First off, apologies for my lack of Jitter fluency. I've not ventured into it much, although more and more I'm calling upon the objects to work with some of my Max/MSP projects.
What I'm trying to do is:
1) Have a white mask cover a video input
2) Gradually reveal the video, 'cutting' through with lines.
3) Cover the video with white again.
I've got something close to what I want so far, after having a fiddle with other examples I've tracked down: