Better pruning of thin walls to avoid unwanted extra extrusions. Includes regression test. #1794

lib/Slic3r/Layer/Region.pm

@@ -175,14 +175,14 @@ sub make_perimeters {
                     # the minimum thickness of a single loop is:
                     # width/2 + spacing/2 + spacing/2 + width/2
                     @offsets = @{offset2(\@last, -(0.5*$pwidth + 0.5*$pspacing - 1), +(0.5*$pspacing - 1))};
-                
+                    
                     # look for thin walls
                     if ($self->config->thin_walls) {
                         my $diff = diff_ex(
                             \@last,
                             offset(\@offsets, +0.5*$pwidth),
                         );
-                        push @thin_walls, grep abs($_->area) >= $gap_area_threshold, @$diff;
+                        push @thin_walls, @$diff;
                     }
                 } else {
                     @offsets = @{offset2(\@last, -(1.5*$pspacing - 1), +(0.5*$pspacing - 1))};
@@ -305,14 +305,29 @@ sub make_perimeters {
     $self->perimeters->append(@loops);
     
     # process thin walls by collapsing slices to single passes
+    my $min_thin_wall_width = $pwidth/3;
+    my $min_thin_wall_length = 2*$pwidth;
+    @thin_walls = @{offset2_ex([ map @$_, @thin_walls ], -0.5*$min_thin_wall_width, +0.5*$min_thin_wall_width)};
     if (@thin_walls) {
+        if (0) {
+            require "Slic3r/SVG.pm";
+            Slic3r::SVG::output(
+                "thin_walls.svg",
+                no_arrows => 1,
+                expolygons      => \@thin_walls,
+                red_polylines   => [ map $_->polygon->split_at_first_point, @{$self->perimeters} ],
+            );
+        }
+        
         my @p = map $_->medial_axis($pspacing), @thin_walls;
         my @paths = ();
         for my $p (@p) {
+            next if $p->length < $min_thin_wall_length;
             my %params = (
                 role            => EXTR_ROLE_EXTERNAL_PERIMETER,
                 flow_spacing    => $self->perimeter_flow->spacing,
             );
+            printf "len = %s\n", unscale($p->length);
             push @paths, $p->isa('Slic3r::Polygon')
                 ? Slic3r::ExtrusionLoop->new(polygon  => $p, %params)
                 : Slic3r::ExtrusionPath->new(polyline => $p, %params);

lib/Slic3r/SVG.pm

@@ -50,7 +50,7 @@ sub output {
             
             my $g = $svg->group(
                 style => {
-                    'stroke-width' => 2,
+                    'stroke-width' => 0,
                     'stroke' => $colour || 'black',
                     'fill' => ($type !~ /polygons/ ? 'none' : ($colour || 'grey')),
                     'fill-type' => $filltype,
@@ -68,7 +68,7 @@ sub output {
             
             my $g = $svg->group(
                 style => {
-                    'stroke-width' => 2,
+                    'stroke-width' => ($method eq 'polyline') ? 1 : 0,
                     'stroke' => $colour || 'black',
                     'fill' => ($type !~ /polygons/ ? 'none' : ($colour || 'grey')),
                 },

t/thin.t

@@ -0,0 +1,48 @@
+use Test::More tests => 1;
+use strict;
+use warnings;
+
+BEGIN {
+    use FindBin;
+    use lib "$FindBin::Bin/../lib";
+}
+
+use Slic3r;
+use List::Util qw(first);
+use Slic3r::Geometry qw(epsilon);
+use Slic3r::Test;
+
+{
+    my $config = Slic3r::Config->new_from_defaults;
+    $config->set('layer_height', 0.2);
+    $config->set('first_layer_height', '100%');
+    $config->set('extrusion_width', 0.5);
+    $config->set('first_layer_extrusion_width', '200%'); # check this one too
+    $config->set('skirts', 0);
+    $config->set('thin_walls', 1);
+    
+    my $print = Slic3r::Test::init_print('gt2_teeth', config => $config);
+    
+    my %extrusion_paths = ();  # Z => count of continuous extrusions
+    my $extruding = 0;
+    Slic3r::GCode::Reader->new->parse(Slic3r::Test::gcode($print), sub {
+        my ($self, $cmd, $args, $info) = @_;
+        
+        if ($cmd eq 'G1') {
+            if ($info->{extruding} && $info->{dist_XY}) {
+                if (!$extruding) {
+                    $extrusion_paths{$self->Z} //= 0;
+                    $extrusion_paths{$self->Z}++;
+                }
+                $extruding = 1;
+            } else {
+                $extruding = 0;
+            }
+        }
+    });
+    
+    ok !(first { $_ != 3 } values %extrusion_paths),
+        'no superfluous thin walls are generated for toothed profile';
+}
+
+__END__