our engine uses "cosine" maps which are pretty much gloss maps, except they take specular intensity and glossiness into account. so instead of dealing with 2 maps, you only deal with 1.
not really. gloss and roughness maps perform the same function to the artist. but the way they are calculated internally are both very different. and, more to the point. roughness has a finite value, whereas gloss doesn't. for example, gloss maps allow you to input a value between 0 and 1. this is then interpolated to…
that's because if you take the value over one, you start getting lighting artifacts, because the light diffuses further than is physically possible. another way to look at it, is the angle at which light can be seen to reflect from the surface, which does go to a limited value. http://en.wikipedia.org/wiki/Glossmeter so…