Dramatic drop in fps with UE4.26 + SteamVR

[Rectus_SA (Rectus)]

Have you profiled the application to see what is eating up the performance? Is it GPU or CPU bound?

Also note that VR runtimes will throttle the application down to fractions of the framerate when it fails to meet the target, so measuring the frame time in ms is much more useful than measuring FPS. If your application fails to meet 80 FPS it will show 40 regardless of the actual performance.

I have an constant issue with the render thread blocking and breaking frame sync when using 4.26 with the SteamVR plugin, and I’m wondering if it would be the same thing causing it.

Frame Timing issues with SteamVR

I’m experiencing consistently occurring frame timing issues when using SteamVR. Every now and then the render thread will start blocking for several milliseconds waiting for RenderQuery results. This causes the app to miss the SteamVR running start frame synchronization and can easily cause periodical dropped frames. Missing the running start seems to also cause additional issues with jitter and increased reprojection artifacts. The frequency of the frame blocking seems to vary with performance…