Hi All,
I have a scene with a few (~10) simple objects and 2 light sources. Under specific conditions I observe a sudden one frame stall. Then it returns back to normal and never happens again until I restart the application.
[ol]
[li]My application loads the scene and constantly renders it on the screen (sleep is not called)[/li][li]The scene is static (no animations, particles, etc.)[/li][li]So far the FPS is pretty much constant with each frame taking ~15 ms to render (vsynch is off)[/li][li]When the camera starts rotating a stall occurs with one frame taking ~65 ms to render[/li][li]After this moment the issue never happens again under any circumstances.[/li][/ol]
[ATTACH=CONFIG]472[/ATTACH]
On the left there is a performance graph, showing the stall. On the right there are two screenshots taken before and right after the stall occurred. As you can see nothing changes except the camera slightly rotates.
Can anyone explain what is going on there? Maybe somebody has a similar experience?
Several more facts
[ol]
[li]The issue is 100% consistent[/li][li]The magnitude of the rotation angle which triggers the issue is constant for each initial camera orientation, but it varies between different initial orientations.[/li][li]It happens only when I have at least one light source in the scene.[/li][li]When I switch light sources in the scene off, I encounter similar stalls. This makes me think that’s the FFP emulator recompiles its shaders, but what would be the reason to recompile shaders just because the camera rotates? [/li][/ol]
Application information:
[ul]
[li]OpenGL 2.1 FFP with occasional use of shaders (in this particular example shaders are not used)[/li][/ul]
The issue presents on all the AMD platforms I have managed to find:
[ul]
[li]AMD Radeon HD 6800 \ Windows 7 \ Driver 9.12 (Catalyst 13.1)[/li][li]AMD Radeon HD 6670 \ Windows 7 \ Driver 9.12[/li][li]AMD Radeon HD 6320 \ Linux \ [/li][li]ATI Technologies Inc Radeon E2400 \ Linux \ [/li][/ul]
The issue does not occur on all the NV platforms I have managed to find:
[ul]
[li]NVIDIA GeForce GTX 460M \ Windows 7 \ Driver 8.17.12.9616[/li][li]NVIDIA Quadro FX 880M \ Windows 7 \ Driver 9.18.13.1106[/li][/ul]
It would be great if there was a way to avoid the stalls, but I doubt it. So I’m just trying to understand this phenomena. I would appreciate any related information.
Thanks,
gonzaless