I am trying to replace the fixed functionality renderer with a glsl shader then improve it with various features.

Up to the point of clipping everything works very well. However, if I try to write to gl_ClipVertex (gl_ModelViewMatrix*gl_Vertex) in the vertex shader to use the enabled clip planes, I get a “vertex attribute count exceeds hardware limits” error message.

I don’t understand what can cause this, I didn’t even define any additional vertex attributes at all. I have a few dozens of uniforms and several varying variables, but that is all.

My OS is WinXP SP2 and my GPU is a 8800GT with the latest nVidia driver.

Thanks for your help.