PDA

View Full Version : Passing to fixed pipeline



Jaak
04-09-2005, 11:54 AM
Hello,

I have gfx card without fragment shader support, but I`d still like to use vertex shader. There are numerous tutorials around the web, but none tells me what to do if I do *not* want to use fragment shader.
I tryed to attach only a vertex shader, but only thing I get is a black polygons, it is possible that I am doing something very wrong. I did some search, only thing I was able to get was:

If no vertex shader is active, the fixed functionality pipeline of OpenGL will compute values for the builtin varying variables that will be consumed by the fragment shader. Similarly, if no fragment shader is active, the vertex shader is responsible for computing and writing to the varying variables that are needed for OpenGLís fixed functionality fragment pipeline.This can be rather insignifican`t because it`s about varying variables.

so, now the questions:
1) Can I use glsl without fragemnt shaders.
2) and if so, what do i need to output in vertex shader so that fixed pipeline fragemnt shader can take over.
3) or what (if anything) do I need to tell to opengl if I`m not going to use fragment shaders.

...other than that... I think it is time for me to get a proper video card.

Ffelagund
04-10-2005, 12:34 AM
It is perfectly possible use only vertex shaders, without fragment shaders, but you must take care about write the built un varying variables that are needed in later rendering stages, such as texture coordinates (gl_TexCoord[x]), gl_FrontColor, etc. The best place to know wich variables do you need to write is the glsl spec :)

Jaak
04-11-2005, 03:52 AM
Ah, thanks you,

got everything i needed from glsl specs, i honestly got scared, that glsl doesn`t support cards without fragment shaders :)