Shadows and CG (bug)

I checked out the shadow demo and I saw that it uses a CG shader. The demo seemed to work on my machine (if I was supposed to see a gridlike shadow on the teapot/panda), although I use an ATI card (HD 3800). (If I stop the teapot rotation but keep the Panda marching, I will see the shadow vibrating on the teapot at certain positions of the panda; if I stop the panda as well, the vibrations stop too.)

What I don’t understand is:
1, If these shaders are in CG, how is that the demo still works for me (although little buggy).
2, Isn’t shadow casting a standard feature for videocards? Why is there a need for shaders?

I never programmed shaders, and have only a superficial knowledge about them.

Why wouldn’t it? I assume your card supports Cg shaders…

It’s a common misconception that Cg does not work on ATI cards. Cg should work on any card that supports shaders.

It’s a standard feature (also see the shaderless shadow example I posted somewhere here at the forums) through the ARB_shadow extension, but some drivers/cards (especially ATI) seem to have a buggy implementation of it.

I thought ATI cards only support GLSL and HLSL, but thanks for correcting me.

Btw. can you give an explanation, why the panda’s movement affects the shadow on the teapot? Or is this a bug?

What do you mean? They move independently.

This is what happens when I stop the teapot rotation but keep the panda rotating:

Btw. what is push bias?

Compared with the image in the manual, it definitely looks like a bug. … s:_Shadows