the aliasing was caused by a low res picture of the seen being partially transparent but visible over top of the seen, with the right shader, this wont be an issue. if you want to get an example of whats happening, take a picture of the engine running at 1024x768, then another screenshot with it at 640x480, take the second one and put it over the otherone in your favorite image editing program, make it partially transparent, and you'll see the same effect.