I know this can be done but need a keyword. I would like to create alpha letters on one layer and have a black matte to put behind them.
Sounds wierd but Particle Illusion doesn't handle alpha the same way an NLE would. I just want the letters alpha so the emitter can be revealed through them and the black mask will be used to slide across the letters (from behind) to reveal the letters one-at-a-time (Typewriter effect)
Creating punched-out alpha letters on an alpha background is something I have never done and that's where the process comes in.