I haven't been able to figure out a way to do this, but my inkscape skills aren't too strong. I have a drawing that at the lowest level has an irregular glow. It's a freehand path-based polygon with a heavy blur on it. The blur is all alpha. On top of this is path-based, alpha=1 object; nothing special. I need to knockout an interior region of this to an alpha of zero. It's easy to knockout the alpha=1 object with path difference. However, I can't figure out how to cut a hole in the underlying glow-producing path. It's easy enough to do the path difference, but this actually cuts a hole in the glow-producing path which then blurs into the interior, the part I want to be alpha=0. What I'd like to do is kinda multiply the alpha channel of two paths/groups. The (incorrect) approximation of this is to take the png that I produce at the end and map a particular color to the alpha channel. This doesn't handle the anti-aliased edges correctly. Any suggestions?