Simple Tex Env configuration

OpenGL OpenGL: Basic Coding
1

Hi all;
Im implementing a glow fx (like in Tron), and i have to multiply RGB*alpha to get the glow sources visible…how do i configure the tex env combiners to do that?

2

Look up the ARB_texture_env_combine extension. You want both GL_SOURCE(0|1)_RGB to be GL_TEXTURE, but one is taken from the color channels and one from the alpha channel, which is done via GL_OPERAND(0|1)_RGB.

edit: Assuming, of course, that RGB and A is comming from the same texture.

3

Thanx! its working now…another question: how do i blur the texture, to blend with the final image? assume that im doing that by ARB, and to work with radeon 7500+ and geforce2+…

4

How do you mean “blur the texture”? Setting mini-/magnification filter to GL_LINEAR (or GL_LINEAR_MIPMAP_LINEAR if using mipmaps) will blur the texture in some way, or do you want something else?

5

Im trying to do something like this:

  • create a pbuffer, enabling automatic mipmap generation and render to texture;
  • each frame, render the scene to pbuffer, modulating the color (RGB) by the alpha;
  • render the scene to the framebuffer, and draw a quad over the screen with the pbuffer, but or blurred (i dont know how to do that without FS) or with a mipmap level lower than the default, to get almost the same effect .
    The problem now is that i couldnt configure it in the right way, or by creating the pbuffer without the correct parameters, or im not using the tex lod as i should…im setting the min lod and the max lod as the same value, to force the api to use the level i want, but for each level i put in function, the image doesnt change a bit… if somebody already did it, please help me!
6

Its working now…but the quality of blur its not so good…did anyboy tried some configuration, like size of texture N->mipmap level M, that works fine?