4.1.0-beta.22 high GPU usage with empty scene in Oculus Quest VR mode with useMultiView

For some reason empty scene in VR mode with useMultiView gives 60% GPU usage according to OVRMetricsTool when 72 fps is enabled.

    this.engine.vrPresentationAttributes = {
        highRefreshRate: true,
        foveationLevel:  0
    };

For some reason if I set useMultiview to false then I get under 15% GPU usage with empty scene.

Kind regards,
Tommi

https://developer.oculus.com/documentation/oculus-browser/browser-optimize-rendering/

Pinging @RaananW

Can you run a profiler to see where the CPU is used?

What extension do you have enabled? Oculus or plain multiview?

I’ll need to check, but enabling anti alias might increase GPU usage

Hi

I was not aware there is something oculus specific I can enable. What can I try on that front? I just used useMultiview with create default VR experience method. I tried with and without antialias and the difference was in order of 5%. The CPU usage was lower than 15%.

Kind regards,
Tommi

When entering chrome://flags you can enable one of two extensions for multiview - the oculus specific one (which supports anti-aliasing) and the regular multi-view extension, which doesn’t support anti-alias (even if set to true).

GPU should not be so high in any way, but the oculus version will use much more GPU time.

Hi

I am using Oculus Quest (standalone headset). In Quest I use the Oculus Browser and I did not need explicitly set any extensions. According to Oculus the oculus_multiview is the one enabled by default:

https://developer.oculus.com/documentation/oculus-browser/browser-multiview/

I am not sure where the problem is but something odd is happening as the GPU usage is more than twice higher with multiview enabled when expected to be lower.

Kind regards,
Tommi

That’s a new (and blessed) change. Both used to be behind a flag last time i checked…

I did some tests just now (the hill valley VR scene):

  1. Without multiview - 47 FPS, 85% average GPU ® usage
  2. With Oculus Multiview - 40 FPS, 95% GPU Usage
  3. Standard Multiview2 - 58 FPS, 75% GPU utilization. But no antialiasing…

Seems like the oculus multiview is not bringing anything positive to the table. I will dig in and see how we can improve that, it is always possible we are doing something fundamentally wrong.

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Great thank you, every gpu% counts :smiley:

-Tommi

That’s an important life motto :wink:

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Oh wow.

Spent a long time on this (since there is another issue with multiview).
Unless I am missing something, we are using multiviews as they were intended to be used. There is a small issue with texture resizing, which leads to a bit of increase in GPU, but it shouldnt influence that much.

And then I went and tested 03 - VR Presentation WebGL2 with my quest , which is the demo oculus puts on their multiview pages:

  1. No multiview - 18% GPU
  2. Multiview OVR (no antialias) - 26%
  3. Multiview Oculus extension - 32%

Dunno… it seems to me like multiview is a nice idea on paper, but when it comes to the extension implementation, it doesn’t fulfill its potential. It is probably due to the fact that for webvr it requires a workaround, which actually makes it work harder.

Having said that, CPU was lower when multiview were used, which kind’a makes sense - less CPU computations, more GPU computations.

I will keep on checking things and try to optimize it as much as we can, but i believe it is a more fundamental issue with multiview and webvr (which is deprecated).

WebXR should support multiview in a different and better way, I am crossing my fingers that by then we will have much better process optimization in the browser.

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