» Sun May 20, 2012 7:54 am
It seems a sort of greyscale mask for environment maps for enhancing/damping the reflective effect on materials. For example, if you have an armor made both of leather and steel, you want reflections only on the metal parts, not on leather least you'll have the shiny plastic effect of Doom III.
I think the result of the cross product of lighting and specular map is then multiplied with this map to modulate the intensity.