Ok, so after reading the appropriate section of the Red Book I now think I understand how the GL_BLEND texture function works and now I find myself asking what it’s good for. I figure this means that I either a) am just plain wrong about how it works, which is why I don’t understand when to use it or b) really just don’t know when to use it
It turns out that GL_MODULATE does what I expeded GL_BLEND to do, and GL_BLEND (if the internal format of the texture is GL_RGB) computes each color as C = C_fragment * (1 - C_texture) + C_envcolor * C_texture according to my copy of the Red Book. What I don’t get is why the (1 - C_texture)?!? I mean, all this seems to do is give me negatives of my textures, which I’m having a tricky time figuring out how or why to use.
The situation doesn’t seem to be any better when using GL_BLEND with any of the other internal formats, except for GL_ALPHA which seems to make sense (but is also identical to the behaviour using GL_ALPHA and GL_MODULATE).
Maybe somone could help shed some light on this?