Re: Multiple UV channels?
on 04-13-2005 11:22 AM
Most of the time, I've used the second UV channel for lightmaps. So, in channel 1, we'd have our diffuse, bump, and whatever, which may be tiling quite a bit for environmental stuff. Then in channel 2, we bake out separate lightmaps, which obviously we don't want to tile.
For example, say you've got a brick wall with a car parked in front of it, casting a shadow upon it. The brick tiles on the wall, and the environment is pre-lit, using lots of fancy radiostiy/final gathering/global illumination stuff, which is done in the 3d package. So, we would apply a brick material to the wall, and tile the UVs in channel 1, so that the brick pattern repeats. Then we would set up our advanced lighting solution, so that the car cast the shadow on the wall. Next, we would bake this lighting information out to UV channel 2, which is not tiled. This bakes out as a new lightmap texture. The game engine then uses this map in an additive/luminosity type of blend, so that the wall appears to be illuminated properly. It aligns the textures based on the two different UV sets, with the brick texture repeating, and the light/shadow texture not repeating.
So, you could use different UV channels for lots of stuff like this.