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SlateUI crippling my games' performance, only in VR.

FredrumFredrum Posts: 170
edited August 11 in Unreal


I am currently spending some time looking at my games' performance and optimizing both cpu and gpu based areas.
One thing that is currently driving me crazy is this SlateUI item from the GPU profiler output.

I am testing this with a packaged/cooked version of my Unreal game. I am not using any slatey 2d ui things.
When I test the same build in 2d desktop mode I don't even get a SlateUI item in the list.

It seems to just happen when rendering to the Rift.

Here's an example output,
[2017.08.11-23.18.47:140][391]LogRHI: 38.1% 3.86ms   SlateUI 1 draws 2 prims 4 verts

So since it seems to be VR only related I was hoping someone here know what causes this and how I can get rid of it.
It's way too many ms from the 11ms budget.



  • FredrumFredrum Posts: 170
    edited August 14

    I would love to get the thought of someone at Oculus about this one.

    After testing some more it seems like this is tied to the mirroring window output.

    I created a new Unreal default VR blueprint project. Didn't change anything except a toggle to turn on and off vr mirroring with a blueprint command 'vr.spectatorScreenMode 0'.
    I then ran the same cooked build eight times, alternating the on/off state of the vr mirroring output window, and getting a unreal editor GPU profiling output dump to the log file using Shift+Ctrl+comma.
    I restarted the game inbetween each take, ie 8 times.

    This is what I got and you can clearly see that the mirrored runs consistently get an ~3ms penalty.

    (the runs without mirroring don't get a 'slate ui' item in the profiler output)

    This is the same result as I am seeing with my main game project.
    It's not good as it means that I can't have the mirroring it's just too crazy expensive. I don't see why it even should be it should just be using already an rendered image and displaying that in a window.


  • imperativityimperativity Posts: 1,172 Oculus Staff

    I am currently looking into this and will advise you on what information I find that is applicable to your situation.

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