Bugfix: simplification of support areas could lead to complex polygons with bad orientation, thus causing wrong pattern clipping. #1032

lib/Slic3r/ExPolygon.pm

@@ -5,6 +5,7 @@ use warnings;
 # an ExPolygon is a polygon with holes
 
 use Boost::Geometry::Utils;
+use List::Util qw(first);
 use Math::Geometry::Voronoi;
 use Slic3r::Geometry qw(X Y A B point_in_polygon same_line line_length epsilon);
 use Slic3r::Geometry::Clipper qw(union_ex JT_MITER);
@@ -54,6 +55,13 @@ sub clipper_expolygon {
     };
 }
 
+sub is_valid {
+    my $self = shift;
+    return (!first { !$_->is_valid } @$self)
+        && $self->contour->is_counter_clockwise
+        && (!first { $_->is_counter_clockwise } $self->holes);
+}
+
 sub boost_polygon {
     my $self = shift;
     return Boost::Geometry::Utils::polygon(@$self);

lib/Slic3r/Geometry/Clipper.pm

@@ -4,7 +4,7 @@ use warnings;
 
 require Exporter;
 our @ISA = qw(Exporter);
-our @EXPORT_OK = qw(safety_offset offset offset_ex
+our @EXPORT_OK = qw(safety_offset offset offset_ex collapse_ex
     diff_ex diff union_ex intersection_ex xor_ex PFT_EVENODD JT_MITER JT_ROUND
     JT_SQUARE is_counter_clockwise);
 
@@ -83,4 +83,13 @@ sub xor_ex {
     ];
 }
 
+sub collapse_ex {
+    my ($polygons, $width) = @_;
+    my @result = offset(
+        [ offset($polygons, -$width/2,) ],
+        +$width/2,
+    );
+    return union_ex([@result]);
+}
+
 1;

lib/Slic3r/Print/Object.pm

@@ -4,7 +4,7 @@ use Moo;
 use List::Util qw(min sum first);
 use Slic3r::ExtrusionPath ':roles';
 use Slic3r::Geometry qw(Z PI scale unscale deg2rad rad2deg scaled_epsilon);
-use Slic3r::Geometry::Clipper qw(diff_ex intersection_ex union_ex offset);
+use Slic3r::Geometry::Clipper qw(diff_ex intersection_ex union_ex offset collapse_ex);
 use Slic3r::Surface ':types';
 
 has 'print'             => (is => 'ro', weak_ref => 1, required => 1);
@@ -774,6 +774,7 @@ sub generate_support_material {
                 [ map @$_, @{ $upper_layers_overhangs[-1] || [] } ],
                 [ map @$_, @current_layer_offsetted_slices ],
             );
+            $layers_contact_areas{$i} = collapse_ex([ map @$_, @{$layers_contact_areas{$i}} ], $flow->scaled_width);
             $_->simplify($flow->scaled_spacing) for @{$layers_contact_areas{$i}};
             
             # to define interface regions of this layer we consider the overhangs of all the upper layers
@@ -785,6 +786,7 @@ sub generate_support_material {
                     (map @$_, @{ $layers_contact_areas{$i} }),
                 ],
             );
+            $layers_interfaces{$i} = collapse_ex([ map @$_, @{$layers_interfaces{$i}} ], $flow->scaled_width);
             $_->simplify($flow->scaled_spacing) for @{$layers_interfaces{$i}};
             
             # generate support material in current layer (for upper layers)
@@ -804,6 +806,7 @@ sub generate_support_material {
                     (map @$_, @{ $layers_interfaces{$i} }),
                 ],
             );
+            $layers{$i} = collapse_ex([ map @$_, @{$layers{$i}} ], $flow->scaled_width);
             $_->simplify($flow->scaled_spacing) for @{$layers{$i}};
             
             # get layer overhangs and put them into queue for adding support inside lower layers;