A specular map - it determines how shiny or dull a texture is in specific areas using B/W values.
For example, you'd use one for a face, giving the shinier elements (the forehead, the bridge of the nose, the upper cheeks, creases in the lips, etc. ) higher values than the rest of the face to help accentuate the important features that usually reflect the most light, due to oil on the skin.
If you google for specular map you can get some really nice examples, and even some tutorials on how to go about creating one correctly. |