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3d tracking and moving mask
I have what may be a dumb question. But I am struggling to find the right answer.
I have used syntheyes to track a sequence. I have imported to after effects. Objects are placed and scaled properly when the items ( images) are placed in 3d space. They track properly.
What I want to do: Mask out a portion of the 2D footage I tracked in syntheys and attach the mask to a null in 3d space which is parented to a image I want to use for a set extension/matt painting. (Imagine castle on horizon line of tracked footage).
My problem: I cannot figure out how to mask the 2d footage and use the tracking data to make the mask move AND MASK MY FOOTAGE.
The only way I can figure out to mask the footage is by drawing a mask on the original footage. I can’t make a mask drawn say on a null or adjustment layer affect the tracked 2d footage.
Problem seems to exist with 3d layer perspective and 2d layer masking.
Help please.
Thanks,
John