π Multimatte
Multimatte is a script for After Effects that makes a new layer with the combined alpha channels of several other layers. You can download Multimatte here.
Installation
Multimatte runs as a ScriptUI Panel with a button if you install it like this:
Quit After Effects if it is running. Move the file Multimatte.jsxbin to your ScriptUI Panels folder, which is located here:
Windows: Program Files\Adobe\Adobe After Effects (version)\Support Files\Scripts
Mac OS: Applications/Adobe After Effects (version)/Scripts
Launch After Effects and click Window > Multimatte.
You can also run Multimatte straight from the Scripts folder, or from a launcher utility like KBar, and in both those cases itβll just do itβs stuff with no panel.
Usage
Select one or more layers and run the script.
Multimatte uses the Set Matte effect which works best with vector layers - shape and text layers, and .ai layers with their π switch turned on. If any of your selected layers won't play nicely with Set Matte (eg. bitmap layers) you'll be given the option to skip them or fix them by either pre-composing them, or turning on their continuous rasterization switch.
If Multimatte needs to pre-compose a layer, it works just the same as if you selected that layer and clicked on Layer > Pre-compose and then selected Leave all attributes.
When it's done, you new Multimatte layer will be at the top of your timeline. You can rename it and drag it anywhere you like. It'll only work in that comp.
Tips + FAQ
If you're using Multimatte with it's UI Panel (because you installed it in your ScriptUI Panels folder) then you can hold the Option / Alt key to tell the script to turn off the visibility of newly generated Multimatte layers. If you use KBar, you can send the argument visibilityOff to do the same thing.
Version History
1.0 - October 19th 2022
Initial release