Additive blending problem with ppl

OpenGL OpenGL: Advanced Coding
1

I am trying to add the contributions of two lights. What happens though is that nothing gets blend and I only see the result of one or the other. I actually get depth fighting, which really weird since and always use the same calls and matrices to do the transform.

I render all my scene to the depth buffer first, then disable depth write and use GL_EQUAL for depth test and go on with rendering the lighted objects.

I do diffuse by rendering N dot L in the alpha buffer and simply blending with the diffuse color.

This is the setup for a light shining on an object

glColorMask( false, false ,false, true );
{
   glActiveTextureARB(GL_TEXTURE0_ARB);
   glEnable(GL_TEXTURE_CUBE_MAP_ARB);
            
    glBindTexture( GL_TEXTURE_CUBE_MAP,   cubemaptexture) ;

    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
} 

{
    glActiveTextureARB(GL_TEXTURE1_ARB);
    glEnable(GL_TEXTURE_2D);
    

     glBindTexture( GL_TEXTURE_2D, bumpMap );

    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE_ARB);
    glTexEnvf(GL_TEXTURE_ENV, GL_COMBINE_RGB_ARB, GL_DOT3_RGBA_ARB);
    glTexEnvf(GL_TEXTURE_ENV, GL_SOURCE0_RGB_ARB, GL_PREVIOUS_ARB);
    glTexEnvf(GL_TEXTURE_ENV, GL_OPERAND0_RGB_ARB, GL_SRC_COLOR);

    glTexEnvf(GL_TEXTURE_ENV, GL_SOURCE1_RGB_ARB, GL_TEXTURE);
    glTexEnvf(GL_TEXTURE_ENV, GL_OPERAND1_RGB_ARB, GL_SRC_COLOR);

}  

Draw();

{
glDisable(GL_TEXTURE_2D);

 glActiveTextureARB(GL_TEXTURE0_ARB);
  glDisable(GL_TEXTURE_CUBE_MAP);
}

//do the color pass

glEnable(GL_BLEND);
glBlendFunc(GL_DST_ALPHA,GL_ONE);

glColorMask( true, true , true, false );
{
    glEnable(GL_TEXTURE_2D);


    glBindTexture( GL_TEXTURE_2D, diffuse ) ;

    glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
} 

Draw();

glDisable(GL_TEXTURE_2D);
glDisable(GL_BLEND);

Blending does work properly when I am rendering differently.

If somebody could point something wrong or hint on something to look for, I would be quite happy.

[This message has been edited by Gorg (edited 02-04-2003).]

[This message has been edited by Gorg (edited 02-04-2003).]

2

instead of using destination alpha

why cant u just enable blending with ONE ONE for each extra light (turn off zwrites as well for a performance boost)

3

I am using a normalisation cube map, and I am restricted to 2 tex units. So I need at least 2 passes, I don’t think I can set that up with ONE, ONE ?

4

i like to do all the lights first (which could be many using ONE ONE) + then last of all draw the decal texture with blending DST_COLOR ZERO

5

I see. That could be problematic has the architecture is working per light/object. Though I will still try to try it to see if I can at least get the blending to work properly.

Though I still assume my code should work. I guess you could not point anything obvious from the source?