View Full Version : secondary color - alpha channel

04-04-2002, 07:37 AM

I have come to realize that when I do something illegal in a register combiner, the mesh is drawn in white.

When I try to use the alpha channel of the secondary color, the mesh is drawn in white.

I have two non-white textures in tex0 and tex1.
both col0.a and col1.a are zero.
when I use the following register combiner:
spare0 = col0.a * tex0;
spare1 = col1.a * tex0;
out.rgb = spare0 + spare1;
out.a = unsigned_invert(zero); // out.a = 1

The mesh is drawn in white. When I use col0.a instead of col1.a, the mesh is properly drawn in black. It appears as if it is illegal to use the alpha channel of the secondary color. This coincides with the fact that the opengl extension for the secondary color does not provide a call for
a 4 channel color, as in 'glSecondaryColor4fEXT'

Is this correct? IS the secondary alpha off limits?


04-04-2002, 08:14 AM
no glSecondaryColor4f existing except with another ext (on gf3 and 4 i think, and possibly radeon 8500, too.. dunno there..)

if you have this additional ext (look through the new exts from nvidia on theyr page) you should have the possibility to access them, else no way.. (it annoyed me for a long time to not have this alpha.. http://www.opengl.org/discussion_boards/ubb/wink.gif)