I'm trying to render a model that has 10+ layered textures. At the moment, my implementation uses blending exclusively to accomplish this. Blending in this way is very powerful since the user who creates the model can specify a different combination of blending parameters for each texture layer (by default it is additive as (GL_ONE, GL_ONE), but could be any of the legal blending methods). The resulting speed, of course, from all this blending is not so good, so I am trying to incorporate multitexturing into the procedure. I am finding though that the color mixing process is quite different. I can simulate additive blending with the texture operation GL_ADD, but many of the more complex blending combinations do not seem to have a multitexturing equivalent. Are there any good ways to deal with this?