diff --git a/lib/Slic3r/Config.pm b/lib/Slic3r/Config.pm
index 41e5fa975..ae166b6c5 100644
--- a/lib/Slic3r/Config.pm
+++ b/lib/Slic3r/Config.pm
@@ -76,7 +76,7 @@ sub load {
     my ($file) = @_;
     
     my $ini = __PACKAGE__->read_ini($file);
-    my $config = __PACKAGE__->new;
+    my $config = $class->new;
     foreach my $opt_key (keys %{$ini->{_}}) {
         ($opt_key, my $value) = _handle_legacy($opt_key, $ini->{_}{$opt_key});
         next if !defined $opt_key;
@@ -88,7 +88,7 @@ sub load {
 sub clone {
     my $self = shift;
     
-    my $new = __PACKAGE__->new;
+    my $new = (ref $self)->new;
     $new->apply($self);
     return $new;
 }
@@ -180,13 +180,14 @@ sub equals {
     return @{ $self->diff($other) } == 0;
 }
 
+# this will *ignore* options not present in both configs
 sub diff {
     my ($self, $other) = @_;
     
     my @diff = ();
     foreach my $opt_key (sort @{$self->get_keys}) {
         push @diff, $opt_key
-            if !$other->has($opt_key) || $other->serialize($opt_key) ne $self->serialize($opt_key);
+            if $other->has($opt_key) && $other->serialize($opt_key) ne $self->serialize($opt_key);
     }
     return [@diff];
 }
@@ -265,27 +266,11 @@ sub validate {
     die "Invalid value for --infill-every-layers\n"
         if $self->infill_every_layers !~ /^\d+$/ || $self->infill_every_layers < 1;
     
-    # --scale
-    die "Invalid value for --scale\n"
-        if $self->scale <= 0;
-    
     # --bed-size
     die "Invalid value for --bed-size\n"
         if !ref $self->bed_size 
             && (!$self->bed_size || $self->bed_size !~ /^\d+,\d+$/);
     
-    # --duplicate-grid
-    die "Invalid value for --duplicate-grid\n"
-        if !ref $self->duplicate_grid 
-            && (!$self->duplicate_grid || $self->duplicate_grid !~ /^\d+,\d+$/);
-    
-    # --duplicate
-    die "Invalid value for --duplicate or --duplicate-grid\n"
-        if !$self->duplicate || $self->duplicate < 1 || !$self->duplicate_grid
-            || (grep !$_, @{$self->duplicate_grid});
-    die "Use either --duplicate or --duplicate-grid (using both doesn't make sense)\n"
-        if $self->duplicate > 1 && $self->duplicate_grid && (grep $_ && $_ > 1, @{$self->duplicate_grid});
-    
     # --skirt-height
     die "Invalid value for --skirt-height\n"
         if $self->skirt_height < -1;  # -1 means as tall as the object
diff --git a/lib/Slic3r/GUI/Plater.pm b/lib/Slic3r/GUI/Plater.pm
index e0b0fcf4a..1fb606c3c 100644
--- a/lib/Slic3r/GUI/Plater.pm
+++ b/lib/Slic3r/GUI/Plater.pm
@@ -754,11 +754,15 @@ sub export_gcode2 {
     } if $Slic3r::have_threads;
     
     my $print = $self->{print};
-    $print->apply_config($config);
-    $print->apply_extra_variables($extra_variables);
+    
     
     eval {
-        $print->config->validate;
+        # this will throw errors if config is not valid
+        $config->validate;
+        
+        $print->apply_config($config);
+        $print->apply_extra_variables($extra_variables);
+        
         $print->validate;
         
         {
diff --git a/lib/Slic3r/GUI/Plater/ObjectSettingsDialog.pm b/lib/Slic3r/GUI/Plater/ObjectSettingsDialog.pm
index e681d7238..b2f5c3ce0 100644
--- a/lib/Slic3r/GUI/Plater/ObjectSettingsDialog.pm
+++ b/lib/Slic3r/GUI/Plater/ObjectSettingsDialog.pm
@@ -114,7 +114,7 @@ sub update_optgroup {
     
     my $config = $self->model_object->config;
     my %categories = ();
-    foreach my $opt_key (keys %$config) {
+    foreach my $opt_key (@{$config->get_keys}) {
         my $category = $Slic3r::Config::Options->{$opt_key}{category};
         $categories{$category} ||= [];
         push @{$categories{$category}}, $opt_key;
@@ -288,31 +288,41 @@ sub new {
     # get unique materials used in this object
     $self->{materials} = [ $self->model_object->unique_materials ];
     
-    # build an OptionsGroup
-    $self->{mapping} = {
-        (map { $self->{materials}[$_] => $_+1 } 0..$#{ $self->{materials} }),   # defaults
-        %{$self->model_object->material_mapping},
-    };
-    my $optgroup = Slic3r::GUI::OptionsGroup->new(
-        parent      => $self,
-        title       => 'Extruders',
-        label_width => 300,
-        options => [
-            map {
-                my $i           = $_;
-                my $material_id = $self->{materials}[$i];
-                {
-                    opt_key     => "material_extruder_$_",
-                    type        => 'i',
-                    label       => $self->model_object->model->get_material_name($material_id),
-                    min         => 1,
-                    default     => $self->{mapping}{$material_id},
-                    on_change   => sub { $self->{mapping}{$material_id} = $_[0] },
-                }
-            } 0..$#{ $self->{materials} }
-        ],
-    );
-    $self->{sizer}->Add($optgroup->sizer, 0, wxEXPAND | wxALL, 10);
+    # get the current mapping
+    $self->{mapping} = {};
+    foreach my $material_id (@{ $self->{materials}}) {
+        my $config = $self->model_object->model->materials->{ $material_id }->config;
+        $self->{mapping}{$material_id} = ($config->perimeter_extruder // 0) + 1;
+    }
+    
+    if (@{$self->{materials}} > 0) {
+        # build an OptionsGroup
+        my $optgroup = Slic3r::GUI::OptionsGroup->new(
+            parent      => $self,
+            title       => 'Extruders',
+            label_width => 300,
+            options => [
+                map {
+                    my $i           = $_;
+                    my $material_id = $self->{materials}[$i];
+                    {
+                        opt_key     => "material_extruder_$_",
+                        type        => 'i',
+                        label       => $self->model_object->model->get_material_name($material_id),
+                        min         => 1,
+                        default     => $self->{mapping}{$material_id} // 1,
+                        on_change   => sub { $self->{mapping}{$material_id} = $_[0] },
+                    }
+                } 0..$#{ $self->{materials} }
+            ],
+        );
+        $self->{sizer}->Add($optgroup->sizer, 0, wxEXPAND | wxALL, 10);
+    } else {
+        my $label = Wx::StaticText->new($self, -1, "This object does not contain named materials.",
+            wxDefaultPosition, [-1, 25]);
+        $label->SetFont(Wx::SystemSettings::GetFont(wxSYS_DEFAULT_GUI_FONT));
+        $self->{sizer}->Add($label, 0, wxEXPAND | wxTOP | wxLEFT | wxRIGHT, 10);
+    }
     
     $self->SetSizer($self->{sizer});
     $self->{sizer}->SetSizeHints($self);
@@ -324,10 +334,10 @@ sub Closing {
     my $self = shift;
     
     # save mappings into the plater object
-    foreach my $volume (@{$self->model_object}) {
+    foreach my $volume (@{$self->model_object->volumes}) {
         if (defined $volume->material_id) {
             my $config = $self->model_object->model->materials->{ $volume->material_id }->config;
-            $config->set('extruder', $self->{mapping}{ $volume->material_id });
+            $config->set('extruder', $self->{mapping}{ $volume->material_id }-1);
         }
     }
 }
diff --git a/lib/Slic3r/Model.pm b/lib/Slic3r/Model.pm
index 401deb47e..3cbd97493 100644
--- a/lib/Slic3r/Model.pm
+++ b/lib/Slic3r/Model.pm
@@ -54,10 +54,11 @@ sub add_object {
             
             if (defined $volume->material_id) {
                 #  merge material attributes (should we rename materials in case of duplicates?)
-                $self->set_material($volume->material_id, {
-                    %{ $object->model->materials->{$volume->material_id} },
-                    %{ $self->materials->{$volume->material_id} || {} },
-                });
+                my %attributes = %{ $object->model->materials->{$volume->material_id}->attributes };
+                if (exists $self->materials->{$volume->material_id}) {
+                    %attributes = (%attributes, %{ $self->materials->{$volume->material_id}->attributes });
+                }
+                $self->set_material($volume->material_id, {%attributes});
             }
         }
         
@@ -478,7 +479,8 @@ sub unique_materials {
     my $self = shift;
     
     my %materials = ();
-    $materials{ $_->material_id // '_' } = 1 for @{$self->volumes};
+    $materials{ $_->material_id } = 1
+        for grep { defined $_->material_id } @{$self->volumes};
     return sort keys %materials;
 }
 
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index d44a06b6c..c0ed2e11f 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -31,9 +31,87 @@ has 'brim' => (is => 'rw', default => sub { Slic3r::ExtrusionPath::Collection->n
 sub apply_config {
     my ($self, $config) = @_;
     
-    $self->config->apply_dynamic($config);
+    # handle changes to print config
+    my $print_diff = $self->config->diff($config);
+    if (@$print_diff) {
+        $self->config->apply_dynamic($config);
+        
+        # TODO: only invalidate changed steps
+        $self->_state->invalidate_all;
+    }
+    
+    # handle changes to object config defaults
     $self->default_object_config->apply_dynamic($config);
+    foreach my $object (@{$self->objects}) {
+        # we don't assume that $config contains a full ObjectConfig,
+        # so we base it on the current print-wise default
+        my $new = $self->default_object_config->clone;
+        
+        # we override the new config with object-specific options
+        $new->apply_dynamic($object->model_object->config);
+        
+        # check whether the new config is different from the current one
+        my $diff = $object->config->diff($new);
+        if (@$diff) {
+            $object->config->apply($new);
+            # TODO: only invalidate changed steps
+            $object->_state->invalidate_all;
+        }
+    }
+    
+    # handle changes to regions config defaults
     $self->default_region_config->apply_dynamic($config);
+    
+    # check whether after applying the new region config defaults to all existing regions
+    # they still have distinct configs; if not we need to re-add objects in order to 
+    # merge the now-equal regions
+    
+    # first compute the transformed region configs
+    my @new_region_configs = ();
+    foreach my $region_id (0..$#{$self->regions}) {
+        my $new = $self->default_region_config->clone;
+        foreach my $object (@{$self->objects}) {
+            foreach my $volume_id (@{ $object->region_volumes->[$region_id] }) {
+                my $volume = $object->model_object->volumes->[$volume_id];
+                next if !defined $volume->material_id;
+                my $material = $object->model_object->model->materials->{$volume->material_id};
+                $new->apply_dynamic($material->config);
+            }
+        }
+        push @new_region_configs, $new;
+    }
+    
+    # then find the first pair of identical configs
+    my $have_identical_configs = 0;
+    my $region_diff = [];
+    for my $i (0..$#new_region_configs) {
+        for my $j (($i+1)..$#new_region_configs) {
+            if ($new_region_configs[$i]->equals($new_region_configs[$j])) {
+                $have_identical_configs = 1;
+            }
+        }
+        my $diff = $self->regions->[$i]->config->diff($new_region_configs[$i]);
+        push @$region_diff, @$diff;
+    }
+    
+    if ($have_identical_configs) {
+        # okay, the current subdivision of regions does not make sense anymore.
+        # we need to remove all objects and re-add them
+        my @model_objects = map $_->model_object, @{$self->object};
+        $self->delete_all_objects;
+        $self->add_model_object($_) for @model_objects;
+    } elsif (@$region_diff > 0) {
+        # if there are no identical regions even after applying the change in 
+        # region config defaults, but at least one region config option changed,
+        # store the new region configs and invalidate
+        # the affected step(s)
+        foreach my $region_id (0..$#{$self->regions}) {
+            $self->regions->[$region_id]->config->apply($new_region_configs[$region_id]);
+        }
+        
+        # TODO: only invalidate changed steps
+        $_->_state->invalidate_all for @{$self->objects};
+    }
 }
 
 sub has_support_material {
@@ -991,7 +1069,7 @@ sub auto_assign_extruders {
         if (defined $volume->material_id) {
             my $material = $model_object->model->materials->{ $volume->material_id };
             my $config = $material->config;
-            $config->set_ifndef('perimeters_extruder', $i);
+            $config->set_ifndef('perimeter_extruder', $i);
             $config->set_ifndef('infill_extruder', $i);
             $config->set_ifndef('support_material_extruder', $i);
             $config->set_ifndef('support_material_interface_extruder', $i);
diff --git a/xs/src/Config.hpp b/xs/src/Config.hpp
index 9b9a7bf95..3af99a448 100644
--- a/xs/src/Config.hpp
+++ b/xs/src/Config.hpp
@@ -354,6 +354,7 @@ class ConfigOptionDef
     public:
     ConfigOptionType type;
     std::string label;
+    std::string full_label;
     std::string category;
     std::string tooltip;
     std::string sidetext;
@@ -361,7 +362,6 @@ class ConfigOptionDef
     std::string scope;
     t_config_option_key ratio_over;
     bool multiline;
-    bool full_label;
     bool full_width;
     bool readonly;
     int height;
diff --git a/xs/src/Print.cpp b/xs/src/Print.cpp
index f5dd9fe7d..539206c49 100644
--- a/xs/src/Print.cpp
+++ b/xs/src/Print.cpp
@@ -33,4 +33,11 @@ PrintState::invalidate(PrintStep step)
     this->_done.erase(step);
 }
 
+void
+PrintState::invalidate_all()
+{
+    this->_started.clear();
+    this->_done.clear();
+}
+
 }
diff --git a/xs/src/Print.hpp b/xs/src/Print.hpp
index a79d544df..9e93408b2 100644
--- a/xs/src/Print.hpp
+++ b/xs/src/Print.hpp
@@ -22,6 +22,7 @@ class PrintState
     void set_started(PrintStep step);
     void set_done(PrintStep step);
     void invalidate(PrintStep step);
+    void invalidate_all();
 };
 
 }
diff --git a/xs/src/PrintConfig.hpp b/xs/src/PrintConfig.hpp
index dd9f2633c..8ac01f504 100644
--- a/xs/src/PrintConfig.hpp
+++ b/xs/src/PrintConfig.hpp
@@ -61,7 +61,7 @@ class PrintConfigDef
         Options["bed_temperature"].tooltip = "Bed temperature for layers after the first one. Set this to zero to disable bed temperature control commands in the output.";
         Options["bed_temperature"].sidetext = "°C";
         Options["bed_temperature"].cli = "bed-temperature=i";
-        Options["bed_temperature"].full_label = true;
+        Options["bed_temperature"].full_label = "Bed temperature";
         Options["bed_temperature"].max = 300;
 
         Options["bottom_solid_layers"].type = coInt;
@@ -70,7 +70,7 @@ class PrintConfigDef
         Options["bottom_solid_layers"].tooltip = "Number of solid layers to generate on bottom surfaces.";
         Options["bottom_solid_layers"].cli = "bottom-solid-layers=i";
         Options["bottom_solid_layers"].scope = "object";
-        Options["bottom_solid_layers"].full_label = true;
+        Options["bottom_solid_layers"].full_label = "Bottom solid layers";
 
         Options["bridge_acceleration"].type = coFloat;
         Options["bridge_acceleration"].label = "Bridge";
@@ -346,7 +346,7 @@ class PrintConfigDef
         Options["infill_every_layers"].sidetext = "layers";
         Options["infill_every_layers"].cli = "infill-every-layers=i";
         Options["infill_every_layers"].scope = "object";
-        Options["infill_every_layers"].full_label = true;
+        Options["infill_every_layers"].full_label = "Combine infill every n layers";
         Options["infill_every_layers"].min = 1;
 
         Options["infill_extruder"].type = coInt;
@@ -715,7 +715,7 @@ class PrintConfigDef
         Options["support_material_enforce_layers"].sidetext = "layers";
         Options["support_material_enforce_layers"].cli = "support-material-enforce-layers=f";
         Options["support_material_enforce_layers"].scope = "object";
-        Options["support_material_enforce_layers"].full_label = true;
+        Options["support_material_enforce_layers"].full_label = "Enforce support for the first n layers";
 
         Options["support_material_extruder"].type = coInt;
         Options["support_material_extruder"].label = "Support material extruder";
@@ -789,7 +789,7 @@ class PrintConfigDef
         Options["temperature"].tooltip = "Extruder temperature for layers after the first one. Set this to zero to disable temperature control commands in the output.";
         Options["temperature"].sidetext = "°C";
         Options["temperature"].cli = "temperature=i@";
-        Options["temperature"].full_label = true;
+        Options["temperature"].full_label = "Temperature";
         Options["temperature"].max = 400;
 
         Options["thin_walls"].type = coBool;
@@ -835,7 +835,7 @@ class PrintConfigDef
         Options["top_solid_layers"].tooltip = "Number of solid layers to generate on top surfaces.";
         Options["top_solid_layers"].cli = "top-solid-layers=i";
         Options["top_solid_layers"].scope = "object";
-        Options["top_solid_layers"].full_label = true;
+        Options["top_solid_layers"].full_label = "Top solid layers";
 
         Options["travel_speed"].type = coFloat;
         Options["travel_speed"].label = "Travel";
diff --git a/xs/xsp/Config.xsp b/xs/xsp/Config.xsp
index b7f6f3ec8..18deda295 100644
--- a/xs/xsp/Config.xsp
+++ b/xs/xsp/Config.xsp
@@ -142,6 +142,7 @@ print_config_def()
             }
             (void)hv_stores( hv, "type",        newSVpv(opt_type, 0) );
             (void)hv_stores( hv, "label",       newSVpvn(optdef->label.c_str(), optdef->label.length()) );
+            (void)hv_stores( hv, "full_label",  newSVpvn(optdef->full_label.c_str(), optdef->full_label.length()) );
             (void)hv_stores( hv, "category",    newSVpvn(optdef->category.c_str(), optdef->category.length()) );
             (void)hv_stores( hv, "tooltip",     newSVpvn(optdef->tooltip.c_str(), optdef->tooltip.length()) );
             (void)hv_stores( hv, "sidetext",    newSVpvn(optdef->sidetext.c_str(), optdef->sidetext.length()) );
@@ -149,7 +150,6 @@ print_config_def()
             (void)hv_stores( hv, "scope",       newSVpvn(optdef->scope.c_str(), optdef->scope.length()) );
             (void)hv_stores( hv, "ratio_over",  newSVpvn(optdef->ratio_over.c_str(), optdef->ratio_over.length()) );
             (void)hv_stores( hv, "multiline",   newSViv(optdef->multiline ? 1 : 0) );
-            (void)hv_stores( hv, "full_label",  newSViv(optdef->full_label ? 1 : 0) );
             (void)hv_stores( hv, "full_width",  newSViv(optdef->full_width ? 1 : 0) );
             (void)hv_stores( hv, "readonly",    newSViv(optdef->readonly ? 1 : 0) );
             (void)hv_stores( hv, "height",      newSViv(optdef->height) );
diff --git a/xs/xsp/Print.xsp b/xs/xsp/Print.xsp
index 0eef527ea..25f52a71c 100644
--- a/xs/xsp/Print.xsp
+++ b/xs/xsp/Print.xsp
@@ -13,6 +13,7 @@
     void set_started(PrintStep step);
     void set_done(PrintStep step);
     void invalidate(PrintStep step);
+    void invalidate_all();
 %{
 
 %}