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Pentagram
03-01-2003, 12:48 AM
I have a very full register combiner. I use all 8 general rgb combiners, almost fully. (The 8'th combiner has only one dot used.)
But now I want some more math http://www.opengl.org/discussion_boards/ubb/smile.gif
Basically what I want is the result of those 8 combiner stages transformed by res * 0.5 + 0.5 and store this in the alpha out.
This is easy to do with the color part of the final combiner but not with the alpha portion.
So is there any way to tell opengl to swizzle the color-alpha components after the register combiners (color out is unimportant as only alpha writing is enabled.)
I tried to play a bit with the input/output mappings of the general combiners and can get res * 0.5 but the +0.5 part seems inpossible from what I've got left.

[Edit: I found a solution, by using GL_ONE GL_ONE blending and clearing the alpha channel to 0.5 but is there some option that allows thit without blending => saving a read modify write as it's just a constant]

Charles


[This message has been edited by Pentagram (edited 03-01-2003).]