Re: controlling effects with mattes

you may have outlined this method... but to avoid compositing an object over the top of the footage, here's what i might try:

bring your multipass render with rgb matte into an ae comp (so all the layers are there). create a new comp-sized solid, name it 'red matte' or 'sphere matte', apply set matte (take matte from: 'rgb matte', use for matte: 'red channel'). create an adjustment layer and set it to use the 'sphere matte' as a track matte and add effects as needed.

but as far as using a matte layer within an effect, unless the effect has an option for adding the matte channel with in the effect, then i don't know of an easy way to do so...

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW