Bugfix: many thin walls were not detected correctly. #313

lib/Slic3r/ExPolygon.pm

@@ -215,54 +215,73 @@ sub medial_axis {
     }
     return undef if !@skeleton_lines;
     
-    # now build a single polyline
-    my $polyline = [];
+    # now walk along the medial axis and build continuos polylines or polygons
+    my @polylines = ();
     {
-        my %pointmap = ();
-        foreach my $line (@skeleton_lines) {
-            foreach my $point_id (@$line) {
-                $pointmap{$point_id} ||= [];
-                push @{$pointmap{$point_id}}, $line;
+        # build a map of line endpoints
+        my %pointmap = ();  # point_idx => [line_idx, line_idx ...]
+        for my $line_idx (0 .. $#skeleton_lines) {
+            for my $point_idx (@{$skeleton_lines[$line_idx]}) {
+                $pointmap{$point_idx} ||= [];
+                push @{$pointmap{$point_idx}}, $line_idx;
             }
         }
         
-        # start from a point having only one line
-        foreach my $point_id (keys %pointmap) {
-            if (@{$pointmap{$point_id}} == 1) {
-                push @$polyline, grep $_ ne $point_id, map @$_, shift @{$pointmap{$point_id}};
-                last;
-            }
-        }
+        # build the list of available lines
+        my %spare_lines = map {$_ => 1} (0 .. $#skeleton_lines);
         
-        # if no such point is found, pick a random one
-        push @$polyline, shift @{ +(values %pointmap)[0][0] } if !@$polyline;
+        CYCLE: while (%spare_lines) {
+            push @polylines, [];
+            my $polyline = $polylines[-1];
+            
+            # start from a random line
+            my $first_line_idx = +(keys %spare_lines)[0];
+            delete $spare_lines{$first_line_idx};
+            push @$polyline, @{ $skeleton_lines[$first_line_idx] };
             
-        my %visited_lines = ();
             while (1) {
                 my $last_point_id = $polyline->[-1];
+                my $lines_starting_here = $pointmap{$last_point_id};
                 
-            shift @{ $pointmap{$last_point_id} }
-                while @{ $pointmap{$last_point_id} } && $visited_lines{$pointmap{$last_point_id}[0]};
-            my $next_line = shift @{ $pointmap{$last_point_id} } or last;
-            $visited_lines{$next_line} = 1;
-            push @$polyline, grep $_ ne $last_point_id, @$next_line;
+                # remove all the visited lines from the array
+                shift @$lines_starting_here
+                    while @$lines_starting_here && !$spare_lines{$lines_starting_here->[0]};
+                
+                # do we have a line starting here?
+                my $next_line_idx = shift @$lines_starting_here;
+                if (!defined $next_line_idx) {
+                    delete $pointmap{$last_point_id};
+                    next CYCLE;
+                }
+                
+                # line is not available anymore
+                delete $spare_lines{$next_line_idx};
+                
+                # add the other point to our polyline and continue walking
+                push @$polyline, grep $_ ne $last_point_id, @{$skeleton_lines[$next_line_idx]};
             }
         }
+    }
+    
+    my @result = ();
+    foreach my $polyline (@polylines) {
+        next unless @$polyline >= 2;
         
         # now replace point indexes with coordinates
         @$polyline = map $vertices->[$_], @$polyline;
         
         # cleanup
-    Slic3r::Geometry::polyline_remove_short_segments($polyline, $width / 2);
         $polyline = Slic3r::Geometry::douglas_peucker($polyline, $width / 7);
-    Slic3r::Geometry::polyline_remove_parallel_continuous_edges($polyline);
         
         if (Slic3r::Geometry::same_point($polyline->[0], $polyline->[-1])) {
-        return undef if @$polyline == 2;
-        return Slic3r::Polygon->new(@$polyline[0..$#$polyline-1]);
+            next if @$polyline == 2;
+            push @result, Slic3r::Polygon->new(@$polyline[0..$#$polyline-1]);
         } else {
-        return Slic3r::Polyline->new($polyline);
+            push @result, Slic3r::Polyline->new($polyline);
         }
     }
     
+    return @result;
+}
+
 1;

lib/Slic3r/Layer.pm

@@ -174,7 +174,6 @@ sub make_surfaces {
             @$diff = grep $_->area > ($area_threshold), @$diff;
             
             push @{$self->thin_walls},
-                grep $_,
                 map $_->medial_axis(scale $self->perimeters_flow->width),
                 @$diff;
             
@@ -260,7 +259,6 @@ sub make_perimeters {
                 [ map @$_, map $_->offset_ex(+$distance/2), @fill_boundaries ],
             );
             push @{ $self->thin_fills },
-                grep $_,
                 map $_->medial_axis(scale $self->perimeters_flow->width),
                 @$small_gaps if 0;
         }
@@ -320,13 +318,18 @@ sub make_perimeters {
     }
     
     # add thin walls as perimeters
+    {
+        my @thin_paths = ();
         for (@{ $self->thin_walls }) {
             if ($_->isa('Slic3r::Polygon')) {
-            push @{ $self->perimeters }, Slic3r::ExtrusionLoop->new(polygon => $_, role => EXTR_ROLE_PERIMETER);
+                push @thin_paths, Slic3r::ExtrusionLoop->new(polygon => $_, role => EXTR_ROLE_PERIMETER);
             } else {
-            push @{ $self->perimeters }, Slic3r::ExtrusionPath->new(polyline => $_, role => EXTR_ROLE_PERIMETER);
+                push @thin_paths, Slic3r::ExtrusionPath->new(polyline => $_, role => EXTR_ROLE_PERIMETER);
             }
         }
+        my $collection = Slic3r::ExtrusionPath::Collection->new(paths => \@thin_paths);
+        push @{ $self->perimeters }, $collection->shortest_path;
+    }
 }
 
 sub add_perimeter {