Don't just ignore geometric nodes having zero volume/area - when doing difference/intersection, they tend to turn negative objects into positive ones. Fixes #221

1 files changed, 5 insertions, 2 deletions

diff --git a/src/CGAL_Nef_polyhedron.h b/src/CGAL_Nef_polyhedron.h
index e8c505b..d949a2a 100644
--- a/src/CGAL_Nef_polyhedron.h
+++ b/src/CGAL_Nef_polyhedron.h
@@ -8,12 +8,15 @@
 class CGAL_Nef_polyhedron
 {
 public:
-	CGAL_Nef_polyhedron() : dim(0) {}
+	CGAL_Nef_polyhedron(int dim = 0) : dim(dim) {}
 	CGAL_Nef_polyhedron(CGAL_Nef_polyhedron2 *p);
 	CGAL_Nef_polyhedron(CGAL_Nef_polyhedron3 *p);
 	~CGAL_Nef_polyhedron() {}
 
-	bool empty() const { return (dim == 0 || (!p2 && !p3)); }
+  // Empty means it is a geometric node which has zero area/volume
+	bool isEmpty() const { return (dim > 0 && !p2 && !p3); }
+  // Null means the node doesn't contain any geometry (for whatever reason)
+	bool isNull() const { return !p2 && !p3; }
 	void reset() { dim=0; p2.reset(); p3.reset(); }
 	CGAL_Nef_polyhedron &operator+=(const CGAL_Nef_polyhedron &other);
 	CGAL_Nef_polyhedron &operator*=(const CGAL_Nef_polyhedron &other);