Is there a way to actually discard fragments computation?

[divide]

hello

I was wondering if there is a way with current hardware (let say, my geforce fx) to actually discard computation of some pixels during the fragment process ?
I’m not even talking about the “discard” instruction because it doesn’t actually prevent (from what I’ve heard) the fragment computation, but just cancel the result in the end.

Is there however a trick to discard computation of some fragment shader ?
For example, a first quick pass could “mark” (zbuffer, alpha, … ?) some pixels so they would not be rendered by a second pass.

Do you know if this is possible ?

[zed]

see my recent post/s here, but no with a geforcefx theres no early out in the shaders, u have to use the normal stuff like depthtesting/alphatest which maybe performed before the shader (if the shader doesnt alter anything relavent eg using gl_FragDepth rules out early depthtesting )

[system]

Is there however a trick to discard computation of some fragment shader ?
For example, a first quick pass could “mark” (zbuffer, alpha, … ?) some pixels so they would not be rendered by a second pass.
You mean like the stencil buffer?

Or you can do use the depth buffer by setting it to 0.0 if you have depthfunc = GL_LESS or GL_LEQUAL in the shader. Of course, this will cost you.

[divide]

Allright I’ll try with a depth test, hoping that my geforce will actually do this test before proceeding to the fragment computation.