fix: add opengl drift correction for gpu zones#1394
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Thank you, good catch. I suppose there's two options:
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I don't think you would find any. Making this opt-in should be ok. |
We could switch this over to a glQueryCounter maybe? the drift fix wouldn't be perfect (since it would be delayed at worst to a couple frames?) but could still be better than default? I'll try it out and report back. Otherwise, happy to put the synchronous version behind a opt-in config. You know better than I, would that be best as a compiler flag or is there a better way to handle this config? |
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Compiler flag, like the other existing config options. |
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For anyone else reading this in the future: So yea, I'll go with synchronous but behind a compiler flag. |
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| \subparagraph{Calibrated context} | ||
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| By default, the OpenGL context is uncalibrated: the CPU and GPU clocks are aligned only once, when the context is created, so over long captures the two time domains may drift apart (section~\ref{options} describes correcting this drift manually). Defining \texttt{TRACY\_OPENGL\_AUTO\_CALIBRATION} before including \texttt{TracyOpenGL.hpp} enables periodic recalibration instead: roughly once per second Tracy samples the GPU and CPU clocks together and emits a calibration event, allowing the profiler to track and remove the drift automatically. | ||
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| This is opt-in because OpenGL exposes no atomic CPU+GPU timestamp query (unlike Vulkan's \texttt{VK\_EXT\_calibrated\_timestamps} or Direct3D~12, whose contexts are always calibrated). Recalibration therefore reads the GPU clock with \texttt{glGetInteger64v(GL\_TIMESTAMP)}, which forces a CPU/GPU synchronization (a pipeline stall) each time it runs. Enable it only when the improved long-capture alignment is worth the periodic stall. | ||
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feel free to edit the position/content of this to match y'alls standards - not sure if worth mentioning vulkan here for example.
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just to confirm the alignment was correct I added a glfinish() at the end of my frames, and you can see it line up more or less perfectly: |
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Please also add a line in |
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Fixes #1393
Description
Implements opengl drift correction using the existing api (similar to vulkan and d3d12).
Screenshots
Before
(no clock drift correction applied):
Later:
After:
Later:
AI Disclosure
Implemented via Claude Code, tested by me.