Right eye mirage with volumetric fog and material cloud fogging.

Question: What could be causing this right eye issue, and where/how can i fix it?

While working on the volumetric foreground clouds in our VR scene noticed that our horizon cloud billboards weren’t being obscured by the clouds fogging correctly. (Bottom of 1st image)

When i corrected this by setting the billboard materials Translucency > Apply Cloud Fogging to true, the blending was fixed, however i encountered yet another “VR right eye only” engine defect (Top of 1st Image, Right Eye).

This is only partially visible in the screenshot thanks to the cone, however is immediately noticeable on every overlapping cloud in VR. In VR it almost looks like a weird screen space mirage effect. The issue occurs regardless of OpenXR runtime for both SteamVR & WMR Headsets.

Animated GIF of view through HMD

Right-Eye

To keep this post shorter, this other Right-Eye-Defect thread contains a list of the screen space & post processing features of the engine I’ve turned off and left off while trying to get VR to work in UE 5.3.

While debugging I’ve determined that this issue only exists when using Single Pass Stereoscopic rendering. It and some other ‘Right eye only’ bugs in VR appear to not exist when instanced stereo is turned off.

Most paradoxically, in shipping builds of our testing scene, instanced stereo actually performs worse with a 5.3-6.6ms frame time as opposed to 5.2-5.8ms when it is turned off so something’s broken here.