Fix of git #3293: More efficient GCode export

This fixes two problems of repeatedly copying data from the C++ layer
to perl, by factoring the copying out of an inner loop.

lib/Slic3r/Print/GCode.pm

@@ -35,7 +35,7 @@ sub BUILD {
             $layer_count = sum(map { $_->total_layer_count } @{$self->objects});
         }
     
-        # set up our helper object
+        # set up our helper object: This is a C++ Slic3r::GCode instance.
         my $gcodegen = Slic3r::GCode->new;
         $self->_gcodegen($gcodegen);
         $gcodegen->set_placeholder_parser($self->placeholder_parser);
@@ -115,20 +115,21 @@ sub BUILD {
         if $self->config->pressure_advance > 0;
 }
 
+# Export a G-code for the complete print.
 sub export {
     my ($self) = @_;
     
     my $fh          = $self->fh;
     my $gcodegen    = $self->_gcodegen;
     
-    # write some information
+    # Write information on the generator.
     my @lt = localtime;
     printf $fh "; generated by Slic3r $Slic3r::VERSION on %04d-%02d-%02d at %02d:%02d:%02d\n\n",
         $lt[5] + 1900, $lt[4]+1, $lt[3], $lt[2], $lt[1], $lt[0];
-
+    # Write notes (content of the Print Settings tab -> Notes)
     print $fh "; $_\n" foreach split /\R/, $self->config->notes;
     print $fh "\n" if $self->config->notes;
-    
+    # Write some terse information on the slicing parameters.
     my $first_object = $self->objects->[0];
     my $layer_height = $first_object->config->layer_height;
     for my $region_id (0..$#{$self->print->regions}) {
@@ -155,6 +156,7 @@ sub export {
     # prepare the helper object for replacing placeholders in custom G-code and output filename
     $self->placeholder_parser->update_timestamp;
     
+    # disable fan
     print $fh $gcodegen->writer->set_fan(0, 1)
         if $self->config->cooling && $self->config->disable_fan_first_layers;
     
@@ -340,6 +342,9 @@ sub _print_first_layer_temperature {
     }
 }
 
+# Called per object's layer.
+# First a $gcode string is collected,
+# then filtered and finally written to a file $fh.
 sub process_layer {
     my $self = shift;
     my ($layer, $object_copies) = @_;
@@ -485,6 +490,20 @@ sub process_layer {
         # group extrusions by extruder and then by island
         my %by_extruder = ();  # extruder_id => [ { perimeters => \@perimeters, infill => \@infill } ]
 
+        my $n_slices = $#{$layer->slices};
+        my @layer_surface_bboxes = ();
+        for my $i (0 .. $n_slices) {
+            push @layer_surface_bboxes, $layer->slices->[$i]->contour->bounding_box;
+        }
+        my $point_inside_surface = sub { 
+            my ($i, $point) = @_;
+            my $bbox = $layer_surface_bboxes[$i];
+            return 
+                $point->x >= $bbox->x_min && $point->x < $bbox->x_max &&
+                $point->y >= $bbox->y_min && $point->y < $bbox->y_max &&
+                $layer->slices->[$i]->contour->contains_point($point);
+        };
+
         foreach my $region_id (0..($self->print->region_count-1)) {
             my $layerm = $layer->regions->[$region_id] or next;
             my $region = $self->print->get_region($region_id);
@@ -499,9 +518,12 @@ sub process_layer {
                     $by_extruder{$extruder_id} //= [];
                     
                     # $perimeter_coll is an ExtrusionPath::Collection object representing a single slice
-                    for my $i (0 .. $#{$layer->slices}) {
+                    for my $i (0 .. $n_slices) {
-                        if ($i == $#{$layer->slices}
+                        if (
-                            || $layer->slices->[$i]->contour->contains_point($perimeter_coll->first_point)) {
+                            # $perimeter_coll->first_point does not fit inside any slice
+                            $i == $n_slices 
+                            # $perimeter_coll->first_point fits inside ith slice
+                            || $point_inside_surface->($i, $perimeter_coll->first_point)) {
                             $by_extruder{$extruder_id}[$i] //= { perimeters => {} };
                             $by_extruder{$extruder_id}[$i]{perimeters}{$region_id} //= [];
                             push @{ $by_extruder{$extruder_id}[$i]{perimeters}{$region_id} }, @$perimeter_coll;
@@ -527,9 +549,9 @@ sub process_layer {
                 $by_extruder{$extruder_id} //= [];
                 
                 # $fill is an ExtrusionPath::Collection object
-                for my $i (0 .. $#{$layer->slices}) {
+                for my $i (0 .. $n_slices) {
-                    if ($i == $#{$layer->slices}
+                    if ($i == $n_slices
-                        || $layer->slices->[$i]->contour->contains_point($fill->first_point)) {
+                        || $point_inside_surface->($i, $fill->first_point)) {
                         $by_extruder{$extruder_id}[$i] //= { infill => {} };
                         $by_extruder{$extruder_id}[$i]{infill}{$region_id} //= [];
                         push @{ $by_extruder{$extruder_id}[$i]{infill}{$region_id} }, $fill;
@@ -583,6 +605,7 @@ sub process_layer {
     print {$self->fh} $self->filter($gcode);
 }
 
+# Extrude perimeters: Decide where to put seams (hide or align seams).
 sub _extrude_perimeters {
     my ($self, $entities_by_region) = @_;
     
@@ -595,6 +618,7 @@ sub _extrude_perimeters {
     return $gcode;
 }
 
+# Chain the paths hierarchically by a greedy algorithm to minimize a travel distance.
 sub _extrude_infill {
     my ($self, $entities_by_region) = @_;
     

lib/Slic3r/Print/Object.pm

@@ -393,6 +393,10 @@ sub make_perimeters {
         for my $i (0 .. ($self->layer_count - 2)) {
             my $layerm                  = $self->get_layer($i)->get_region($region_id);
             my $upper_layerm            = $self->get_layer($i+1)->get_region($region_id);
+            my $upper_layerm_polygons   = [ map $_->p, @{$upper_layerm->slices} ];
+            # Filter upper layer polygons in intersection_ppl by their bounding boxes?
+            # my $upper_layerm_poly_bboxes= [ map $_->bounding_box, @{$upper_layerm_polygons} ];
+            my $total_loop_length       = sum(map $_->length, @$upper_layerm_polygons) // 0;
             
             my $perimeter_spacing       = $layerm->flow(FLOW_ROLE_PERIMETER)->scaled_spacing;
             my $ext_perimeter_flow      = $layerm->flow(FLOW_ROLE_EXTERNAL_PERIMETER);
@@ -415,12 +419,11 @@ sub make_perimeters {
                     
                     # check whether a portion of the upper slices falls inside the critical area
                     my $intersection = intersection_ppl(
-                        [ map $_->p, @{$upper_layerm->slices} ],
+                        $upper_layerm_polygons,
                         $critical_area,
                     );
                     
                     # only add an additional loop if at least 30% of the slice loop would benefit from it
-                    my $total_loop_length = sum(map $_->length, map $_->p, @{$upper_layerm->slices}) // 0;
                     my $total_intersection_length = sum(map $_->length, @$intersection) // 0;
                     last unless $total_intersection_length > $total_loop_length*0.3;