Re: Ignoring texture alpha

 
If your graphics card supports the GL_ARB_texture_env_combine  extension or 
OpenGL 1.3, then you can specify separate texture functions for RGB  and Alpha. 
 Here's an example using...
 
 
// Set the texture environment mode to  ARB_texture_env_combine.
glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,  GL_COMBINE);
 
// Set the texture environment combiner properties for the
// RGB color  channels.
glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB,  GL_MODULATE);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE0_RGB,  GL_PRIMARY_COLOR);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE1_RGB,  GL_TEXTURE);

// Set the texture environment combiner properties for the
// alpha  channel.
glTexEnvi(GL_TEXTURE_ENV, GL_COMBINE_ALPHA,  GL_REPLACE);
glTexEnvi(GL_TEXTURE_ENV, GL_SOURCE0_ALPHA,  GL_PRIMARY_COLOR);


Hope this helps,
Damin.
 
 
In a message dated 3/10/2005 3:49:30 AM Central Standard Time,  
[email protected] writes:

Hi,
I have a texture which is of the format GL_RGBA  and there is
information in the alpha channel. The problem is that I want  to ignore
the alpha channel when drawing, but still use vertex  colour/alpha. I
can't seem to find any way to do this via the texture  functions. At the
moment I'm using GL_MODULATE but I get C=CfCt and A=AfAt,  but I want
C=CfCt and A=Af. I can't change the texture to GL_RGB as I  actually
render it using the alpha channel in other places.

Any  ideas?

cheers,
Bill.