was an experimental shader in Unreal 3. Basicly we were doing per-pixel
uv scrolling on a particle system. In terms of instruction count
and texture usage, it's very cheap. Fill rate isn't that bad, either.
But in terms of texture fetching, it's very, very expensive. We
got this up and going at about 40-50 fps on an xbox 360, but this
assumes you aren't loading a bunch of other textures. Interesting,
but not entirely useful for the game I was working on.