I have rotoscoped my film and saved all my alpha mattes to a png image sequence. Now for the effect I want to achieve I need to create a new alpha matte image sequence such that:
Frame 1 is the sane as the original frame 1.
Frame 2 is a stack of the original frames 1 and 2.
frame 3 is a stack of the original frames 1, 2 and 3.
If played back as a movie the new sequence would look like a lengthening streak if you follow what I mean. I can’t figure out how to do this in the compositor nodes and would appreciate the help if someone knows how.
Thanks in advance,