Enable retraction for support material too, but only when moving away from support islands. #831

lib/Slic3r/GCode.pm

@@ -163,10 +163,11 @@ sub extrude_path {
     my $gcode = "";
     
     # skip retract for support material
-    if ($path->role != EXTR_ROLE_SUPPORTMATERIAL) {
+    {
         # retract if distance from previous position is greater or equal to the one specified by the user
         my $travel = Slic3r::Line->new($self->last_pos->clone, $path->points->[0]->clone);
-        if ($travel->length >= scale $self->extruder->retract_before_travel) {
+        if ($travel->length >= scale $self->extruder->retract_before_travel
+            && ($path->role != EXTR_ROLE_SUPPORTMATERIAL || !$self->layer->support_islands_enclose_line($travel))) {
             # move travel back to original layer coordinates.
             # note that we're only considering the current object's islands, while we should
             # build a more complete configuration space

lib/Slic3r/Layer.pm

@@ -1,6 +1,7 @@
 package Slic3r::Layer;
 use Moo;
 
+use List::Util qw(first);
 use Slic3r::Geometry::Clipper qw(union_ex);
 
 has 'id'                => (is => 'rw', required => 1, trigger => 1); # sequential number of layer, 0-based
@@ -18,6 +19,7 @@ has 'flow'              => (is => 'ro', default => sub { $Slic3r::flow });
 has 'slices'            => (is => 'rw');
 
 # ordered collection of extrusion paths to fill surfaces for support material
+has 'support_islands'           => (is => 'rw');
 has 'support_fills'             => (is => 'rw');
 has 'support_interface_fills'   => (is => 'rw');
 
@@ -102,4 +104,10 @@ sub make_perimeters {
     $_->make_perimeters for @{$self->regions};
 }
 
+sub support_islands_enclose_line {
+    my $self = shift;
+    my ($line) = @_;
+    return (first { $_->encloses_line($line) } @{$self->support_islands}) ? 1 : 0;
+}
+
 1;

lib/Slic3r/Print/Object.pm

@@ -626,39 +626,40 @@ sub generate_support_material {
             };
             return @paths;
         };
-        my %layer_paths = ();
+        my %layer_paths             = ();
-        my %layer_interface_paths = ();
+        my %layer_interface_paths   = ();
+        my %layer_islands           = ();
         my $process_layer = sub {
             my ($layer_id) = @_;
             
             my $layer = $self->layers->[$layer_id];
             my $paths           = [ $clip_pattern->($layer_id, $layers{$layer_id}, $layer->height) ];
             my $interface_paths = [ $clip_pattern->($layer_id, $layers_interfaces{$layer_id}, $layer->support_material_interface_height) ];
-            return ($paths, $interface_paths);
+            my $islands         = union_ex([ map @$_, map @$_, $layers{$layer_id}, $layers_interfaces{$layer_id} ]);
+            return ($paths, $interface_paths, $islands);
         };
         Slic3r::parallelize(
             items => [ keys %layers ],
             thread_cb => sub {
                 my $q = shift;
-                my $paths = {};
+                my $result = {};
-                my $interface_paths = {};
                 while (defined (my $layer_id = $q->dequeue)) {
-                    ($paths->{$layer_id}, $interface_paths->{$layer_id}) = $process_layer->($layer_id);
+                    $result->{$layer_id} = [ $process_layer->($layer_id) ];
                 }
-                return [ $paths, $interface_paths ];
+                return $result;
             },
             collect_cb => sub {
-                my $paths = shift;
+                my $result = shift;
-                $layer_paths{$_}            = $paths->[0]{$_} for keys %{$paths->[0]};
+                ($layer_paths{$_}, $layer_interface_paths{$_}, $layer_islands{$_}) = @{$result->{$_}} for keys %$result;
-                $layer_interface_paths{$_}  = $paths->[1]{$_} for keys %{$paths->[1]};
             },
             no_threads_cb => sub {
-                ($layer_paths{$_}, $layer_interface_paths{$_}) = $process_layer->($_) for keys %layers;
+                ($layer_paths{$_}, $layer_interface_paths{$_}, $layer_islands{$_}) = $process_layer->($_) for keys %layers;
             },
         );
         
         foreach my $layer_id (keys %layer_paths) {
             my $layer = $self->layers->[$layer_id];
+            $layer->support_islands($layer_islands{$layer_id});
             $layer->support_fills(Slic3r::ExtrusionPath::Collection->new);
             $layer->support_interface_fills(Slic3r::ExtrusionPath::Collection->new);
             push @{$layer->support_fills->paths}, @{$layer_paths{$layer_id}};