i wanted to do a level with a matrix style code scrolling across the texture(but where the black is alpha'ed), but i cant figure out how to make the texture black(alphad afterwards) if you paint black onto it it has no effect. any ideas?
If you're creating the textures in code then you can just go over the texture with ReadPixel and WritePixel, and write 0 alpha for all pixels which are black. Far too slow to do it on the fly, but you only need to draw the texture once, then you can just scroll the texture over the mesh to make it move.