So I made a little example project and I think that if you know illustrator you could probably make your shapes a little quicker and accurately. I don't know illustrator well enough to do that, so I just made my masks in AE the best I could, but you should get the idea of how to do this by looking at my project.
6321_triangles.aep.zip
Johnny Cuevas, Editor
Thinkck.com
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.