Track Matte (alpha/luminance) on multiple layers
Preferably I would love Groups to do this (being able to add multiple layers to a group thats affected byt he same adjustment or alpha layer), the same way as Photoshop. But being able to select that multiple layers track matte from one source is something I miss a LOT of times and have to find ways to work around the limitations of the program.
David Salustri commented
Rfred - You mentioned you need to duplicate your masking layer every time you want to create another track matte.
You can use an effect to do that instead...
Add Effect > Channel > 'Set Matte'
Then you can choose any layer to be your track matte.
But as far as this thread is concerned, I think the track matte feature should be updated with a pickwhip tool, to choose any layer as my mask.
currently have many layers that all need the same track matte. Each is composited over the others transparently or keyed. They all must be keyed using the alpha from footage. I need to adjust all of their placement/transparency/blending mode, etc. over a background, keyed into an animated mask.
I have not been able to use set alpha to do this because the mask is then tied to the layer and moves with it.
I currently am duplicating the mask layer to be used for the track matte for each of the MANY layers I need to have this matte layer.
Precomp will work but it removes my ability to edit and adjust these layers and see the results over the background and under this mask layer.
Why not have track mattes work like parenting, simply choose the layer for a track matte. Done. The constraint that it be only the layer directly above seems arbitrary and illogical.
pick-whipabble alpha mate preferably, so you dont' need to move your layers
I was literally just writing up this very thing. It's such a waste of time to work around what could be so quick and simple. Pre-comps and using multiple track mattes can get very confusing in the timeline when making adjustments.
Michael Douglas commented
Have you tried using Set Matte? You can then use a single layer as a track matte instead of having multiple copies of your track matte mask layer. It can use the alpha or luminance info of the layer you select. That won't help you for adjustment layers, though.
Select the layers you want to affect in this way and right-click, and select Pre-Compose. Most of the time, this is the solution, and basically works the same way as grouped layers in Photoshop.