I’m sure this is really easy, but I can’t figure it out or find anything about it online. I masked out a skyline from a still frame in Photoshop using the pen tool because it’s easier than AE’s bezier to me. So, I imported the white mask. How do I get the white mask to actually mask to video? How do I get the video I want to show up in the mask I made in Photoshop?
Probably the easiest is to create a Photoshop document where the skyline is over a transparent background. Make sure you can see the checkerboard. AE will just read the checkerboard as an alpha channel, and you’re done.
Put your skyline picture and the mask are on two different Photoshop layers. Save the document. Import the document into AE as a composition. Put the two layers in the AE comp in which you’re working. Put the white mask layer above the skyline layer. In the skyline layer’s modes panel, set it to read the layer above it (the white mask layer) as an Alpha Matte.
If I had to choose which one of the two options above I’d want in my comp, I’d go with the first. It’s lots easier.