I'm using the compositor to automatically segment parts of objects into masks. This works well for most materials, but when doing the same for a mix shader of glossy and transparent it doesn't, how to fix this?
On a sidenode: The same thing happens when I use materialIDs.
The file is too big for the official uploader; I hope dropbox doesn't deter you. https://www.dropbox.com/s/alv6jq6vnvshgzs/stack.blend?dl=0
You'll have to set the output path and should then be able to reproduce by pressing render.