Uniforms and dynamic re-compile problem

I have seen a few snippets of info around that talk about issues with (recent) nVidia drivers causing a significant ‘stall’ when uniforms are updated that effectively alter the code path through the fragment shader.

This is certainly a problem that I am seeing (only on newer drivers), and it has been suggested that the problem is caused by the driver re-compiling the shader beause of ‘optimisations’ that were made at initial compile time.

Is there a way of disabling this? The stall that occurs is killing the realtime of our app.

FYI - the stall occurs only the 1st time a shader is used after a uniform altered that changes the code path.

It is not very practicle for me to re-write the shader so that I do not have this behaviour, and even if it was I do not have any confidence that it would not break in the next release of driver.

Any thoughts would be most welcome!


Ask nvidia.
Then please post their response.

Please poke Nvidia about it. I recently was working with a demo that was running at >200fps on a X1600, and <30 on a 7600GT, due to this very issue.

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