As shown in the screencap below, I have a seemingly simple issue that I always struggle with in Blender: simply turning a designated area into an alpha region (while also retaining the existing alpha data, too).
The Node setup here is the default setup that you get with the Camera Tracker. I’m just trying to block out a small region where there is a pole. So, I created a separate Render Layer and created a Cube for the pole. Unfortunately, it’s just not working.
So any solutions would be appreciated.