per elalish/manifold#1684

techniques to simplify the mesh and remove thin membrains and invalid
shards.

Author: madhephaestus

src/main/java/com/neuronrobotics/manifold3d/CSGManifold3d.java

@@ -182,8 +182,10 @@ public CSG difference(CSG a, CSG b) throws Throwable {
 		MemorySegment mb = toManifold(b);
 		try {
 			MemorySegment result = manifold.difference(ma, mb);
-			MemorySegment smooth = manifold.simplify(result, 0.001);
+			MemorySegment or = manifold.asOriginal(result);
 			manifold.delete(result);
+			MemorySegment smooth = manifold.simplify(or,0.001);
+			manifold.delete(or);
 			checkResult(smooth);
 			CSG fromManifold = fromManifold(smooth, a.getColor());
 			manifold.delete(smooth);