specular map normal map gloss map

http://www.marmoset.co/toolbag/learn/materials

http://digitalerr0r.wordpress.com/2009/03/26/xna-shader-programming-tutorial-8-gloss-map/

对specularmap sample = speSampVal

对glossmap sample = glossSampVal

specularResult = speSampVal * (speFactor)^glossSampVal

specularmap控制光照的颜色强度

glossmap控制反光的范围，决定材质质感