From 8aca7172092b2192d872d63772bab8043e9dd4b9 Mon Sep 17 00:00:00 2001
From: Alessandro Ranellucci <aar@cpan.org>
Date: Wed, 16 Nov 2011 16:35:20 +0100
Subject: [PATCH] Print solid infill without cutting an internal surface under
 small regions such as pillars. #39

---
 lib/Slic3r/ExPolygon.pm |  8 +++++++-
 lib/Slic3r/Perimeter.pm |  4 ++--
 lib/Slic3r/Polygon.pm   |  5 +++++
 lib/Slic3r/Print.pm     | 14 ++++++++++----
 4 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/lib/Slic3r/ExPolygon.pm b/lib/Slic3r/ExPolygon.pm
index 7abaf6b48..89b71324e 100644
--- a/lib/Slic3r/ExPolygon.pm
+++ b/lib/Slic3r/ExPolygon.pm
@@ -51,9 +51,15 @@ sub offset {
     $miterLimit ||= 2;
     
     my $offsets = Math::Clipper::offset($self, $distance, $scale, $joinType, $miterLimit);
+    return @$offsets;
+}
+
+sub offset_ex {
+    my $self = shift;
+    my @offsets = $self->offset(@_);
     
     # apply holes to the right contours
-    return @{ union_ex($offsets) };
+    return @{ union_ex(\@offsets) };
 }
 
 sub encloses_point {
diff --git a/lib/Slic3r/Perimeter.pm b/lib/Slic3r/Perimeter.pm
index bf93315cb..5698ae22c 100644
--- a/lib/Slic3r/Perimeter.pm
+++ b/lib/Slic3r/Perimeter.pm
@@ -42,7 +42,7 @@ sub make_perimeter {
         push @perimeters, [];
         for (my $loop = 0; $loop < $Slic3r::perimeter_offsets; $loop++) {
             # offsetting a polygon can result in one or many offset polygons
-            @last_offsets = map $_->offset(-$distance), @last_offsets;
+            @last_offsets = map $_->offset_ex(-$distance), @last_offsets;
             push @{ $perimeters[-1] }, [@last_offsets];
             
             # offset distance for inner loops
@@ -54,7 +54,7 @@ sub make_perimeter {
             $distance -= $Slic3r::flow_width * $Slic3r::perimeter_infill_overlap_ratio / $Slic3r::resolution;
             my @fill_surfaces = map Slic3r::Surface->cast_from_expolygon
                 ($_, surface_type => $surface->surface_type),
-                map $_->offset(-$distance), @last_offsets;
+                map $_->offset_ex(-$distance), @last_offsets;
             
             push @{ $layer->fill_surfaces }, [@fill_surfaces] if @fill_surfaces;
         }
diff --git a/lib/Slic3r/Polygon.pm b/lib/Slic3r/Polygon.pm
index 47e8ce51d..3d0224dd5 100644
--- a/lib/Slic3r/Polygon.pm
+++ b/lib/Slic3r/Polygon.pm
@@ -65,4 +65,9 @@ sub rotate {
     @$self = rotate_points($angle, $center, @$self);
 }
 
+sub area {
+    my $self = shift;
+    return Slic3r::Geometry::Clipper::area($self);
+}
+
 1;
\ No newline at end of file
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index f87e95488..95f00f0f4 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -2,7 +2,7 @@ package Slic3r::Print;
 use Moo;
 
 use Math::ConvexHull 1.0.4 qw(convex_hull);
-use Slic3r::Geometry qw(X Y);
+use Slic3r::Geometry qw(X Y PI);
 use Slic3r::Geometry::Clipper qw(explode_expolygons safety_offset diff_ex intersection_ex
     offset JT_ROUND JT_MITER);
 use XXX;
@@ -101,8 +101,14 @@ sub detect_surfaces_type {
         # find top surfaces (difference between current surfaces
         # of current layer and upper one)
         if ($upper_layer) {
-            # offset upper layer surfaces by extrusion_width * perimeters
-            @top = $surface_difference->($layer->surfaces, $upper_layer->surfaces, 'top');
+            # only consider those upper surfaces that are not small
+            # (if they're too small, the interface with them can be treated
+            # like a continuous solid surface instead of cutting a little
+            # internal surface in it)
+            my $min_area = ((7 * $Slic3r::flow_width / $Slic3r::resolution)**2) * PI;
+            my $upper_surfaces = [ grep { $_->expolygon->contour->area > $min_area } @{$upper_layer->surfaces} ];
+            
+            @top = $surface_difference->($layer->surfaces, $upper_surfaces, 'top');
         } else {
             # if no upper layer, all surfaces of this one are solid
             @top = @{$layer->surfaces};
@@ -195,7 +201,7 @@ sub discover_horizontal_shells {
                 Slic3r::debugf "  looking for neighbors on layer %d...\n", $n;
                 
                 foreach my $surfaces (@{$self->layers->[$n]->fill_surfaces}) {
-                    my $neighbor_polygons = [ map $_->p, grep $_->surface_type =~ /internal/, @$surfaces ];
+                    my $neighbor_polygons = [ map $_->p, grep $_->surface_type eq 'internal', @$surfaces ];
                     
                     # find intersection between @surfaces and current layer's surfaces
                     # intersections have contours and holes