Compositing alpha problem

Hi!

I have a problem with the set alpha node. What I want to do is mask the black outline of the teapot (alpha png) with the grunge texture. What I expected was to get the outline back but now ‘jagged’ masked. But instead it has now a white background that’s also masked. How ca


Set alpha replaces the alpha channel, it doesn’t combine it. You need to do that ahead of time. Use a math node to multiply your texture with the “alpha” socket from your image, then pass THAT into the set alpha node.