I might be wrong but I believe the newest threaded mesh optimizer Sebastian was mentioning in a Q&A might have been introduced around 1.12.13. I’m thinking of this one because I’ve reported early on the first time I’ve posted “My VR Settings - Index” how I needed to lower TLOD to 50% otherwise it would be stuttering in VR over PG areas, and I attributed this (when cross checking other factors) to the vertex buffers update taking too much resources/time and stalling the rendering loop.
WU3 is definitely worse and is stalling much more often in VR particularly. I believe it is the same bug amplified this time. It is remarkably visible over London PG and when looking at the unnecessary mesh complexity, it further reinforces to me the vertex buffers handling*
Today someone has posted a video in the VR forums which perfectly illustrates the problem to me:
Frame drops only on certain spots, and only in VR (ex: LFPE 25R)
I might be perfectly and certainly wrong about this but I believe:
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FS2020 rendering engine is having a bug introduced since the VR official release at least, with the DX11 buffers update code,
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Or it is using the DX11 API in a way which causes CPU/GPU sync stalls (like waiting on a wrong fence or something similar).
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It is possible this bug is related to changes in the rendering code logic, being recoded for the upcoming DX12 and for example wrongly merged in the DX11 code base, or rightfully merged but without checking the consequences for the DX11 implementation,
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Or it just didn’t trigger a regression bug in the automatic DX11 tests because these tests are coded in a way which doesn’t exhibit the problem,
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Or add your own speculation here…
In any case, all external and visible indicators are telling me the engine is stalling when updating buffers. It might just be a side effect of something else though.
*Problems with the London PG mesh illustrated:
[World Update 3] London Photogrammetry Mesh Holes
Update:
Filed in Zendesk as:
Request #95862 Rendering engine bug updating DX11 buffers
Here are some recent comments I’ve posted related to the same issue, which will give some more feedback and context:
VR in MSFS is starting to lose its luster for me - #96 by CptLucky8
Solution for Stutters & Pauses (updated for SU5) - #446 by CptLucky8
Rtx 3080 vs 3090 - #27 by CptLucky8
I believe it is paramount FS2020 also implements a user facing debugging log: