PSA: Performance problems with latest update might be rooted in Trees (calling for feedback)

Hi,

I have noticed, most likely like many of you, there are performance problems since WU3. The hotfix is certainly “fixing” another type of bug also causing stuttering and/or freezes, but there remains occurrences of unexplained sudden loss of fps/perf. This might be even more noticeable in VR.

So far, I’ve attributed most of the stuttering to the game updating the vertex buffers (mostly). I could find some correlation between what the rendering engine is supposed to change on screen, and how this is usually done in a modern rendering engine. I might be wrong of course because I have no access to the source code nor I can use NVidia NSight or similar developer tools, but the correlation seemed strong to me. In short: when the game needs to upload massive new vertices to the video card, it does so in a way which sometimes is oversubscribing the available VRAM, and this is causing a CPU/GPU sync/halt problem.

In effect, keeping TLOD 100 and Buildings + Trees Medium is helping a lot reducing the occurrences. To me, Trees are supposed to be less taxing to some extent, because there are few varieties and lots of instancing, whereas buildings are supposed to be more taxing, because there are much more variety and this reduces some of the instancing advantage compared to trees.

Having said this, I’ve been trying a few things lately to confront the game to its performance. In particular, I’ve been interested in evaluating the impact of Trees overall, and to make sure I would saturate the “buildings” side, I’ve been trying this over photogrammetry areas. In these areas, the buildings and every ground detail is actually a giant mesh (there is no longer individual synthetic buildings), but the PG trees are overlaid with synthetic trees.

And here is the most interesting finding to me: when setting Trees to LOW and flying close to the ground, you can see Trees changing nearly every frame around you even just below you. In other words, the rendering engine and/or game is simply doing its job of changing Trees details based on distance (LOD), but it is doing so in so short distance rings around you that Trees are changing always. However when setting Trees to ULTRA, it is effectively rendering trees as you’d expect with regard to LOD/distance.

So back to the topic of performance problems, I’ve been trying Trees ULTRA everywhere, keeping Buildings to MEDIUM and Terrain LOD to 100, and in doing so, I’ve noticed much less stuttering and freezing than before.

In short, the main point I’m wondering is if you’re also observing the following:

  • Whether with Trees LOW you also observe them changing shape all around and close to you.

  • Whether setting Trees to ULTRA + Buildings to MEDIUM + Terrain LOD 100 is making any difference for you in terms of performance / stuttering / freezes

I’m posting this so that you can try out and compare on your systems, and report in this topic, with the following in mind:

  • I believe there is a bug with the game and rendering engine and the way it is handling Trees which is causing a lot of the perf problems in itself.

  • Some of you are using Object LOD 200 and/or Terrain LOD 200 and/or Buildings ULTRA etc… And these will make it harder to isolate a possible culprit of course, especially if the core issue is rooted in the game engine and the way it is updating DX11 buffers.

  • Nevertheless, the point is to compare Trees ULTRA with Terrain LOD 100 vs Trees Whatever with Terrain LOD 100 first and foremost, while making sure Buildings are less prone to impacting the performance in keeping it at MEDIUM, and

  • To see whether regardless of your hardware, changing the Trees is mostly better or not, regarding stutters / perf / freezing issues.

I hope this will help Asobo gathering some useful feedback to resolving this problem. In any case, whether this is changing or not your experience, it will remain valuable feedback either way.

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I’m away from sim rig working on a project until end of week but I’m definitely going to test this at the weekend.
Will update if I see anything that confirms.

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I have noted that setting Terrain LOD to 100 has helped reduce the “main thread” problems at certain areas after the latest Asobo fix ,I really wish I could roll the game back to the state it was before the devastating UK update.

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I don’t have great frame rates (passable most of the time in the western US) but generally my settings are…
Terrain LOD = 200
Terran Vector Data = High
Buildings = Medium
Trees = Low
Grass = Off
Object LOD = 200
And yes LOD is making any difference for you in terms of performance and quality

@meh1951 @Ixoye56 Thank you for your quick feedback!

Please note the main topic is not confirming whether adjusting Terrain LOD is helping in itself, because for sure it does. I might have failed to express the main point so I’ll try differently:

[edit: consolidated information in the OP]

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Well thought out, tested, and presented. I’ll work on your theory tonight. Thanks.

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Here is my results…don’t think that Trees made a big difference
My System
Device name zzzzzzzzzz
Processor Intel(R) Core™ i7-9700K CPU @ 3.60GHz 3.60 GHz
Installed RAM 32.0 GB
Device ID zz
Product ID 00330-80024-05178-AA937
System type 64-bit operating system, x64-based processor
Pen and touch No pen or touch input is available for this display

OS
Edition Windows 10 Pro
Version 20H2
Installed on ‎10/‎14/‎2020
OS build 19042.867
Experience Windows Feature Experience Pack 120.2212.551.0

Scale and Layout
100%
2560x1440
Landscape

GeForce RTX 2010 Super
Driver Version 465.89

Monitor HP 2560x1440, 59Hz


Current FS Setup
Terrain LOD = 200
Terran Vector Data = Ultra
Buildings = Medium
Trees = Low
Grass = Off
Object LOD = 200
Volumetric Clouds = Ultra
Texture Resolution = Ultra
Currently flying Phoenix and Arizona, Nevada and California I get…
34-44fps


change Trees to Ultra
Fly around Phoenix at 2500 feet for approx 15min

Terrain LOD = 100
Terran Vector Data = Ultra
Buildings = Medium
Trees = Ultra
Grass = Off
Object LOD = 100
Volumetric Clouds = Ultra
Texture Resolution = Ultra
Currently flying Phoenix and Arizona, Nevada and California I get…
35-38fps


change Trees to High
fly around Phoenix at 2500 feet for approx 15min

Terrain LOD = 100
Terran Vector Data = High
Buildings = Medium
Trees = High
Grass = Off
Object LOD = 100
Volumetric Clouds = Ultra
Texture Resolution = Ultra
Currently flying Phoenix and Arizona, Nevada and California I get…
37-39fps


change Trees to Medium
fly around Phoenix at 2500 feet for approx 15min

Terrain LOD = 100
Terran Vector Data = Ultra
Buildings = Medium
Trees = Medium
Grass = Off
Object LOD = 100
Volumetric Clouds = Ultra
Texture Resolution = Ultra
Currently flying Phoenix and Arizona, Nevada and California I get…
35-39fps


change Trees to Low
fly around Phoenix at 2500 feet for approx 15min

Terrain LOD = 100
Terran Vector Data = Ultra
Buildings = Medium
Trees = Low
Grass = Off
Object LOD = 100
Volumetric Clouds = Ultra
Texture Resolution = Ultra
Currently flying Phoenix and Arizona, Nevada and California I get…
37-44fps

@meh1951 thank you for taking the time for this!

It doesn’t change much fps but does it make any difference on your system with regard to stuttering/freezing and such?

PS: you might want to edit your post and change the typo in your GPU model!

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Nothing noticeable.
I’ve changed the Trees parameter to make them look more realistic.
The LOD seems to push their draw distance further out. At 100 it’s drawing trees right in front of me.

So, yes. The game engine is changing trees constantly when set to low (even those really close ones). I have definitely more micro-stutters with trees set to ultra than when set to low (VR, i7-7700k, 1080Ti, 64 GB RAM).

Terrain LOD is my big frame rate killer. There seems to be minimimal impact with other settings. But if I put Terrain LOD over 100, my frame rates tank hardcore. I typically keep most of my settings at High and Medium with a couple of Ultra. Most of those settings may affect my frame rate by 1-2 fps increasing or decreasing. Overalll pretty minor though compared to TLOD.

I currently keep my TLOD at 85 as a “sweet spot” that keeps me in a playable frame rate range of high 20s / low 30s. At 100, I can’t break 25 fps. If I go any higher, I drop below 20 and eventually go into single digits, making it unplayable.

Object LOD, by contrast, seems to make no appreciable different in performance, so I keep it at 200.

Prior to WU3, I had both my LOD settings to 200 and saw very little noticeable performance impact from adjusting them either up or down. Since WU3, I’ve had to lower TLOD because it was a giant fps black hole.

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Thank you for sharing you feedback about the various TLOD settings and their impact on the overall fps on your system. There is definitely some good info there.

Have you actually tried comparing Trees ULTRA vs Trees LOW with same TLOD 100 on your system so that you can further contribute to this specific topic too?

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I probably did at some point, because I’ve tried pretty much every settings to try to determine what was causing my poor performance after WU3. The only thing I could reliably point to making any appreciable performance difference was TLOD. Other settings seem to have minimal impact at best. Like I said, 1-2 fps at most between low and ultra. Only visual quality is noticeable. Including trees and their draw distance, as you described in your OP.

Prior to WU3, I was able to run everything Ultra with both LOD settings at 200 and get 40-45 fps most of the time. After WU3, TLOD at 200 dropped me into the low teens. I had to dial it back to where I have it now (85) to be able to maintain a frame rate in the high 20s / low 30s.

Also, I find lowering it below 80 has little appreciable performance difference. 0-85 seems to have no difference except on the visuals. Above 85 and frames start disappearing with every tick it’s increased.

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when I set Terrain LOD to 200, I got a lot off stutter and panning the camera was not smooth.

I stick with Terrain LOD 100

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Just flown around the same area changing the trees from Ultra to Low and back again a couple of times - utterly dull 12 minute video recorded and uploaded to Youtube. Resolution isn’t great as was done with the XBox Game Bar quickly , but may help with your theory.

Happy to test somewhere specific under more set conditions if it helps :+1:

R9 3900x RTX 2060S 32GB Ram

Microsoft Flight Simulator 07 April 2021 Trees Low/Ultra Buildings Medium TLOD 100 - YouTube

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@LincolnSixE
Thank you for taking the time to make this video!

It is hard to see in the video and you never know in what proportion taking the video in itself is causing additional problems, so I might just be wrong interpreting what I see in the video, but I can notice:

  • With Trees LOW on your system they are also changing shape nearly every frame as you’re flying, like I’ve seen in my tests (in VR for me).

  • With Trees LOW you might have some stuttering I don’t see with Trees ULTRA:
    .
    Low (some stuttering): https://youtu.be/KMZSEhYpU6w?t=181
    Ultra (less or no stuttering): https://youtu.be/KMZSEhYpU6w?t=519

  • Regardless Trees LOW or ULTRA, this doesn’t seem to be affecting your fps overall either.

This last point is important, because the idea of a LOW to ULTRA setting is to balance the perf for a system. Either your system is so much capable it won’t make any difference at ULTRA, or, the game has a bug causing this setting to not be as effective at reducing the load in LOW vs ULTRA.

There is actually another setting like this, “Terrain Vector Data”, which I find is doing nothing at all (no difference in perf or visuals).

Try taking off from KPDK and switch to an external view - then focus on the tree rendering below. Can you give it a try?

Should back up your test case.

No improvements on my side when switching between Low and Ultra, however it’s important to note that I have a high end machine and my main issue within VR is the shuddering when looking around the cockpit and not the overall performance.

No improvements here

hm. I’m seeing that there’s a huge framedrop when changing the trees initially (~ -20), then after about 20 seconds, the trees flicker and everything stabilizes. With the Bijan Tree Mod, I’m not seeing any difference between Ultra and Medium. I’ll test cities too, this was done at KGCN. There is about a 10 FPS difference between Medium and Ultra with no noticeable degredation in visual quality. As for stutters, not seeing stutters in either.

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