Remove features that are too small to be printed

lib/Slic3r/Layer.pm

@@ -304,4 +304,23 @@ sub merge_contiguous_surfaces {
     }
 }
 
+sub remove_small_features {
+    my $self = shift;
+    
+    # for each perimeter, try to get an inwards offset
+    # for a distance equal to half of the extrusion width;
+    # if no offset is possible, then feature is not printable
+    my @good_perimeters = ();
+    foreach my $loop (@{$self->perimeters}) {
+        my $p = $loop->p;
+        @$p = reverse @$p if !is_counter_clockwise($p);
+        my $offsets = offset([$p], -($Slic3r::flow_width / 2 / $Slic3r::resolution), 100, JT_MITER, 2);
+        push @good_perimeters, $loop if @$offsets;
+    }
+    Slic3r::debugf "removed %d unprintable perimeters\n", (@{$self->perimeters} - @good_perimeters) 
+        if @good_perimeters != @{$self->perimeters};
+    
+    @{$self->perimeters} = @good_perimeters;
+}
+
 1;

lib/Slic3r/Print.pm

@@ -91,8 +91,7 @@ sub discover_horizontal_shells {
                 $clipper->clear;
                 
                 # Note: due to floating point math we're going to get some very small
-                # polygons as $internal_polygons; they should be discarded, but a reliable
+                # polygons as $internal_polygons; they will be removed by removed_small_features()
-                # way to detect them is needed, and they seem to be harmless so we keep them for now
                 
                 # assign resulting inner surfaces to layer
                 $self->layers->[$n]->surfaces([]);
@@ -121,6 +120,13 @@ sub discover_horizontal_shells {
     }
 }
 
+# remove perimeters and fill surfaces which are too small to be extruded
+sub remove_small_features {
+    my $self = shift;
+    
+    $_->remove_small_features for @{$self->layers};
+}
+
 sub extrude_perimeters {
     my $self = shift;
     

slic3r.pl

@@ -103,6 +103,7 @@ if ($action eq 'skein') {
     my $t0 = [gettimeofday];
     my $print = $stl_parser->parse_file($input_file);
     $print->extrude_perimeters;
+    $print->remove_small_features;
     $print->extrude_fills;
     
     my $output_file = $input_file;