UV values above 1.0

I’m planning to use UV values above 1 as a means of passing extra information to the shader, and I’m wondering whether this would run into any problems - e.g., are UVs clipped by some video cards, or are there other problems that might result? (I wouldn’t think so, but you never know…)

No, uv coordinates are never clipped by any hardware. It’s only a texture setting how the texture is sampled. This is entirely controled by the texture’s wrapmode unless you use a shader that clamps the coordinates. Since you write your own shader it’s up to you to pass the uvs correctly ;).

ps. Unity doesn’t use a real texture matrix for the texture offset / scale parameters. There is a function somewhere in the CG-include file that will apply those parameters to the coordinates (this will of course only work when your shader has those parameters ;))