_copies_shift; %};
     
@@ -99,7 +95,7 @@ _constant()
     size_t support_layer_count();
     void clear_support_layers();
     Ref<SupportLayer> get_support_layer(int idx);
-    Ref<SupportLayer> add_support_layer(int id, coordf_t height, coordf_t print_z, coordf_t slice_z);
+    Ref<SupportLayer> add_support_layer(int id, coordf_t height, coordf_t print_z);
     void delete_support_layer(int idx);
     
     bool invalidate_state_by_config_options(std::vector<std::string> opt_keys);
diff --git a/xs/xsp/TriangleMesh.xsp b/xs/xsp/TriangleMesh.xsp
index 122a84f48..d87030693 100644
--- a/xs/xsp/TriangleMesh.xsp
+++ b/xs/xsp/TriangleMesh.xsp
@@ -31,19 +31,11 @@
     TriangleMeshPtrs split();
     void merge(TriangleMesh* mesh)
         %code{% THIS->merge(*mesh); %};
-    ExPolygons horizontal_projection()
-        %code{% THIS->horizontal_projection(RETVAL); %};
-    BoundingBoxf3* bounding_box()
-        %code{%
-            RETVAL = new BoundingBoxf3();
-            THIS->bounding_box(RETVAL);
-        %};
-    Pointf3* center()
-        %code{%
-            BoundingBoxf3 bb;
-            THIS->bounding_box(&bb);
-            RETVAL = new Pointf3(bb.center());
-        %};
+    ExPolygons horizontal_projection();
+    Clone<Polygon> convex_hull();
+    Clone<BoundingBoxf3> bounding_box();
+    Clone<Pointf3> center()
+        %code{% RETVAL = THIS->bounding_box().center(); %};
     int facets_count();
     void reset_repair_stats();
 %{
@@ -196,14 +188,6 @@ TriangleMesh::bb3()
     OUTPUT:
         RETVAL
 
-Polygon*
-TriangleMesh::convex_hull()
-    CODE:
-        RETVAL = new Polygon ();
-        THIS->convex_hull(RETVAL);
-    OUTPUT:
-        RETVAL
-
 %}
 };
 
diff --git a/xs/xsp/my.map b/xs/xsp/my.map
index 4391c3bfc..bf5828004 100644
--- a/xs/xsp/my.map
+++ b/xs/xsp/my.map
@@ -186,6 +186,8 @@ BridgeDetector*            O_OBJECT_SLIC3R
 Ref<BridgeDetector>        O_OBJECT_SLIC3R_T
 Clone<BridgeDetector>      O_OBJECT_SLIC3R_T
 
+GLVertexArray*             O_OBJECT_SLIC3R
+
 ExtrusionLoopRole     T_UV
 ExtrusionRole     T_UV
 FlowRole     T_UV
@@ -329,13 +331,11 @@ T_ARRAYREF
     if (SvROK($arg) && SvTYPE(SvRV($arg)) == SVt_PVAV) {
         AV* av = (AV*)SvRV($arg);
         const unsigned int len = av_len(av)+1;
-        $type* tmp = new $type(len);
+        $var.resize(len);
         for (unsigned int i = 0; i < len; i++) {
             SV** elem = av_fetch(av, i, 0);
-            (*tmp)[i].from_SV_check(*elem);
+            $var\[i].from_SV_check(*elem);
         }
-        $var = *tmp;
-	    delete tmp;
     } else
         Perl_croak(aTHX_ \"%s: %s is not an array reference\",
 	             ${$ALIAS?\q[GvNAME(CvGV(cv))]:\qq[\"$pname\"]},
@@ -396,6 +396,7 @@ T_STD_STRING
 T_STD_VECTOR_STD_STRING
 	AV* av = newAV();
 	$arg = newRV_noinc((SV*)av);
+	sv_2mortal($arg);
 	const unsigned int len = $var.size();
         if (len)
           av_extend(av, len-1);
@@ -408,6 +409,7 @@ T_STD_VECTOR_STD_STRING
 T_STD_VECTOR_INT
 	AV* av = newAV();
 	$arg = newRV_noinc((SV*)av);
+	sv_2mortal($arg);
 	const unsigned int len = $var.size();
         if (len)
           av_extend(av, len-1);
@@ -418,6 +420,7 @@ T_STD_VECTOR_INT
 T_STD_VECTOR_UINT
 	AV* av = newAV();
 	$arg = newRV_noinc((SV*)av);
+	sv_2mortal($arg);
 	const unsigned int len = $var.size();
         if (len)
           av_extend(av, len-1);
@@ -428,6 +431,7 @@ T_STD_VECTOR_UINT
 T_STD_VECTOR_DOUBLE
 	AV* av = newAV();
 	$arg = newRV_noinc((SV*)av);
+	sv_2mortal($arg);
 	const unsigned int len = $var.size();
         if (len)
           av_extend(av, len-1);
@@ -458,7 +462,6 @@ T_ARRAYREF
     for (${type}::const_iterator it = $var.begin(); it != $var.end(); ++it) {
         av_store(av, i++, perl_to_SV_clone_ref(*it));
 	}
-	$var.clear();
 
 T_ARRAYREF_PTR
     AV* av = newAV();
diff --git a/xs/xsp/typemap.xspt b/xs/xsp/typemap.xspt
index 00d3c08d9..845b98707 100644
--- a/xs/xsp/typemap.xspt
+++ b/xs/xsp/typemap.xspt
@@ -13,6 +13,7 @@
 %typemap{std::vector<unsigned int>*};
 %typemap{std::vector<std::string>};
 %typemap{t_layer_height_ranges};
+%typemap{void*};
 %typemap{SV*};
 %typemap{AV*};
 %typemap{Point*};
@@ -167,6 +168,7 @@
 %typemap{ModelInstancePtrs*};
 %typemap{Ref<ModelInstancePtrs>}{simple};
 %typemap{Clone<ModelInstancePtrs>}{simple};
+%typemap{GLVertexArray*};
 
 %typemap{PrintRegionPtrs*};
 %typemap{PrintObjectPtrs*};