UE4 to UE5 VR Performance Drop

Development Platform & Builds XR Development
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Hi all, I have recently moved a project from Unreal Engine 4 to Unreal Engine 5 (5.4), and after upgrading, we have seen pretty significant performance drops. I’m not sure if it is a factor, but the project is quite old. It was originally started in 4.19 and has been updated over the years through the different versions of Unreal Engine 4. It was on 4.27 in August 2023 when we decided to upgrade to 5.2, and then, to catch the recent improvements to the Open XR plugin, we took it into 5.4.

When packaging, we have noticed a pretty significant performance drop. In most levels, this drop is typically about 2-4 ms, but it has been as much as 15 ms in some levels when compared to our last build from UE4. With a target of 11ms a frame, these additional milliseconds are consistently preventing us from hitting our performance goals. We have tried a wide variety of different things to improve the performance, but we have not been able to meet our targets on all levels. It seems like in order for things to run properly we have to put the player in a nearly empty level.

The improvements that we have tried include but are not limited to the following:

  • Taking all steps recommended by the VR best practices guide
  • Removing Virtual Shadow Maps
  • Disabling Virtual Textures
  • Disabling Nanite
  • Disabling Lumen
  • Turning off many lighting features, such as CSM shadows
  • Converting all duplicated Static Mesh Actors to Hierarchical Instanced Static Meshes

I would love to hear if anyone has been experiencing anything similar and if anyone has any additional recommendations for improving VR performance.

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This is what I’ve found too, and I’m confused by people reporting they notice no difference in performance. To us it’s prevented us from being able to migrate to UE5, if you do come up with something I’d love to hear it as it’s really unfortunate not to be able to use some of the quality of life features and new plugins / content.

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Hi,

had the same issue with our 4.27 flight sim when moving first to UE 5.2. The rock-solid 90 fps with CESIUM full world rendering for the Varjo XR-3 were gone, we were constantly above 11ms.

Now we’re down to 45 fps, and I don’t like that too much, but the flying is still good and I now make use of volumetric clouds, weather effects, even rendering now Google Photogrammetry 3DTiles for rendering the world. And that looks really good for VFR flying.

I’m now moving the project to 5.4, and maybe with the improvements to the rendering we might be able to go for 90fps again, with the fastest CPU and the RTX 4090s that we are using.

Best
Andreas