diff --git a/lib/Slic3r/ExPolygon.pm b/lib/Slic3r/ExPolygon.pm
index 8330bb7f2..1d1793a71 100644
--- a/lib/Slic3r/ExPolygon.pm
+++ b/lib/Slic3r/ExPolygon.pm
@@ -298,7 +298,7 @@ sub medial_axis {
 }
 
 package Slic3r::ExPolygon::XS;
-use base 'Slic3r::ExPolygon';
+use parent 'Slic3r::ExPolygon';
 
 package Slic3r::ExPolygon::Collection;
 use Slic3r::Geometry qw(X1 Y1);
diff --git a/lib/Slic3r/ExtrusionPath.pm b/lib/Slic3r/ExtrusionPath.pm
index 3409a5975..2234aa9e2 100644
--- a/lib/Slic3r/ExtrusionPath.pm
+++ b/lib/Slic3r/ExtrusionPath.pm
@@ -1,8 +1,10 @@
 package Slic3r::ExtrusionPath;
-use Moo;
+use strict;
+use warnings;
+
+use parent -norequire, qw(Slic3r::Polyline::XS);
+use parent qw(Exporter);
 
-require Exporter;
-our @ISA = qw(Exporter);
 our @EXPORT_OK = qw(EXTR_ROLE_PERIMETER EXTR_ROLE_EXTERNAL_PERIMETER 
     EXTR_ROLE_CONTOUR_INTERNAL_PERIMETER EXTR_ROLE_OVERHANG_PERIMETER
     EXTR_ROLE_FILL EXTR_ROLE_SOLIDFILL EXTR_ROLE_TOPSOLIDFILL EXTR_ROLE_BRIDGE 
@@ -10,67 +12,22 @@ our @EXPORT_OK = qw(EXTR_ROLE_PERIMETER EXTR_ROLE_EXTERNAL_PERIMETER
 our %EXPORT_TAGS = (roles => \@EXPORT_OK);
 
 use Slic3r::Geometry qw(PI X Y epsilon deg2rad rotate_points);
-
-# the underlying Slic3r::Polyline objects holds the geometry
-has 'polyline' => (
-    is          => 'rw',
-    required    => 1,
-    handles     => [qw(merge_continuous_lines lines length reverse clip_end)],
-);
-
-# height is the vertical thickness of the extrusion expressed in mm
-has 'height'       => (is => 'rw');
-has 'flow_spacing' => (is => 'rw', required => 1);
-has 'role'         => (is => 'rw', required => 1);
-
-use constant EXTR_ROLE_PERIMETER                    => 0;
-use constant EXTR_ROLE_EXTERNAL_PERIMETER           => 1;
-use constant EXTR_ROLE_OVERHANG_PERIMETER           => 2;
-use constant EXTR_ROLE_CONTOUR_INTERNAL_PERIMETER   => 3;
-use constant EXTR_ROLE_FILL                         => 4;
-use constant EXTR_ROLE_SOLIDFILL                    => 5;
-use constant EXTR_ROLE_TOPSOLIDFILL                 => 6;
-use constant EXTR_ROLE_BRIDGE                       => 7;
-use constant EXTR_ROLE_INTERNALBRIDGE               => 8;
-use constant EXTR_ROLE_SKIRT                        => 9;
-use constant EXTR_ROLE_SUPPORTMATERIAL              => 10;
-use constant EXTR_ROLE_GAPFILL                      => 11;
-
-use constant PACK_FMT => 'ffca*';
+sub polyline { $_[0] }
 
 # class or object method
 sub pack {
     my $self = shift;
-    my %args = @_;
     
     if (ref $self) {
-        %args = map { $_ => $self->$_ } qw(height flow_spacing role polyline);
+        return $self;
+    } else {
+        return $self->new(@_);
     }
-    
-    my $o = \ pack PACK_FMT,
-        $args{height}       // -1,
-        $args{flow_spacing} || -1,
-        $args{role}         // (die "Missing mandatory attribute 'role'"), #/
-        $args{polyline}->serialize;
-    
-    bless $o, 'Slic3r::ExtrusionPath::Packed';
-    return $o;
 }
 
 # no-op, this allows to use both packed and non-packed objects in Collections
 sub unpack { $_[0] }
 
-sub clone {
-    my $self = shift;
-    my %p = @_;
-    
-    $p{polyline} ||= $self->polyline->clone;
-    return (ref $self)->new(
-        (map { $_ => $self->$_ } qw(polyline height flow_spacing role)),
-        %p,
-    );
-}
-
 sub clip_with_polygon {
     my $self = shift;
     my ($polygon) = @_;
@@ -91,7 +48,7 @@ sub intersect_expolygons {
     my ($expolygons) = @_;
     
     return map $self->clone(polyline => Slic3r::Polyline->new(@$_)),
-        @{Boost::Geometry::Utils::multi_polygon_multi_linestring_intersection($expolygons, [$self->polyline])};
+        @{Boost::Geometry::Utils::multi_polygon_multi_linestring_intersection($expolygons, [$self->arrayref])};
 }
 
 sub subtract_expolygons {
@@ -99,12 +56,12 @@ sub subtract_expolygons {
     my ($expolygons) = @_;
     
     return map $self->clone(polyline => Slic3r::Polyline->new(@$_)),
-        @{Boost::Geometry::Utils::multi_linestring_multi_polygon_difference([$self->polyline], $expolygons)};
+        @{Boost::Geometry::Utils::multi_linestring_multi_polygon_difference([$self->arrayref], $expolygons)};
 }
 
 sub simplify {
     my $self = shift;
-    $self->polyline($self->polyline->simplify(@_));
+    $self->set_polyline($self->as_polyline->simplify(@_));
 }
 
 sub points {
@@ -285,19 +242,4 @@ sub detect_arcs {
     return @paths;
 }
 
-package Slic3r::ExtrusionPath::Packed;
-sub unpack {
-    my $self = shift;
-    
-    my ($height, $flow_spacing, $role, $polyline_s)
-        = unpack Slic3r::ExtrusionPath::PACK_FMT, $$self;
-    
-    return Slic3r::ExtrusionPath->new(
-        height          => ($height == -1) ? undef : $height,
-        flow_spacing    => ($flow_spacing == -1) ? undef : $flow_spacing,
-        role            => $role,
-        polyline        => Slic3r::Polyline->deserialize($polyline_s),
-    );
-}
-
 1;
diff --git a/lib/Slic3r/Fill.pm b/lib/Slic3r/Fill.pm
index d88def835..1efe8163d 100644
--- a/lib/Slic3r/Fill.pm
+++ b/lib/Slic3r/Fill.pm
@@ -185,7 +185,7 @@ sub make_fill {
                         : $is_bridge
                             ? EXTR_ROLE_BRIDGE
                             : $is_solid
-                                ? ($surface->surface_type == S_TYPE_TOP ? EXTR_ROLE_TOPSOLIDFILL : EXTR_ROLE_SOLIDFILL)
+                                ? (($surface->surface_type == S_TYPE_TOP) ? EXTR_ROLE_TOPSOLIDFILL : EXTR_ROLE_SOLIDFILL)
                                 : EXTR_ROLE_FILL),
                     height => $surface->thickness,
                     flow_spacing => $params->{flow_spacing} || (warn "Warning: no flow_spacing was returned by the infill engine, please report this to the developer\n"),
diff --git a/lib/Slic3r/Fill/Base.pm b/lib/Slic3r/Fill/Base.pm
index f1e530ecb..d0c9d4f30 100644
--- a/lib/Slic3r/Fill/Base.pm
+++ b/lib/Slic3r/Fill/Base.pm
@@ -27,7 +27,7 @@ sub infill_direction {
     }
         
     # use bridge angle
-    if (defined $surface->bridge_angle) {
+    if ($surface->bridge_angle != -1) {
         Slic3r::debugf "Filling bridge with angle %d\n", $surface->bridge_angle;
         $rotate[0] = Slic3r::Geometry::deg2rad($surface->bridge_angle);
     }
diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index 1807f84ee..a657dc011 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -256,7 +256,6 @@ sub extrude_path {
     my $self = shift;
     my ($path, $description, %params) = @_;
     
-    $path = $path->unpack if $path->isa('Slic3r::ExtrusionPath::Packed');
     $path->simplify(&Slic3r::SCALED_RESOLUTION);
     
     # detect arcs
@@ -293,7 +292,7 @@ sub extrude_path {
         $area = ($s**2) * PI/4;
     } else {
         my $s = $path->flow_spacing;
-        my $h = $path->height // $self->layer->height;
+        my $h = (defined $path->height && $path->height != -1) ? $path->height : $self->layer->height;
         $area = $self->extruder->mm3_per_mm($s, $h);
     }
     
diff --git a/lib/Slic3r/Geometry.pm b/lib/Slic3r/Geometry.pm
index 337b0b564..b082dc7b5 100644
--- a/lib/Slic3r/Geometry.pm
+++ b/lib/Slic3r/Geometry.pm
@@ -228,8 +228,9 @@ sub point_is_on_left_of_segment {
 }
 
 sub polyline_lines {
-    my ($polygon) = @_;
-    return map Slic3r::Line->new($polygon->[$_], $polygon->[$_+1]), 0 .. $#$polygon-1;
+    my ($polyline) = @_;
+    my @points = @$polyline;
+    return map Slic3r::Line->new(@points[$_, $_+1]), 0 .. $#points-1;
 }
 
 sub polygon_lines {
diff --git a/lib/Slic3r/Layer/Region.pm b/lib/Slic3r/Layer/Region.pm
index 5771316c4..602475533 100644
--- a/lib/Slic3r/Layer/Region.pm
+++ b/lib/Slic3r/Layer/Region.pm
@@ -352,7 +352,7 @@ sub _fill_gaps {
             
             foreach my $expolygon (@infill) {
                 my @paths = $filler->fill_surface(
-                    Slic3r::Surface->new(expolygon => $expolygon),
+                    Slic3r::Surface->new(expolygon => $expolygon, surface_type => S_TYPE_INTERNALSOLID),
                     density         => 1,
                     flow_spacing    => $flow->spacing,
                 );
@@ -573,7 +573,7 @@ sub _detect_bridges {
         Slic3r::debugf "  Optimal infill angle of bridge on layer %d is %d degrees\n",
             $self->id, $bridge_angle if defined $bridge_angle;
         
-        $surface->bridge_angle($bridge_angle);
+        $surface->bridge_angle($bridge_angle // -1);
     }
 }
 
diff --git a/lib/Slic3r/Polygon.pm b/lib/Slic3r/Polygon.pm
index f743ac543..1025755b5 100644
--- a/lib/Slic3r/Polygon.pm
+++ b/lib/Slic3r/Polygon.pm
@@ -163,4 +163,7 @@ sub concave_points {
         -1 .. ($#$self-1);
 }
 
+package Slic3r::Polygon::XS;
+use parent -norequire, qw(Slic3r::Polygon Slic3r::Polyline::XS);
+
 1;
\ No newline at end of file
diff --git a/lib/Slic3r/Polyline.pm b/lib/Slic3r/Polyline.pm
index b979abad0..39a936372 100644
--- a/lib/Slic3r/Polyline.pm
+++ b/lib/Slic3r/Polyline.pm
@@ -22,6 +22,9 @@ sub clone {
     Storable::dclone($_[0])
 }
 
+# compability with ::XS
+sub arrayref { $_[0] }
+
 sub serialize {
     my $self = shift;
     return pack 'l*', map @$_, @$self;
@@ -59,7 +62,7 @@ sub simplify {
     my $self = shift;
     my $tolerance = shift || 10;
     
-    my $simplified = Boost::Geometry::Utils::linestring_simplify($self, $tolerance);
+    my $simplified = Boost::Geometry::Utils::linestring_simplify($self->arrayref, $tolerance);
     return (ref $self)->new(@$simplified);
 }
 
@@ -70,7 +73,7 @@ sub reverse {
 
 sub length {
     my $self = shift;
-    return Boost::Geometry::Utils::linestring_length($self);
+    return Boost::Geometry::Utils::linestring_length($self->arrayref);
 }
 
 sub grow {
@@ -161,14 +164,25 @@ sub scale {
     return $self;
 }
 
+sub pop_back {
+    my $self = shift;
+    return pop @$self;
+}
+
+sub append {
+    my $self = shift;
+    push @$self, @_;
+}
+
 # removes the given distance from the end of the polyline
 sub clip_end {
     my $self = shift;
     my ($distance) = @_;
     
     while ($distance > 0) {
-        my $last_point = pop @$self;
-        last if !@$self;
+        my $last_point = $self->[-1];
+        $self->pop_back;
+        last if @$self == 0;
         
         my $last_segment_length = $last_point->distance_to($self->[-1]);
         if ($last_segment_length <= $distance) {
@@ -177,7 +191,7 @@ sub clip_end {
         }
         
         my $new_point = Slic3r::Geometry::point_along_segment($last_point, $self->[-1], $distance);
-        push @$self, Slic3r::Point->new($new_point);
+        $self->append(Slic3r::Point->new($new_point));
         $distance = 0;
     }
 }
@@ -244,4 +258,7 @@ sub chained_path {
     return map $items_map{"$_"}, @paths;
 }
 
+package Slic3r::Polyline::XS;
+use parent qw(Slic3r::Polyline);
+
 1;
diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index 240c4d3dc..8e56673cd 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -589,14 +589,14 @@ sub discover_horizontal_shells {
                 # and the latter contains the enlarged external surfaces
                 my $solid = [ map $_->expolygon, grep $_->surface_type == $type, @{$layerm->slices}, @{$layerm->fill_surfaces} ];
                 next if !@$solid;
-                Slic3r::debugf "Layer %d has %s surfaces\n", $i, ($type == S_TYPE_TOP ? 'top' : 'bottom');
+                Slic3r::debugf "Layer %d has %s surfaces\n", $i, ($type == S_TYPE_TOP) ? 'top' : 'bottom';
                 
                 my $solid_layers = ($type == S_TYPE_TOP)
                     ? $Slic3r::Config->top_solid_layers
                     : $Slic3r::Config->bottom_solid_layers;
-                for (my $n = $type == S_TYPE_TOP ? $i-1 : $i+1; 
+                for (my $n = ($type == S_TYPE_TOP) ? $i-1 : $i+1; 
                         abs($n - $i) <= $solid_layers-1; 
-                        $type == S_TYPE_TOP ? $n-- : $n++) {
+                        ($type == S_TYPE_TOP) ? $n-- : $n++) {
                     
                     next if $n < 0 || $n >= $self->layer_count;
                     Slic3r::debugf "  looking for neighbors on layer %d...\n", $n;
@@ -607,7 +607,7 @@ sub discover_horizontal_shells {
                     # intersections have contours and holes
                     my $new_internal_solid = intersection_ex(
                         [ map @$_, @$solid ],
-                        [ map $_->p, grep { $_->surface_type == S_TYPE_INTERNAL || $_->surface_type == S_TYPE_INTERNALSOLID } @neighbor_fill_surfaces ],
+                        [ map $_->p, grep { ($_->surface_type == S_TYPE_INTERNAL) || ($_->surface_type == S_TYPE_INTERNALSOLID) } @neighbor_fill_surfaces ],
                         undef, 1,
                     );
                     next if !@$new_internal_solid;
@@ -658,25 +658,22 @@ sub discover_horizontal_shells {
                     
                     # assign resulting internal surfaces to layer
                     my $neighbor_fill_surfaces = $self->layers->[$n]->regions->[$region_id]->fill_surfaces;
-                    @$neighbor_fill_surfaces = ();
-                    push @$neighbor_fill_surfaces, Slic3r::Surface->new
-                        (expolygon => $_, surface_type => S_TYPE_INTERNAL)
-                        for @$internal;
+                    $neighbor_fill_surfaces->clear;
+                    $neighbor_fill_surfaces->append(map Slic3r::Surface->new
+                        (expolygon => $_, surface_type => S_TYPE_INTERNAL), @$internal);
                     
                     # assign new internal-solid surfaces to layer
-                    push @$neighbor_fill_surfaces, Slic3r::Surface->new
-                        (expolygon => $_, surface_type => S_TYPE_INTERNALSOLID)
-                        for @$internal_solid;
+                    $neighbor_fill_surfaces->append(map Slic3r::Surface->new
+                        (expolygon => $_, surface_type => S_TYPE_INTERNALSOLID), @$internal_solid);
                     
                     # assign top and bottom surfaces to layer
-                    foreach my $s (Slic3r::Surface->group(grep { $_->surface_type == S_TYPE_TOP || $_->surface_type == S_TYPE_BOTTOM } @neighbor_fill_surfaces)) {
+                    foreach my $s (Slic3r::Surface->group(grep { ($_->surface_type == S_TYPE_TOP) || ($_->surface_type == S_TYPE_BOTTOM) } @neighbor_fill_surfaces)) {
                         my $solid_surfaces = diff_ex(
                             [ map $_->p, @$s ],
                             [ map @$_, @$internal_solid, @$internal ],
                             1,
                         );
-                        push @$neighbor_fill_surfaces, $s->[0]->clone(expolygon => $_)
-                            for @$solid_surfaces;
+                        $neighbor_fill_surfaces->append(map $s->[0]->clone(expolygon => $_), @$solid_surfaces);
                     }
                 }
             }
diff --git a/t/fill.t b/t/fill.t
index 28c2509bd..58c539ba9 100644
--- a/t/fill.t
+++ b/t/fill.t
@@ -33,7 +33,7 @@ sub scale_points (@) { map [scale $_->[X], scale $_->[Y]], @_ }
 }
 
 {
-    my $expolygon = Slic3r::ExPolygon->new([ scale_points [0,0], [50,0], [50,50], [0,50] ]);
+    my $expolygon = Slic3r::ExPolygon::XS->new([ scale_points [0,0], [50,0], [50,50], [0,50] ]);
     my $filler = Slic3r::Fill::Rectilinear->new(
         bounding_box => $expolygon->bounding_box,
     );
diff --git a/t/freeze.t b/t/freeze.t
deleted file mode 100644
index 07fd020d2..000000000
--- a/t/freeze.t
+++ /dev/null
@@ -1,30 +0,0 @@
-use Test::More tests => 1;
-use strict;
-use warnings;
-
-BEGIN {
-    use FindBin;
-    use lib "$FindBin::Bin/../lib";
-}
-
-use Slic3r;
-use Slic3r::Test;
-use Storable qw(nstore retrieve);
-use Time::HiRes qw(gettimeofday tv_interval);
-
-{
-    my $t0 = [gettimeofday];
-    my $print = Slic3r::Test::init_print('20mm_cube', scale => 2);
-    my $gcode = Slic3r::Test::gcode($print);
-    ###diag sprintf 'Slicing took %s seconds', tv_interval($t0);
-    
-    my $t1 = [gettimeofday];
-    nstore $print, 'print.dat';
-    $print = retrieve 'print.dat';
-    unlink 'print.dat';
-    ###diag sprintf 'Freezing and retrieving took %s seconds', tv_interval($t1);
-    
-    isa_ok $print, 'Slic3r::Print', 'restored Print object';
-}
-
-__END__
diff --git a/t/shells.t b/t/shells.t
index 56a3ca595..7abca9b13 100644
--- a/t/shells.t
+++ b/t/shells.t
@@ -1,4 +1,4 @@
-use Test::More tests => 3;
+use Test::More tests => 4;
 use strict;
 use warnings;
 
@@ -15,6 +15,10 @@ use Slic3r::Test;
     my $config = Slic3r::Config->new_from_defaults;
     $config->set('skirts', 0);
     $config->set('perimeters', 0);
+    $config->set('solid_infill_speed', 99);
+    $config->set('top_solid_infill_speed', 99);
+    $config->set('first_layer_speed', '100%');
+    $config->set('cooling', 0);
     
     my $test = sub {
         my ($conf) = @_;
@@ -28,20 +32,31 @@ use Slic3r::Test;
             
             if ($self->Z > 0) {
                 $layers_with_shells{$self->Z} //= 0;
-                $layers_with_shells{$self->Z} = 1 if $info->{extruding} && $info->{dist_XY} > 0;
+                $layers_with_shells{$self->Z} = 1
+                    if $info->{extruding}
+                        && $info->{dist_XY} > 0
+                        && ($args->{F} // $self->F) == $config->solid_infill_speed*60;
             }
         });
         my @shells = @layers_with_shells{sort { $a <=> $b } keys %layers_with_shells};
-        fail "wrong number of bottom solid layers"
+        fail "insufficient number of bottom solid layers"
             unless !defined(first { !$_ } @shells[0..$config->bottom_solid_layers-1]);
-        fail "wrong number of top solid layers"
+        fail "excessive number of bottom solid layers"
+            unless scalar(grep $_, @shells[0 .. $#shells/2]) != $config->bottom_solid_layers;
+        fail "insufficient number of top solid layers"
             unless !defined(first { !$_ } @shells[-$config->top_solid_layers..-1]);
+        fail "excessive number of top solid layers"
+            unless scalar(grep $_, @shells[($#shells/2)..$#shells]) != $config->top_solid_layers;
         1;
     };
     
     ok $test->(), "proper number of shells is applied";
-    $config->set('fill_density', 0);
     
+    $config->set('top_solid_layers', 0);
+    $config->set('bottom_solid_layers', 0);
+    ok $test->(), "no shells are applied when both top and bottom are set to zero";
+    
+    $config->set('fill_density', 0);
     ok $test->(), "proper number of shells is applied even when fill density is none";
 }
 
@@ -55,6 +70,7 @@ use Slic3r::Test;
     $config->set('cooling', 0);
     $config->set('solid_infill_speed', 99);
     $config->set('top_solid_infill_speed', 99);
+    $config->set('first_layer_speed', '100%');
     
     my $print = Slic3r::Test::init_print('V', config => $config);
     my %layers_with_solid_infill = ();  # Z => 1
diff --git a/xs/lib/Slic3r/XS.pm b/xs/lib/Slic3r/XS.pm
index 1d1ef3eae..498c0df70 100644
--- a/xs/lib/Slic3r/XS.pm
+++ b/xs/lib/Slic3r/XS.pm
@@ -15,10 +15,78 @@ package Slic3r::ExPolygon::XS;
 use overload
     '@{}' => sub { $_[0]->arrayref };
 
+package Slic3r::Polyline::XS;
+use overload
+    '@{}' => sub { $_[0]->arrayref },
+    'fallback' => 1;
+
+package Slic3r::Polygon::XS;
+use overload
+    '@{}' => sub { $_[0]->arrayref };
+
 package Slic3r::ExPolygon::Collection;
 use overload
     '@{}' => sub { $_[0]->arrayref };
 
+package Slic3r::ExtrusionLoop;
+
+sub new {
+    my ($class, %args) = @_;
+    
+    my $polygon = ref($args{polygon}) eq 'Slic3r::Polygon::XS'
+        ? $args{polygon}
+        : Slic3r::Polygon::XS->new(@{$args{polygon}});
+    
+    return $class->_new(
+        $polygon,            # required
+        $args{role},         # required
+        $args{height}        // -1,
+        $args{flow_spacing}  // -1,
+    );
+}
+
+sub clone {
+    my ($self, %args) = @_;
+    
+    return (ref $self)->_new(
+        $args{polygon}       // $self->polygon->clone,
+        $args{role}          // $self->role,
+        $args{height}        // $self->height,
+        $args{flow_spacing}  // $self->flow_spacing,
+    );
+}
+
+package Slic3r::ExtrusionPath;
+use overload
+    '@{}' => sub { $_[0]->arrayref },
+    'fallback' => 1;
+
+sub new {
+    my ($class, %args) = @_;
+    
+    my $polyline = ref($args{polyline}) eq 'Slic3r::Polyline::XS'
+        ? $args{polyline}
+        : Slic3r::Polyline::XS->new(@{$args{polyline}});
+    
+    return $class->_new(
+        $polyline,                  # required
+        $args{role},         # required
+        $args{height}        // -1,
+        $args{flow_spacing}  // -1,
+    );
+}
+
+sub clone {
+    my ($self, %args) = @_;
+    
+    return (ref $self)->_new(
+        $args{polyline}      // $self->as_polyline,
+        $args{role}          // $self->role,
+        $args{height}        // $self->height,
+        $args{flow_spacing}  // $self->flow_spacing,
+    );
+}
+
 package Slic3r::Surface;
 
 sub new {
@@ -29,12 +97,12 @@ sub new {
         if defined $args{bridge_angle} && $args{bridge_angle} < 0;
     
     return $class->_new(
-        delete $args{expolygon},                # required
-        delete $args{surface_type},             # required
-        delete $args{thickness}         // -1,
-        delete $args{thickness_layers}  // 1,
-        delete $args{bridge_angle}      // -1,
-        delete $args{extra_perimeters}  // 0,
+        $args{expolygon}         // (die "Missing required expolygon\n"),
+        $args{surface_type}      // (die "Missing required surface_type\n"),
+        $args{thickness}         // -1,
+        $args{thickness_layers}  // 1,
+        $args{bridge_angle}      // -1,
+        $args{extra_perimeters}  // 0,
     );
 }
 
diff --git a/xs/src/ExtrusionEntity.hpp b/xs/src/ExtrusionEntity.hpp
new file mode 100644
index 000000000..257bd3ff2
--- /dev/null
+++ b/xs/src/ExtrusionEntity.hpp
@@ -0,0 +1,60 @@
+#ifndef slic3r_ExtrusionEntity_hpp_
+#define slic3r_ExtrusionEntity_hpp_
+
+extern "C" {
+#include "EXTERN.h"
+#include "perl.h"
+#include "XSUB.h"
+#include "ppport.h"
+}
+
+#include "Polygon.hpp"
+#include "Polyline.hpp"
+
+namespace Slic3r {
+
+enum ExtrusionRole {
+    erPerimeter,
+    erExternalPerimeter,
+    erOverhangPerimeter,
+    erContourInternalPerimeter,
+    erFill,
+    erSolidFill,
+    erTopSolidFill,
+    erBrige,
+    erInternalBridge,
+    erSkirt,
+    erSupportMaterial,
+    erGapFill,
+};
+
+class ExtrusionEntity
+{
+    public:
+    ExtrusionRole role;
+    double height;  // vertical thickness of the extrusion expressed in mm
+    double flow_spacing;
+};
+
+class ExtrusionPath : public ExtrusionEntity
+{
+    public:
+    Polyline polyline;
+    void reverse();
+};
+
+class ExtrusionLoop : public ExtrusionEntity
+{
+    public:
+    Polygon polygon;
+};
+
+void
+ExtrusionPath::reverse()
+{
+    this->polyline.reverse();
+}
+
+}
+
+#endif
diff --git a/xs/src/Polyline.hpp b/xs/src/Polyline.hpp
index 65285126d..0941314c1 100644
--- a/xs/src/Polyline.hpp
+++ b/xs/src/Polyline.hpp
@@ -9,6 +9,7 @@ extern "C" {
 }
 
 #include "Point.hpp"
+#include <algorithm>
 
 namespace Slic3r {
 
@@ -19,6 +20,7 @@ class Polyline
     void scale(double factor);
     void translate(double x, double y);
     void rotate(double angle, Point* center);
+    void reverse();
 };
 
 typedef std::vector<Polyline> Polylines;
@@ -49,6 +51,12 @@ Polyline::rotate(double angle, Point* center)
     }
 }
 
+void
+Polyline::reverse()
+{
+    std::reverse(this->points.begin(), this->points.end());
+}
+
 void
 perl2polyline(SV* poly_sv, Polyline& poly)
 {
diff --git a/xs/t/05_surface.t b/xs/t/05_surface.t
index a881c8198..94b308a83 100644
--- a/xs/t/05_surface.t
+++ b/xs/t/05_surface.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 
 use Slic3r::XS;
-use Test::More tests => 10;
+use Test::More tests => 11;
 
 my $square = [  # ccw
     [100, 100],
@@ -49,6 +49,10 @@ is $surface->extra_perimeters, 2, 'extra_perimeters';
     is scalar(@$collection), 0, 'clear collection';
     $collection->append($surface);
     is scalar(@$collection), 1, 'append to collection';
+    
+    my $item = $collection->[0];
+    $item->surface_type(Slic3r::Surface::S_TYPE_INTERNAL);
+    is $item->surface_type, $collection->[0]->surface_type, 'changing item affects actual item';
 }
 
 __END__
diff --git a/xs/t/06_polygon.t b/xs/t/06_polygon.t
new file mode 100644
index 000000000..cca7032b8
--- /dev/null
+++ b/xs/t/06_polygon.t
@@ -0,0 +1,22 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+use Slic3r::XS;
+use Test::More tests => 3;
+
+my $square = [  # ccw
+    [100, 100],
+    [200, 100],
+    [200, 200],
+    [100, 200],
+];
+
+my $polygon = Slic3r::Polygon::XS->new(@$square);
+is_deeply [ @$polygon ], [ @$square ], 'polygon roundtrip';
+
+isa_ok $polygon->arrayref, 'Slic3r::Polygon', 'Perl polygon is blessed';
+isa_ok $polygon->[0], 'Slic3r::Point', 'Perl points are blessed';
+
+__END__
diff --git a/xs/t/07_extrusionpath.t b/xs/t/07_extrusionpath.t
new file mode 100644
index 000000000..5a8d4c5c1
--- /dev/null
+++ b/xs/t/07_extrusionpath.t
@@ -0,0 +1,37 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+
+use Slic3r::XS;
+use Test::More tests => 7;
+
+my $points = [
+    [100, 100],
+    [200, 100],
+    [200, 200],
+];
+
+my $path = Slic3r::ExtrusionPath->new(
+    polyline => Slic3r::Polyline::XS->new(@$points),
+    role     => Slic3r::ExtrusionPath::EXTR_ROLE_EXTERNAL_PERIMETER,
+);
+isa_ok $path->as_polyline, 'Slic3r::Polyline::XS', 'path polyline';
+is_deeply [ @{ $path->as_polyline } ], [ @$points ], 'path points roundtrip';
+
+$path->reverse;
+is_deeply [ @{ $path->as_polyline } ], [ reverse @$points ], 'reverse path';
+
+$path->append([ 150, 150 ]);
+is scalar(@{ $path }), 4, 'append to path';
+
+$path->pop_back;
+is scalar(@{ $path }), 3, 'pop_back from path';
+
+$path = $path->clone;
+
+is $path->role, Slic3r::ExtrusionPath::EXTR_ROLE_EXTERNAL_PERIMETER, 'role';
+$path->role(Slic3r::ExtrusionPath::EXTR_ROLE_FILL);
+is $path->role, Slic3r::ExtrusionPath::EXTR_ROLE_FILL, 'modify role';
+
+__END__
diff --git a/xs/xsp/ExtrusionPath.xsp b/xs/xsp/ExtrusionPath.xsp
new file mode 100644
index 000000000..d27573d22
--- /dev/null
+++ b/xs/xsp/ExtrusionPath.xsp
@@ -0,0 +1,126 @@
+%module{Slic3r::XS};
+
+%{
+#include <myinit.h>
+#include "ExtrusionEntity.hpp"
+%}
+
+%name{Slic3r::ExtrusionPath} class ExtrusionPath {
+    ~ExtrusionPath();
+    SV* arrayref()
+        %code{% RETVAL = polyline2perl(THIS->polyline); %};
+    void pop_back()
+        %code{% THIS->polyline.points.pop_back(); %};
+    void reverse();
+%{
+
+ExtrusionPath*
+_new(CLASS, polyline_sv, role, height, flow_spacing)
+    char*           CLASS;
+    SV*             polyline_sv;
+    ExtrusionRole   role;
+    double          height;
+    double          flow_spacing;
+    CODE:
+        RETVAL = new ExtrusionPath ();
+        if (sv_isobject(polyline_sv) && (SvTYPE(SvRV(polyline_sv)) == SVt_PVMG)) {
+            RETVAL->polyline = *(Polyline*)SvIV((SV*)SvRV( polyline_sv ));
+        } else {
+            perl2polyline(polyline_sv, RETVAL->polyline);
+        }
+        RETVAL->role            = role;
+        RETVAL->height          = height;
+        RETVAL->flow_spacing    = flow_spacing;
+    OUTPUT:
+        RETVAL
+
+Polyline*
+ExtrusionPath::as_polyline()
+    PREINIT:
+        const char* CLASS = "Slic3r::Polyline::XS";
+    CODE:
+        RETVAL = new Polyline(THIS->polyline);
+    OUTPUT:
+        RETVAL
+
+void
+ExtrusionPath::set_polyline(polyline_sv)
+    SV* polyline_sv;
+    CODE:
+        if (sv_isobject(polyline_sv) && (SvTYPE(SvRV(polyline_sv)) == SVt_PVMG)) {
+            THIS->polyline = *(Polyline*)SvIV((SV*)SvRV( polyline_sv ));
+        } else {
+            perl2polyline(polyline_sv, THIS->polyline);
+        }
+
+ExtrusionRole
+ExtrusionPath::role(...)
+    CODE:
+        if (items > 1) {
+            THIS->role = (ExtrusionRole)SvUV(ST(1));
+        }
+        RETVAL = THIS->role;
+    OUTPUT:
+        RETVAL
+
+double
+ExtrusionPath::height(...)
+    CODE:
+        if (items > 1) {
+            THIS->height = (double)SvNV(ST(1));
+        }
+        RETVAL = THIS->height;
+    OUTPUT:
+        RETVAL
+
+double
+ExtrusionPath::flow_spacing(...)
+    CODE:
+        if (items > 1) {
+            THIS->flow_spacing = (double)SvNV(ST(1));
+        }
+        RETVAL = THIS->flow_spacing;
+    OUTPUT:
+        RETVAL
+
+void
+ExtrusionPath::append(...)
+    CODE:
+        for (unsigned int i = 1; i < items; i++) {
+            Point p;
+            if (sv_isobject(ST(i)) && (SvTYPE(SvRV(ST(i))) == SVt_PVMG)) {
+                p = *(Point*)SvIV((SV*)SvRV( ST(i) ));
+            } else {
+                perl2point(ST(i), p);
+            }
+            THIS->polyline.points.push_back(p);
+        }
+
+%}
+};
+
+%package{Slic3r::ExtrusionPath};
+%{
+
+IV
+_constant()
+  ALIAS:
+    EXTR_ROLE_PERIMETER                    = erPerimeter
+    EXTR_ROLE_EXTERNAL_PERIMETER           = erExternalPerimeter
+    EXTR_ROLE_OVERHANG_PERIMETER           = erOverhangPerimeter
+    EXTR_ROLE_CONTOUR_INTERNAL_PERIMETER   = erContourInternalPerimeter
+    EXTR_ROLE_FILL                         = erFill
+    EXTR_ROLE_SOLIDFILL                    = erSolidFill
+    EXTR_ROLE_TOPSOLIDFILL                 = erTopSolidFill
+    EXTR_ROLE_BRIDGE                       = erBrige
+    EXTR_ROLE_INTERNALBRIDGE               = erInternalBridge
+    EXTR_ROLE_SKIRT                        = erSkirt
+    EXTR_ROLE_SUPPORTMATERIAL              = erSupportMaterial
+    EXTR_ROLE_GAPFILL                      = erGapFill
+  PROTOTYPE:
+  CODE:
+    RETVAL = ix;
+  OUTPUT: RETVAL
+
+%}
+
diff --git a/xs/xsp/Polygon.xsp b/xs/xsp/Polygon.xsp
new file mode 100644
index 000000000..daffd819c
--- /dev/null
+++ b/xs/xsp/Polygon.xsp
@@ -0,0 +1,29 @@
+%module{Slic3r::XS};
+
+%{
+#include <myinit.h>
+#include "Polygon.hpp"
+%}
+
+%name{Slic3r::Polygon::XS} class Polygon {
+    ~Polygon();
+    Polygon* clone()
+        %code{% const char* CLASS = "Slic3r::Polygon::XS"; RETVAL = new Polygon(*THIS); %};
+    SV* arrayref()
+        %code{% RETVAL = polygon2perl(*THIS); %};
+%{
+
+Polygon*
+Polygon::new(...)
+    CODE:
+        RETVAL = new Polygon ();
+        // ST(0) is class name, ST(1) is first point
+        RETVAL->points.resize(items-1);
+        for (unsigned int i = 1; i < items; i++) {
+            perl2point(ST(i), RETVAL->points[i-1]);
+        }
+    OUTPUT:
+        RETVAL
+
+%}
+};
diff --git a/xs/xsp/Polyline.xsp b/xs/xsp/Polyline.xsp
new file mode 100644
index 000000000..925b799dc
--- /dev/null
+++ b/xs/xsp/Polyline.xsp
@@ -0,0 +1,45 @@
+%module{Slic3r::XS};
+
+%{
+#include <myinit.h>
+#include "Polyline.hpp"
+%}
+
+%name{Slic3r::Polyline::XS} class Polyline {
+    ~Polyline();
+    Polyline* clone()
+        %code{% const char* CLASS = "Slic3r::Polyline::XS"; RETVAL = new Polyline(*THIS); %};
+    SV* arrayref()
+        %code{% RETVAL = polyline2perl(*THIS); %};
+    void pop_back()
+        %code{% THIS->points.pop_back(); %};
+    void reverse();
+%{
+
+Polyline*
+Polyline::new(...)
+    CODE:
+        RETVAL = new Polyline ();
+        // ST(0) is class name, ST(1) is first point
+        RETVAL->points.resize(items-1);
+        for (unsigned int i = 1; i < items; i++) {
+            perl2point(ST(i), RETVAL->points[i-1]);
+        }
+    OUTPUT:
+        RETVAL
+
+void
+Polyline::append(...)
+    CODE:
+        for (unsigned int i = 1; i < items; i++) {
+            Point p;
+            if (sv_isobject(ST(i)) && (SvTYPE(SvRV(ST(i))) == SVt_PVMG)) {
+                p = *(Point*)SvIV((SV*)SvRV( ST(i) ));
+            } else {
+                perl2point(ST(i), p);
+            }
+            THIS->points.push_back(p);
+        }
+
+%}
+};
diff --git a/xs/xsp/my.map b/xs/xsp/my.map
index c5476e220..7e565f533 100644
--- a/xs/xsp/my.map
+++ b/xs/xsp/my.map
@@ -1,8 +1,14 @@
 ZTable*         O_OBJECT
 TriangleMesh*         O_OBJECT
 Point*         O_OBJECT
+Polyline*       O_OBJECT
+Polygon*        O_OBJECT
 ExPolygon*      O_OBJECT
 ExPolygonCollection*    O_OBJECT
-SurfaceType     T_UV
+ExtrusionPath*  O_OBJECT
+ExtrusionLoop*  O_OBJECT
 Surface*        O_OBJECT
 SurfaceCollection*      O_OBJECT
+
+ExtrusionRole     T_UV
+SurfaceType     T_UV
diff --git a/xs/xsp/typemap.xspt b/xs/xsp/typemap.xspt
index fc6f43631..62c73e92b 100644
--- a/xs/xsp/typemap.xspt
+++ b/xs/xsp/typemap.xspt
@@ -4,9 +4,17 @@
 %typemap{AV*};
 %typemap{Point*};
 %typemap{ExPolygon*};
+%typemap{Polyline*};
+%typemap{Polygon*};
 %typemap{SurfaceType}{parsed}{
   %cpp_type{SurfaceType};
   %precall_code{%
     $CVar = (SurfaceType)SvUV($PerlVar);
   %};
-};
\ No newline at end of file
+};
+%typemap{ExtrusionRole}{parsed}{
+  %cpp_type{ExtrusionRole};
+  %precall_code{%
+    $CVar = (ExtrusionRole)SvUV($PerlVar);
+  %};
+};