joining vertex programs?

Quote:

Original post by Madster how can I apply several vertex programs to a surface in a single pass, and have the results accumulate?

You can't. Only one VP can be enabled at any time. You'll either have to write VPs that handle all things (combine them by hand) or write some parser that puts them together (dynamic creation).

The OpenGL Shading Language (GLSL) supposedly allows shaders to be linked together, although I haven't tried it out personally. [edit: I've tried the GLSL, just not linking multiple vertex/pixel shaders together]

[Edited by - benjamin bunny on June 28, 2004 8:31:33 AM]

Personally, I think it's better just to make two passes, one for lighting, and the other one for textures and other effects.

DarkWIng and benjamin hit the point : you can't do it easily in the vertex program level. You are asking a feature of a high-level programming language, thus you should use Cg or GLSL that will handle all temporaries/registers/etc for you. So you either have to rewrite the program string yourself, or switch to a higher level of shader programming.

Nemesis : multipass should only be used as a last resort since it has the (annoying) ability to "eat" the *unique* blending stage (which is still limited today).

thanks everyone.

Seems we'll be skipping rather quickly to GLSL
(and pray that all compiler bugs are gone by 2.0)