UE5 performance issue resolved by alt-tab??

[toddhacker]

I have a VR project done in 5.3.2, a couple of small levels, relatively low polygon count basically four walls a skyLight, Sky Atmosphere and few pieces of geometry. In editor I have indication of a performance issue whatsoever, everything works great. However, in packaged game I find that the world isn’t entirely locked down the way it should be. It’s not the stuttering effect of low FPS, but turning your head from side to side in VR you can see the environment tracking with the HMD for a bit. If I let the headset (Valve Index) sit for about 30 seconds - 1 minute then put on the headset , everything is rock solid. Also I found that if I alt-tab off the VR program then immediately alt-tab back in (under 2 seconds) everything is rock solid. Packaged using production lighting, Epic Settings, No Nanite, No Lumen. With the time delay to stabilize, I would have though material or texture streaming issue or potentially lighting. But with not much in the scene it’s really strange, this is by no means anything that “should” need to be streamed. However the alt-tab thing is really strange, because that would seem to indicate its not a streaming issue. This is using OpenXR, desktop VR game, Valve Index. Anyone have any ideas?

[Rectus_SA (Rectus)]

It might be related to this issue: Vr headset tracking lag with packaged version only - #4 by VictorLerp

The fix doesn’t seem to have made it into 5.3.2 from what I can see, so you would need to compile the mainline engine yourself or wait for the next release.

[toddhacker]

Thanks for the heads up, I’ll give that a go to see if there’s any difference between the two.

[toddhacker]

@Rectus_SA, I was able to download and build a source version of 5.2.3 and implement those changes laid out in github. That did indeed correct the issue I was seeing. I verified it against 2 other Launcher versions of 5.2.3 on separate computes using both my test project and a few others. I was seeing the same jitter in the launcher version, but no issues in the source built projects. Thanks again for the heads up.