We have conducted some tests.
Note
Normally we use NVidia Frameview to get statistics, but since we need to organize the data, this time we only checked the visual values on the HMD using Oculus-Debug.
Environment
Hardware: ASUS Proart X670E Creator/AMD Ryzen 7950X3D/Gigabyte RTX4090 Xtreme Waterforce/DDR5-5200-JEDEC(CL42)-32x2 /Intel Optane 905p
HMD:Oculus Quest 2/Wired(USB) with OpenXR Toolkit 1.3.0 GA3
DirectX:11(DX12 in VR is buggy in my current environment.)
MSFS:1.31.22.0(SU12 public build)
Graphics options:VR Ult all/Grass cockpit refresh rate=HIGH/TAA Supersample=100
Aircraft:FBW A32NX Experimental build(f560618) (PMDG 737 is not in my possession, so I substituted A32NX.)
Airport: Haneda Airport 34L
Add-ons: All 360GB/480 add-ons I normally use are enabled. Haneda Airport has an addon for object modification.
Add-ons that affect flight: GSXPro/FSLTL/FSRealisticPro/Aiflow/Aiground and Voicemeeter for voice mixer
Altitude: 200-500ft (for high load simulation. Passing between buildings)
Traffic: Realtime online(Airport life(50/1/50) Land and sea traffic(20/10/50))
Weather:few cloud
Time: noon (for VFR test because it is not visible at night)
Oculus settings
Rendering resolution 5408x2736 (maximum configurable)
Oculus refresh rate
Checked at 72/80/90/120, 72FPS is the smoothest due to frame time.
90/120FPS often fails to meet the ASW requirement of 45/60FPS, which is half the FPS, and hitches occur.
Although 72/80FPS may be preferred, in the case of 80FPS, there is a drop and recovery of 2.5 fps in steady state, which is not stable, so 72FPS (default) was chosen for stable measurement.
Therefore, 72FPS is set as the default for stable measurement.
TLOD is tested at 100/200/250/300/400.
TLOD100
During takeoff and runway, 36FPS is possible in all areas including V1/VR. 36FPS is maintained even when flying between buildings at 200-500ft. Rarely drops on loading, but recovers in about 1 second.
TLOD200
It drops to 31.5FPS for about 1 second only at V1/VR, but after that, 36FPS is possible in the whole area. 36FPS is maintained even when flying between buildings at 200-500ft. It rarely drops on loading, but it recovers in about 1 second.
TLOD250
It drops to about 29FPS in V1/VR for about 2 seconds, after that it is almost 36FPS, but it drops to about 29FPS on loading. It depends on the object density.
TLoD300
During V1/VR, it drops to about 24FPS. After that, it is between 27FPS-36FPS. When memory recovery (aka.GC) of objects occurs, it may drop to about 10FPS.
TLOD400
Almost always in the 20FPS range, rarely dropping to single digits.
There is no noticeable difference between the external and internal viewpoints visually, so we omit it.
Conclusion
Under the above conditions, I think it is safe to say that 36 FPS can be maintained even with all VR options enabled, generally up to TLOD200-250.
APP Photon-to-Motion delay is 65-70ms in all regions, 45ms when lightweight, and momentarily exceeds 100ms when a hitch occurs, but it recovers quickly except for TLOD400.
At 72FPS, one frame is 1000/72=13.9ms, which is stable at about 4-5 frames delay.