Raise the thickness threshold used for generating thin walls. TODO: d…

…on't enforce this at the segment level but consider the average thickness of an entire polyline and compare it to the total length. #2910

lib/Slic3r/Layer/PerimeterGenerator.pm

@@ -24,7 +24,6 @@ has '_holes_pt'             => (is => 'rw');
 has '_ext_mm3_per_mm'       => (is => 'rw');
 has '_mm3_per_mm'           => (is => 'rw');
 has '_mm3_per_mm_overhang'  => (is => 'rw');
-has '_thin_wall_polylines'  => (is => 'rw', default => sub { [] });
 
 # generated loops will be put here
 has 'loops'         => (is => 'ro', default => sub { Slic3r::ExtrusionPath::Collection->new });
@@ -133,7 +132,7 @@ sub process {
 
                         # the following offset2 ensures almost nothing in @thin_walls is narrower than $min_width
                         # (actually, something larger than that still may exist due to mitering or other causes)
-                        my $min_width = $ext_pwidth / 4;
+                        my $min_width = $ext_pwidth / 2;
                         @thin_walls = @{offset2_ex($diff, -$min_width/2, +$min_width/2)};
 
                         # the maximum thickness of our thin wall area is equal to the minimum thickness of a single loop
@@ -145,10 +144,9 @@ sub process {
                             require "Slic3r/SVG.pm";
                             Slic3r::SVG::output(
                                 "medial_axis.svg",
-                                no_arrows => 1,
-                                expolygons      => union_ex($diff),
-                                green_polylines => [ map $_->polygon->split_at_first_point, @{$self->perimeters} ],
-                                red_polylines   => $self->_thin_wall_polylines,
+                                no_arrows       => 1,
+                                expolygons      => \@expp,
+                                polylines       => \@thin_walls,
                             );
                         }
                     }

xs/src/libslic3r/Geometry.cpp

@@ -504,7 +504,7 @@ MedialAxis::is_valid_edge(const VD::edge_type& edge) const
         //printf(" => too thin, skipping\n");
         return false;
     }
-
+    
     return true;
 }