GL_SGIX_fog_texture
http://oss.sgi.com/projects/ogl-sample/registry/SGIX/fog_texture.txt
	GL_TEXTURE_FOG_SGIX 0
	GL_FOG_PATCHY_FACTOR_SGIX 0
	GL_FRAGMENT_FOG_SGIX 0
	void glTextureFogSGIX (GLenum pname)