[Keith Neuendorff]

The approach given by Edu does work. To give a bit more detail, I had an existing mask from one frame in the clip that I wanted to apply the mask to but the motion in the clip required that I adjust the mask to match the motion.

I created a new NULL object. I then went back to my main clip and tracked the corner of an object and then applied the tracking data to the NULL object.

I next created a black SOLID and then copied the original mask to that solid and made it SUBTRACTIVE. I then made the NULL the parent of the solid. I mute the solid because we don’t need to see it (we will just use it as a matte). I moved the mask on the solid to overlay the correct point on the original clip that was tracked. At this point I can scrub through the composition and see that the mask is following the original clip correctly. Please note that you should make the dimensions of the solid larger than the composition so that the solid can be used as a matte that won’t move too far over and expose a part that should be masked.

I moved the solid to be in the track list above the original clip. I changed the matte in the original clip to be an alpha matte using the solid. The lower layers now show through on the masked section.

Keith Neuendorff
Tiny Robot Media
Austin, TX

[Keith Neuendorff]

On a somewhat related note…

Using the import (as suggested in one of the above referenced tutorials) is a good way to move Compositions between projects to make them “behave” better and not cause AE to crash.

My specific case was that I had a project that kept getting more complex and ended up where it would not open successfully on my laptop (a decent Core2 Duo Windows machine but with only 3Gig of RAM). To fix this I opened AE with no initial project and did an import on the project that would not normally open. AE complained a bit with some popups but did succeed in opening the project. I cleared out about half of the compositions and media, saved the project under a new name. I repeated this to recover the other half of the compositions and now all of the projects work nicely again.

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One nice additional tip is that if you start deleting compositions from an imported project, I suggest clearing out the Render Queue because AE complains and then sometimes crashes the next time it tries to open the project when it finds references to previoiusly rendered items in the Render Queue that no longer exist in the Project.

Keith Neuendorff
Tiny Robot Media
Austin, TX