Is there a way to use one blend function for my color values and another blend function for my alpha values? Obviously regular glBlendFunc() can’t do this. I don’t think register combiners have available the color of the pixel already in the color buffer, do they?
I am willing to use any extensions that might help with this, as my only other option is to render everything twice, and it’s an expensive render 
– Zeno
There is an extension that provides a separate color and alpha blend function, but (to the best of my knowledge) no one implements it.
if you are willing to render twice, you can set the ColorMask one time for rendering the Colorvalues and thew other time for Alpha values
Doesn’t the EXT_texture_env_combine extension let you specify color and alpha blend functions separately? But I guess that will only work if you texture your geometry.
Thanks guys. I got it to work last night by doing what daViper suggested. The performance hit seems negligable 
– Zeno
Originally posted by mcraighead:
There is an extension that provides a separate color and alpha blend function, but (to the best of my knowledge) no one implements it.
GL_EXT_blend_func_separate is implemented in FireGL1/2/3 and Wildcat4110…5110