I’m a bit confused. I remembered looking at one Logik live but forgot which one.
In this episode, He/Her shows us how to connect the matte viewer to the camera to see and modify our alpha connected to the motion vector pass.
Does someone remember which live it was or can show me the schematic?
Forgive me Im not at my machine right now, but see if the Matchbox shader SelectiveMatteExtraction in the root of your /shaders directory is the one you are after.