Reapply correct optimization for simplifiying fill_surfaces before performing the offset. #1325

lib/Slic3r/ExPolygon.pm

@@ -145,15 +145,21 @@ sub clip_line {
     return Boost::Geometry::Utils::polygon_multi_linestring_intersection($self, [$line]);
 }
 
-sub simplify {
+sub simplify_as_polygons {
     my $self = shift;
     my ($tolerance) = @_;
     
     # it would be nice to have a multilinestring_simplify method in B::G::U
-    my @simplified = Slic3r::Geometry::Clipper::simplify_polygons(
+    return Slic3r::Geometry::Clipper::simplify_polygons(
         [ map Boost::Geometry::Utils::linestring_simplify($_, $tolerance), @$self ],
     );
-    return @{ Slic3r::Geometry::Clipper::union_ex([ @simplified ]) };
+}
+
+sub simplify {
+    my $self = shift;
+    my ($tolerance) = @_;
+    
+    return @{ Slic3r::Geometry::Clipper::union_ex([ $self->simplify_as_polygons($tolerance) ]) };
 }
 
 sub scale {

lib/Slic3r/Geometry/Clipper.pm

@@ -150,12 +150,14 @@ sub collapse_ex {
 
 sub simplify_polygon {
     my ($polygon, $pft) = @_;
-    return @{ Math::Clipper::simplify_polygon($polygon, $pft // PFT_NONZERO) };
+    return map Slic3r::Polygon->new(@$_),
+        @{ Math::Clipper::simplify_polygon($polygon, $pft // PFT_NONZERO) };
 }
 
 sub simplify_polygons {
     my ($polygons, $pft) = @_;
-    return @{ Math::Clipper::simplify_polygons($polygons, $pft // PFT_NONZERO) };
+    return map Slic3r::Polygon->new(@$_),
+        @{ Math::Clipper::simplify_polygons($polygons, $pft // PFT_NONZERO) };
 }
 
 sub traverse_pt {

lib/Slic3r/Layer/Region.pm

@@ -209,9 +209,8 @@ sub make_perimeters {
         # and then we offset back and forth by the infill spacing to only consider the
         # non-collapsing regions
         push @{ $self->fill_surfaces },
-            map $_->simplify(&Slic3r::SCALED_RESOLUTION),
             offset2_ex(
-                    \@last,
+                [ map $_->simplify_as_polygons(&Slic3r::SCALED_RESOLUTION), @{union_ex(\@last)} ],
                 -($perimeter_spacing/2 + $infill_spacing),
                 +$infill_spacing,
             );

lib/Slic3r/Polygon.pm

@@ -72,6 +72,8 @@ sub grow {
     return $self->split_at_first_point->grow(@_);
 }
 
+# NOTE that this will turn the polygon to ccw regardless of its 
+# original orientation
 sub simplify {
     my $self = shift;
     return Slic3r::Geometry::Clipper::simplify_polygon( $self->SUPER::simplify(@_) );

t/clean_polylines.t

@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 8;
+plan tests => 10;
 
 BEGIN {
     use FindBin;
@@ -84,6 +84,25 @@ use Slic3r;
     is_deeply \@simplified_ex, [ \@simplified ], 'simplified polygon equals simplified expolygon';
 }
 
+{
+    my $square = Slic3r::Polygon->new(  # ccw
+        [100, 100],
+        [200, 100],
+        [200, 200],
+        [100, 200],
+    );
+    my $hole_in_square = Slic3r::Polygon->new(  # cw
+        [140, 140],
+        [140, 160],
+        [160, 160],
+        [160, 140],
+    );
+    my $expolygon = Slic3r::ExPolygon->new($square, $hole_in_square);
+    my @simplified = $hole_in_square->simplify;
+    is scalar(@simplified), 1, 'hole simplification returns one polygon';
+    ok $simplified[0]->is_counter_clockwise, 'hole simplification turns cw polygon into ccw polygon';
+}
+
 {
     my $circle = [
         [3744.8,8045.8],[3788.1,8061.4],[3940.6,8116.3],[3984.8,8129.2],[4140.6,8174.4],[4185.5,8184.4],[4343.8,8219.9],