Virtual Desktop's SSW feature will freeze my entire game at 45 fps

Virtual Desktop’s SSW feature will freeze my entire game at 45 fps, and the frame rate will return to normal when SSW is turned off. What can I do about this? The Virtual Desktop app for Quest2 is used.

Make sure your game is hitting 90 Hz consistently. Reprojection techniques like SSW require throttling the frame rate in half to work, and the runtime will do that when it detects that the game is missing the frame submission time repeatedly.

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I preview the VR template project for ue4.27 and this happens too. I think the frame rate is adequate.This would be very bad in a game with a predominantly physical presentation.

Is there any hint for missed frames in ue4? I’d like to know which function triggers the SSW to start.

When using Virtual Desktop, the easiest way would be to use the SteamVR frame timing graph from SteamVR Window->Menu->Developer->Advanced Frame Timing.

You can also capture a trace with the UE4 profiler:

The editor can also drag down the performance a lot in some cases, you could try making a shipping build to the game to see if it differs in performance.

Also, if you want to get a good graphical overview of what function or thread is holding the game up, profiling with Unreal Insights provides a really nice call graph representation.

I was able to cancel the effect of SSW to restore normal frame rate after adding this blueprint. The delay has to be more than 3 seconds to take effect. I don’t know why.
I tried the performance tools introduced by Rectus_SA, but still no clue. Since it works I won’t look deeper, if anyone knows the reason to be able to deal with this problem completely, please let me know.