New algorithm for clipping lines to complex polygons

lib/Slic3r/Geometry.pm

@@ -90,9 +90,7 @@ sub point_in_polygon {
     
     # if point is not in polygon, let's check whether it belongs to the contour
     if (!$side && 0) {
-        foreach my $line (polygon_lines($polygon)) {
+        return 1 if polygon_segment_having_point($polygon, $point);
-            return 1 if point_in_segment($point, $line);
-        }
     }
     
     return $side;
@@ -458,5 +456,22 @@ sub bounding_box_intersect {
     return 1;
 }
 
+sub clip_segment_complex_polygon {
+    my ($line, $polygons) = @_;
+    
+    my @intersections = grep $_, map line_intersection($line, $_, 1), 
+        map polygon_lines($_), @$polygons;
+    
+    @intersections = sort { "$a->[X],$a->[Y]" cmp "$b->[X],$b->[Y]" } @intersections;
+    
+    shift(@intersections) if !grep(point_in_polygon($intersections[0], $_), @$polygons)
+        && !grep(polygon_segment_having_point($_, $intersections[0]), @$polygons);
+    
+    my @lines = ();
+    while (@intersections) {
+        push @lines, [ shift(@intersections), shift(@intersections) ];
+    }
+    return [@lines];
+}
 
 1;

t/geometry.t

@@ -2,7 +2,7 @@ use Test::More;
 use strict;
 use warnings;
 
-plan tests => 4;
+plan tests => 5;
 
 BEGIN {
     use FindBin;
@@ -13,8 +13,14 @@ use Slic3r;
 
 #==========================================================
 
-my $line1 = [ [73.6310778185108/0.0000001, 371.74239268924/0.0000001], [73.6310778185108/0.0000001, 501.74239268924/0.0000001] ];
+my $line1 = [ [5, 15], [30, 15] ];
-my $line2 = [ [75/0.0000001, 437.9853/0.0000001], [62.7484/0.0000001, 440.4223/0.0000001] ];
+my $line2 = [ [10, 20], [10, 10] ];
+is_deeply Slic3r::Geometry::line_intersection($line1, $line2, 1), [10, 15], 'line_intersection';
+
+#==========================================================
+
+$line1 = [ [73.6310778185108/0.0000001, 371.74239268924/0.0000001], [73.6310778185108/0.0000001, 501.74239268924/0.0000001] ];
+$line2 = [ [75/0.0000001, 437.9853/0.0000001], [62.7484/0.0000001, 440.4223/0.0000001] ];
 isnt Slic3r::Geometry::line_intersection($line1, $line2, 1), undef, 'line_intersection';
 
 #==========================================================

t/polyclip.t

@@ -1,6 +1,6 @@
 use Test::More;
 
-plan tests => 9;
+plan tests => 10;
 
 BEGIN {
     use FindBin;
@@ -9,7 +9,7 @@ BEGIN {
 
 use Slic3r;
 
-my $square = [
+my $square = [  # ccw
     [10, 10],
     [20, 10],
     [20, 20],
@@ -21,18 +21,42 @@ my $line = [ [5, 15], [30, 15] ];
 my $intersection = Slic3r::Geometry::clip_segment_polygon($line, $square);
 is_deeply $intersection, [ [10, 15], [20, 15] ], 'line is clipped to square';
 
+#==========================================================
+
 $intersection = Slic3r::Geometry::clip_segment_polygon([ [0, 15], [8, 15] ], $square);
 is $intersection, undef, 'external lines are ignored 1';
 
+#==========================================================
+
 $intersection = Slic3r::Geometry::clip_segment_polygon([ [30, 15], [40, 15] ], $square);
 is $intersection, undef, 'external lines are ignored 2';
 
+#==========================================================
+
 $intersection = Slic3r::Geometry::clip_segment_polygon([ [12, 12], [18, 16] ], $square);
 is_deeply $intersection, [ [12, 12], [18, 16] ], 'internal lines are preserved';
 
+#==========================================================
+
+my $hole_in_square = [  # cw
+    [14, 14],
+    [14, 16],
+    [16, 16],
+    [16, 14],
+];
+my $intersections = Slic3r::Geometry::clip_segment_complex_polygon($line, [ $square, $hole_in_square ]);
+is_deeply $intersections, [
+    [ [10, 15], [14, 15] ],
+    [ [16, 15], [20, 15] ],
+], 'line is clipped to square with hole';
+
+#==========================================================
+
 is Slic3r::Geometry::point_in_segment([10, 10], [ [5, 10], [20, 10] ]), 1, 'point in horizontal segment';
 is Slic3r::Geometry::point_in_segment([30, 10], [ [5, 10], [20, 10] ]), 0, 'point not in horizontal segment';
 is Slic3r::Geometry::point_in_segment([10, 10], [ [10, 5], [10, 20] ]), 1, 'point in vertical segment';
 is Slic3r::Geometry::point_in_segment([10, 30], [ [10, 5], [10, 20] ]), 0, 'point not in vertical segment';
 is Slic3r::Geometry::point_in_segment([15, 15], [ [10, 10], [20, 20] ]), 1, 'point in diagonal segment';
 is Slic3r::Geometry::point_in_segment([20, 15], [ [10, 10], [20, 20] ]), 0, 'point not in diagonal segment';
+
+#==========================================================