Bad performance (Low FPS) with World Update 3 and new London photogrammetry - possible memory leaks

I have a high end system and never seen frame rates fall to less than 30FPS (driving a 4k monitor) with graphics on “Ultra”, generally they’re in the 40 to 55 range wherever I fly in the world. The issue started with World Update 3, and is not only in the London area. This morning I was on a 2-1/2 hour flight (Clear Skies) from EGPK to EGLI and FPS started as usual in the 40-55 range. After about 30 minutes the GPU load would drop randomly from 100% to 60-70% and the FPS drop down to the mid 20’s. After a few minutes they would return to normal. As the flight progressed these GPU load drops increased in duration and frequency and the FPS dropped even lower. For the last 30 minutes of the flight the simulator was stable with the GPU load at around 40% and the FPS pegged at 17 -almost unflyable. My system is:

  • Intel Core i9-10900K 10-Core 3.7 GHz CPU
  • Corsair Dominator Platinum RGB 64GB (4x16GB) DDR4 3466
  • ASUS ROG Strix GeForce RTX3090 O24G
  • nVidia GeForce Driver V461.72

After quiting FS2020 and rebooting the PC everything was back to the usual 100% GPU load @ around 45FPS. However after 15 minutes of flight the cycle of random GPU load and FPS drops has started again…


If you are experiencing this issue, please vote to bring it to Asobo’s attention.

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Glad to see that its not an AMD /Intel thing. This is exactly what i was describing in a previous thread happening to me.

My system
Ryzen 5900x
32 GB Gskill Trident Z Neo DDR4 3600
Powercolor Red Devil 6800XT
Radeon Software 21.2.2

I have voted!

I’m amazed nobody has replied to you on this yet.

How did you turn on mesh mode? This seems like it would be a really good tool to hunt down, screenshot and report reversed faces (is there a mode to enable face-fill or similar?) and other nasty stuff like janky lines and generally just triangles where they don’t belong, etc.

Granted, everything looks scary in wireframe mode, but looking at just this screenshot you posted, I can see buildings which should absolutely have FLAT roofs, consisting of maybe 2 triangles, that look like they have a weird central point of elevation on them and thus many more triangles than probably makes sense…am I seeing things or do you see that too?

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I don’t know why, but I’m glad you’re asking!

You just need to enable Developer mode and navigate in the View menu. I’ll update this post later with the exact label if you don’t find it.

I can see indeed poorly optimized polygons leading to displaying more than necessary in general, more than necessary even more in the distance, and other errors related to flatness indeed.

What I really don’t get at all with FS2020 3D modeling and optimizations, is that Microsoft has purchased a company specialized in this tech and they are not using it for FS2020.

The company is Simplygon and I’ve already mentioned it in a few posts:

LOD problems - Trees Fix Revisited - #92 by CptLucky8

Landmarks shifting up and down + Half of them not loading correctly (still not fixed in - #42 by CptLucky8

With Simplygon they could in theory among other things:

  • Reduce LOD model complexity while PRESERVING the overall shape (aka anti melted buildings)
  • Generate impostors in the distance preserving details and transparency.
  • Automatically bake AO in the cockpit and save pixel shader resources for the rest.
  • And much more.

I’ve no doubt Asobo’s engine is already doing some of these things, but there are definitely cases we can see in the game where the mesh and polygons could benefit more from this technology (on paper at least, maybe it is not this much effective in practice).

PS: don’t miss PG mesh holes as well:
[World Update 3] London Photogrammetry Mesh Holes

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This appears to me to be the same issue as the thread below:

They should be linked together and the Votes combined.

Haven’t had this problem since the launch until the world update 3. For the past 2 flights over 1:30 hour, this annoying problem hit back.

I also experience random drops in framerate, where the frames suddenly drops from 30 fps (v-sync on) in 4k to 15 fps for 10 seconds up to one minute before it recovers back to 30 fps again. During this period the “manipulator” in developer mode is heavily impacted, and the graphics card almost idles at 30 to 50 percent performance.
I suspect it relates to a data / cpu issue, however I haven’t had this problem until world update 3. The drop in frames seems to happen at random, however maybe when flying close to ground, near an airport, and also flying over area with no photogrametry.
I have tried updating bios and reinstalling the entire computer, however the problem is still there.
My specs are:
Ryzen 9 3900X
Asus TUF RTX 3090 OC
Corsair 4x 16GB 3200 MHz ram
1TB Seagate FireCuda 520, PCIe gen 4
ASUS ROG Crosshair VIII Hero
Corsair RM 1000W power supply

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Hey, I experience similar issues with the A32NX, and am not sure if it is the airplane or the sim yet. Can you try seeing if you get the same fps drop and rebound at the same location again? Also, do you have custom scenery installed in the areas where the drop occurs?

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Yes i also found Out that custom scenery ist causing more chances of slowdowns. For example Drzewieckis Chicago Landmarks. I still think its a vram leak.

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Hi, I am currently checking the drop out using dev mode. The fps drops from 50 to 18 consistently, not any lower not higher. Then comes back up in a minute or so. During this time, the “manipulator” frametime and the mainthread frametime is excessively high (>50ms) from around 10ms during normal ops. This happens on the A32NX custom FBW mode.

It seem to me random and no, I havn’t sceneries installed.

I am also getting dreadful performance when flying low through London only. Not getting this with new york or any of my other dense 3rd party addons. I have to believe this is the result of 2 things. 1) High density in London. Many many buildings and structures. 2) Poor optimization. I don’t think Osobo has enough time to optimize the scenery as the 3rd party creators do. I would love to have this optomized. I love the city, but the drastic drop in fps ruins it for me.

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Something is definitely wrong with this update I ran my game on ultra before and had steady fps 35-40 now I’m getting low 20s

I’ve changed all settings and the only thing that makes a difference is the Terrain Level Of Detail something is definitely bugged with it. My sliders were both set to 100 before the last update. When I drop the slider for terrain level of detail the fps go back to what I was getting before

But when flying the terrain looks terrible my fps was perfect before the latest update I don’t get it

I dropped the UK Photogrammetry and left the blgs. and points of interest alone. I can now fly low at 35-40 fps, and never having been to London I am not the wiser. Happy now.

I’m getting good fps throughout the UK update with the exception of London itself.

Not sure if it’s worth mentioning but I have seen some odd juddering using reprojection (OXR) in scenery where it’s otherwise been completely smooth during the flight - no apparent loading or heavy scenery involved - just appears out of the blue.

I put this down to the use of ‘Automatic’ setting on OXR as I had it on by mistake and I usually fly with ‘Always on’ which has never caused me a problem and it seems to be more efficent.

@sneaky74 Yes this might be the case indeed because sometime it switches between two modes depending on the actual fps and a threshold when in Auto. This is happening with the Index and SteamVR too since WU3. The only explanation I have for now is the FS2020 rendering code is stalling when updating some DX11 buffers and it looks to me these are vertex buffers mostly (per cross checking some settings which are mostly vertex buffer related and the actual glitches at runtime).

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Yep that was my thought also (but without the deep technical knowledge haha). :joy:

Pity as ‘Automatic’ is nice as you get a crisp menu UI as reprojection is clearly not needed there and it can adapt when you’re in heavy scenery - the benefit being you get a clearer image depending on how little the reprojection is being used (x2 or x3 - runtime preview enabled).

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So what puzzles me with London is there are clearly graphical glitches in the scenery - the Thames has these strange reflective spot which appears to be windows to scenery rendered below the London photogrammetry.

It wouldn’t suprise me if it wasn’t just trees they were rendering twice but a completely new layer which should be culled from view.