Framebuffer Write Test

It would be nice if OpenGL had functionality to set a fence and then check if anything has been drawn since the fence has been set.

This would be useful for occlusion culling, especially during multipass rendering.

I don’t know how easy this would be to implement in hardware, though.


You might look at the GL_HP_occlusion_test extension (just do a search
on It’s been implemented on both HP Visualize as well as
3D Labs products (and maybe others). HP is working on a new, improved
version which we will release eventually, which allows for multiple pending
visibility test results.

That’s almost exactly what I’m looking for. Too bad it isn’t used in any consumer class video cards.