Moved special handling of intersection to ClipperUtils

src/GeometryEvaluator.cc

@@ -367,26 +367,7 @@ Polygon2d *GeometryEvaluator::applyToChildren2D(const AbstractNode &node, OpenSC
 		break;
 	}
 
-	if (clipType == ClipperLib::ctIntersection && !children.empty()) {
-		// intersection operations must be split into a sequence of binary operations
-
-		std::vector<const Polygon2d *> operands(2);
-		operands[0] = children[0];
-
-		for (int i = 1; i < children.size(); i++) {
-			operands[1] = children[i];
-			Polygon2d * result = ClipperUtils::apply(operands, clipType);
-			if (operands[0] != children[0]) delete operands[0];
-			operands[0] = result;
-		}
-
-		assert(children.size() >= 2);
-		// We know that this is ok
-		return const_cast<Polygon2d *>(operands[0]);
-	}
-	else {
-		return ClipperUtils::apply(children, clipType);
-	}
+	return ClipperUtils::apply(children, clipType);
 }
 
 /*!

src/clipper-utils.cc

@@ -34,7 +34,13 @@ namespace ClipperUtils {
 		clipper.Execute(ClipperLib::ctUnion, result, ClipperLib::pftEvenOdd);
 		return result;
 	}
-
+	
+ /*!
+	 We want to use a PolyTree to convert to Polygon2d, since only PolyTrees
+	 have an explicit notion of holes.
+	 We could use a Paths structure, but we'd have to check the orientation of each
+	 path before adding it to the Polygon2d.
+ */
 	Polygon2d *toPolygon2d(const ClipperLib::PolyTree &poly) {
 		Polygon2d *result = new Polygon2d;
 		const ClipperLib::PolyNode *node = poly.GetFirst();
@@ -71,6 +77,23 @@ namespace ClipperUtils {
 									 ClipperLib::ClipType clipType)
 	{
 		ClipperLib::Clipper clipper;
+
+		if (clipType == ClipperLib::ctIntersection && pathsvector.size() > 2) {
+			// intersection operations must be split into a sequence of binary operations
+			ClipperLib::Paths source = pathsvector[0];
+			ClipperLib::PolyTree result;
+			for (int i = 1; i < pathsvector.size(); i++) {
+				clipper.AddPaths(source, ClipperLib::ptSubject, true);
+				clipper.AddPaths(pathsvector[i], ClipperLib::ptClip, true);
+				clipper.Execute(clipType, result, ClipperLib::pftNonZero, ClipperLib::pftNonZero);
+				if (i != pathsvector.size()-1) {
+                    ClipperLib::PolyTreeToPaths(result, source);
+                    clipper.Clear();
+                }
+			}
+			return ClipperUtils::toPolygon2d(result);
+		}
+
 		bool first = true;
 		BOOST_FOREACH(const ClipperLib::Paths &paths, pathsvector) {
 			clipper.AddPaths(paths, first ? ClipperLib::ptSubject : ClipperLib::ptClip, true);

tests/regression/dumptest/intersection2-tests-expected.csg

@@ -0,0 +1,79 @@
+group() {
+	multmatrix([[1, 0, 0, 0], [0, 1, 0, -20], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		intersection() {
+			circle($fn = 0, $fa = 12, $fs = 2, r = 5);
+			square(size = [8, 8], center = true);
+		}
+	}
+	multmatrix([[1, 0, 0, -10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		intersection() {
+			circle($fn = 0, $fa = 12, $fs = 2, r = 5);
+			square(size = [0, 0], center = true);
+		}
+	}
+	multmatrix([[1, 0, 0, 0], [0, 1, 0, 20], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		intersection() {
+			group();
+			circle($fn = 0, $fa = 12, $fs = 2, r = 5);
+			square(size = [8, 8], center = true);
+		}
+	}
+	multmatrix([[1, 0, 0, 20], [0, 1, 0, -20], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		intersection() {
+			multmatrix([[1, 0, 0, 10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+		}
+	}
+	multmatrix([[1, 0, 0, 20], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		intersection() {
+			multmatrix([[1, 0, 0, 10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+			multmatrix([[-0.5, -0.86602540378, 0, 0], [0.86602540378, -0.5, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				multmatrix([[1, 0, 0, 10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+					circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+				}
+			}
+		}
+	}
+	multmatrix([[1, 0, 0, 20], [0, 1, 0, 20], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		intersection() {
+			multmatrix([[1, 0, 0, 10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+			multmatrix([[-0.5, -0.86602540378, 0, 0], [0.86602540378, -0.5, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				multmatrix([[1, 0, 0, 10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+					circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+				}
+			}
+			multmatrix([[-0.5, 0.86602540378, 0, 0], [-0.86602540378, -0.5, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				multmatrix([[1, 0, 0, 10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+					circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+				}
+			}
+		}
+	}
+	multmatrix([[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+		intersection() {
+			multmatrix([[1, 0, 0, 10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+			multmatrix([[1, 0, 0, 5], [0, 1, 0, 8.66025403784], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+			multmatrix([[1, 0, 0, -5], [0, 1, 0, 8.66025403784], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+			multmatrix([[1, 0, 0, -10], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+			multmatrix([[1, 0, 0, -5], [0, 1, 0, -8.66025403784], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+			multmatrix([[1, 0, 0, 5], [0, 1, 0, -8.66025403784], [0, 0, 1, 0], [0, 0, 0, 1]]) {
+				circle($fn = 0, $fa = 12, $fs = 2, r = 15);
+			}
+		}
+	}
+}