To Vertex Shade or not to Vertex Shade

The GLSL specification says that it is legal to create a shader that has one instance of a fragment shader and no vertex shader. Under these conditions, the default vertex pipeline should run. This worked on Nvidia and ATi - sort of. ATi allowed it but did not set up gl_FragCoord correctly - effectively making the fragment shader useless. In other words, it didn't work.

However, on Feb 13th 2008 ATi released new drivers which cured the problem. So its now possible to write tiny glsl code without a vertex shader.

Only tested for sure on x1950 so far but will test on other cards soon...