I have a character rigged and animated using the puppet tool. She will appear in a circular inset and interact with a second character - this I will do by simply creating the circle and using it as a mask for the character.
However, I want her to be able to reach "out" of the inset to take something from the second character. This requires her arms to "break" the mask and reach outside the boundary of the circle. How can I do that short of animating a mask frame-by-frame? Masking/matting of any sort doesn't cooperate with the puppet tool because it masks to the initial rest position of the puppet layers, not the positions after manipulating the puppet pins. - I am no rigging expert, so this may be a fault in my setup.
I would finish my animation of the shot without masking the puppet in the circular inset at all. Just position it on top of the circular inset and animate. I would then render a pass of just the puppet with an alpha, bring that in on top of the original comp, make visible all layers below the puppet and turn visibility off for the puppet layer/layers. Now you can mask the rendered puppet only layer to appear in the circular inset but extend the mask part where the hand reaches "over".