That way you should be able to see how often a vertex shader runs for each vertex.

We see that most of a processing order of the Radeons is done Z-order because atomic operation and fragment execution are synchronous.

However, on GeForce there are asynchronous so we can only see the high level patterns of the fragment executions but I am pretty convince that the underlying execution of the fragments follows a sort of Z-order approach.

But instead of coloring the fragments based on the counter value I first stored them in an integer render target so in a second pass I can watch the rasterization in ‘slow motion’ (videos are online of a quad and a killeroo).

This kind of demo is realy the ‘hello world’ of atomic counters (or even OpenGL 4.2?) 😉

The froggy fragsniffer works on AMD hardware has well and there is no OpenGL drivers issue for that.

However: using the The froggy fragsniffer requires tuning even on NVIDIA and will either produce not visible result or reboot your PC.
It also require WinXP because WinVista+ forbide the OpenGL drivers to directly render to the framebuffer.

On Radeon there is no reboot but we can’t see the expected result from Fragsniffer because AMD drivers render to a texture even on WinXP and then blit to the framebuffer.

http://www.icare3d.org/blog_techno/gpu/the_froggy_fragsniffer.html

It’s old and probably won’t run properly on AMD hardware, due to OGL driver issues.