i am new to 3D-textures, i just started to do some dynamic lighting with it.
Anyway, i started with a normal RGB texture. However since 3D-textures need so much memory, i switched to GL_LUMINANCE as the internal format. This works, but it makes problems with alpha-testing. Suddenly all dark corners get invisible. So the LUMINANCE texture seems not only to modulate the color, but also the alpha-channel, which then makes the pixel invisible due to alpha-testing.
So i´d like to know, if there is an internal format, which does the same, except, that it doesn´t change the alpha-channel.
I tried GL_INTENSITY (found it in the msdn), but that seems not to work at all (or it isn´t intended for such a thing?).
And another question: Is it possible to modulate the texture-color of the second texture unit? I mean, i have a grey-scale texture as a light, but what if i want to have a red light? I mean something like glColor, which modulates the polys, but it should only modulate the texture of the second texture-unit BEFORE that one modulates the poly it gets applied to. I tried glSecondaryColor, but that didn´t work.
Well, i think it should be possible with texture_env_combine, but i don´t know much about that extension.