been having an idea for a little while now, and i just got something together for it.
give a car's wheel a regular flat saturation map, and then a very noisy, high-res, specular map. to get a metallic glow effect.
here's something i came up with for it. the reason why this seemed an appropriate place to put it is that the specular map had to be very high-res 2048x2048. in fact i think it would only really get the right effect if it were even bigger. or i was using the full 2048 for that part of the wheel. i have a feeling this would be a good approach for lots of rims and even pearl coats. but to do this i think there needs to be a general shader library somewhere that can be called for any vehicle or any track object. this way there could be a single tile-able, super high-res noise map that could be used for anything that has glittery highlights. and it would only take up that 12.5MB of texture memory once.
thinking about the tile-able part: if it could be tile-able 3 ways (so each triangle would get the full texture resolution) that would probably be ideal, could maybe get away with a lower res texture too. actually since it's just a noise texture it might be tile-able 3 ways be default, not quite sure.