Medd

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.

2) Gradually reveal the video, 'cutting' through with lines.

I've got something close to what I want so far, after having a fiddle with other examples I've tracked down:

1) Have a white mask cover a video input 

2) Gradually reveal the video, 'cutting' through with lines. 

replaceable-white-mask

If I understand correctly what you want, you could just make a jit.lcd with a white background, draw into it with black lines, and add that to your video. All the pixels that are white (255 255 255) in your jit.lcd matrix will be white in the summed output, and all the pixels that are black (0 0 0) in the jit.lcd will not affect the video.

Excellent! That's just what I was after. Thanks for your guidance.

Replaceable, white mask