5K+ Extreme Momentary Stuttering at High Resolutions even when FPS is actually just fine

As I’m learning more about things I’ve run into an issue which I don’t know how to resolve (or if there is a way to resolve it). When I push high-resolutions through my 5K+, for example using the PiTool Rendering Quality at above 1 in a native VR title (Skyrim VR), or when using Vorpx and pushing high game resolutions (FO4 at 4K), I’ll get momentary glitching and hiccups and some extremely strange behavior even when my FPS is absolutely fine. Looking at fpsVR I can see some extreme spikes combined with very low GPU / CPU usage. Once things “steady up” I can usually play just fine (depends on the situation). Looking at that same situation in Vorpx I see that the game might be rendering just fine, but that the HMD FPS has dropped to something like 2 (Vorpx lets you see what FPS the game is rendering at, and what FPS is being sent to the HMD). There appears to be little or no relationship between resources used whether or not this happens, at least in terms of game FPS. For example, using Brainwarp I can set the PiTool quality to 2 and still easily render Skyrim VR at 45fps with no trouble. But doing so will result in aforementioned glitches. FO3 I can run at 4k with zero problems, but FO4, even with Z-buffer 3D (and thus quite high FPS with low 3D overhead) it will glitch. So it’s native VR titles, as well as non-native titles through Vorpx, with slight, if any, relationship between how much CPU/GPU I’m actually using, but a clear relationship when it comes to resolution settings.

Any tips? Thanks!

My rig: Win 10, 4.4ghz Quad Core i7 (liquid cooled), RTX 2080 Super, 16GB Ram.

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Hi some users find after making settings changes. Exit Pitool (pi services will keep running). Pitool seems to sometimes cause spikes in cpu usage.

Another user uses taskmanager & a program prio process viewer to assign pitool & other vr processes to later core/threads (@douglaster)

Sounds like somekind of a memory related hick up.

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Smart smoothing has, at most, a very low tolerance for any red spikes shown in FPSVR CPU or GPU latency graph. Sometimes, these spikes may be low or short enough not to show up in the graph at all, though usually it will be at least 2/3 full.

This is pretty much diagnostic.

Once things “steady up” I can usually play just fine (depends on the situation).

Especially, this has happened to me with DCS World, on both CPU and GPU side.

Based on your PC specs, and ‘very low GPU / CPU usage’, first thing I would suspect is a program running in the background. Some GPU vendors overclocking software (EVGA Precision X1 older versions) has been known to cause problems. Any ‘on screen display’ apps can also cause problems, even though they do not work in VR. Malware is of course always a possibility, but so is the MSW OS itself, and any built-in anti-malware tool. Consider temporarily disabling the real-time anti-malware service.

However, some of the resolutions you cite seem rather high. I am running a heavily overclocked 2080 RTX myself, and IIRC, VorpX at 4k was pretty much a no-go. If possible, you may want to compare with this spreadsheet (which is still a work in progress).

https://github.com/mirage335/extendedInterface/blob/master/param.ods

CPU consumption/affinity is another possible issue. You state ‘Quad-Core’, but does that mean, 8 logical threads, or just 4 logical threads? Experimentally, by disabling cores/hyper-threading, I have found that less than 4 logical threads is definitely too few, due to the several different processes which completely buffer and redirect entire frames (ie. SteamVR compositor).

EDIT: Only 16GB RAM is indeed another possible issue.

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I am, admittedly, using pretty high resolutions (and I also rarely use brainwarp - I’ve found that most methods of fake-frame production make me feel queasy - even the soap-opera effect on modern TVs will sometimes make me feel ever so slightly ill). I’m extremely susceptible to a blurriness “continually try to focus” issue, where if a game isn’t sharp enough my eyes will continually work to bring it into focus and there is just no stopping it. I am not, however, particularly susceptible to low-frame rates in anything except true full-motion VR titles like Skyrim VR (and even in that title I usually leave brainwarp off and just try to keep the fps above 60 or so). Most of what I’m playing are either seated racing-sims (where I’m perfectly comfortable all the way down to around 40fps with no brainwarp) or Vorpx in Lounge mode (where I’m fine as low as 45fps in most titles, again without any form of asyc rendering).

I’ll go in and take a closer look at other resources, but I don’t think the issue is resource-loading. It’s all SSD storage, and with most of the games I run I’m no where near 16GB of RAM in use. I also don’t have any issues like this when running traditional stereoscopic mode to my 3D display using TriDef, and that’s also massively resource-intensive. Anyway it doesn’t “feel” or even “look” like resource loading glitches - the areas all load right up very quickly, all the textures etc. load just fine, and then this problem occurs - it’s very strange and hard to describe. It’s almost as if I’m getting momentary glimpses of different scenes in each eye, it’s just hard to describe I’m afraid. The first time I saw it I thought video-artifacts from overheating GPU, but it isn’t that (GPU running quite cool - case cooling works well and even with a mild over-clock I can push the GPU to 97%+ for essentially any length of time and the GPU never gets above 65 degrees c at 50% fan speed. I’m very surprised and pleased by that). Likewise the CPU never gets close to maximum allowable temps no matter how hard I push it. It’s a 4GHZ 6700k overclocked to 4.4 - so 4 physical cores, 8 logical cores.

I’ll try to get time tonight or tomorrow to test a few different games and see if it is possible specific to Bethesda’s current game engines, as now that I think about it more I’m not sure if I’ve seen it in other titles besides Skyrim VR and FO4+Vorpx.

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I haven’t run into this as yet. But high demanding games may now be running into memory related issues.

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I was more referring to vmemory

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With Skyrim @Fresco has alot of good experience. Running it even on a 980ti with mods.

Brainwarp does not substantially alter the rate of motion in a scene.

Brainwarp, fortunately, does not work at all like the ‘soap-opera effect’ used by TVs. Brainwarp interpolates at most one frame, whereas TVs will smooth everything between far more frames to a constant rate. A lot of people do not particularly enjoy the latter behavior.

IIRC, GPUs at least used to cache their VRAM in RAM. This may not be the case now, but some form of hidden RAM usage is possible.

In a few situations, mostly DCS World, I have exhausted both 16GB RAM and 11GB VRAM.

VRAM exhaustion has, for me, usually caused frame rates to drop near zero.

CPU configuration you specify should be more than adequate for most applications. Congrats on your setup.

TriDef stereoscopic rendering on a 2D monitor is not nearly as intensive as VorpX rendering into a VR headset. In my experience, the latter has been much less efficient.

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Try increasing prerendered frames in Nvidia control panel. I changed that to 2, and also enabled fast sync (whether fast sync makes it through or not is another matter. Probably not?) My reasoning was that the judder is something to do with frame pacing and/or vertical sync and I’d try to give the headset as much time/frames as possible to get the frame it needs to not stall and judder. This fixed up nearly all stuttering/ghosting/judder for me in Pistol Whip. Though I haven’t tried removing it since to completely confirm it.

Hopefully new Pitool should be out in a couple of days and resolve a lot of these problems.

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Fitzy is correct about prerendered frames at 2 as far as I have been able to determine. Testing this at high resolutions did seem to show some improvement.

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Also check your Windows & Gpu power profiles.

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This. Known bug.

Definitely check all power profiles are set to ‘maximum performance’, no power savings at all, including using the ‘maximum performance’ power profile in MSW, regardless of what has been set in the relevant sub-menus.

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OK, thanks! Some good suggestions here that I’ll look into. I tried doing a little bit more testing yesterday, but hit a wall of other problems that basically prevented that. I have only 3 actual VR titles, AC, PCars2 and Skyrim VR. Both AC and PCars2 do not respond to the Pimax Quality slider for me, leaving me with only a single native VR title to test. I’ll have to see if they respond to the Steam VR quality settings or if I’m hitting that Steam VR maximum rendering resolution wall I’ve read about that requires a Steam VR .ini file tweak I think(?). I’m also wondering now if what’s really happening is that two (or more) different pieces of software are attempting simultaneously to control the rendering resolution, or some other basic setting that just isn’t working the way I think it should. I’ve had to override all my Steam VR auto-quality settings, for example, and am running titles at 100% quality (otherwise Steam keeps throwing away resolution in the attempt to give me 90fps, which I neither need or want in most of what I’m playing).

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Also when looking at hicups focus on the frame time numbers rather than the frame rate.

My tests show, if anything, it is the SteamVR applicaiton resolution setting that won’t scale too high, not the total number of pixels. Setting PiTool Render Quality all the way to ‘2’ should be fine.

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Oh No! Another wall of text!

TLDR: It appears that trying to push extremely high resolutions will cause this problem to appear at higher frame-rates and lower frame-times than it otherwise would.

I spent a couple straight hours this evening just trying various settings. I also benchmarked the system repeatedly with Unigine Heaven in a window so I could watch GPU-Z and CPU-Z and monitor processes etc. As far as I can tell I don’t have any weird background processes or anything like that causing issues. So I think I can safely eliminate that.

Using PCars2 (which does respond to PiTools Quality settings it turns out, but there isn’t any actual visual quality improvement, the performance just diminishes) and Skyrim VR and fpsVR, I’ve found that I can push FPS and Frametimes clear down into continuous red without seeing these issues as long as I’m doing that with features that aren’t related to the resolution I’m trying to drive. So, looking at PCars2, I can just crank up the in-game eye-candy up until I’m way way down at like 30fps and the GPU Frametime graph is just a solid unending bar of red, and it does not display the problem I’m talking about. But if I turn off the eye-candy and then drive the performance down to right around that same 30fps by increasing the resolution, then I’ll get the problem. In fact, even if turn all the eye-candy down and push the resolution up and the fps and frametimes are shown in fpsVR are better (and in the yellow instead of in the red), I’ll see this glitching. Likewise, running FO4 through Vorpx (very poor performance overall - Vorpx does some great stuff, but even in lounge mode is no where near as efficient as TriDef was as converting games to stereoscopy unfortunately) I see the same issue. Running at 2560x1440 in G3D I see none of these glitches even though the fps and frametimes are unusably bad (like clear down at 15fps!). However, try to push 3840x2160 in Z3D and even though the FPS and frametimes are much better and playable (40+ most of the time) bam I start to see the glitches. (No, the problem is not related specifically to Z3D.) I can eventually start to see some random and momentary glitches at lower resolutions, but only if I push game settings to the point where performance is close to nil. I’ve also found that either the Steam VR quality setting or the PiTools Quality setting will cause the glitching, so it’s not specific to the PiTools control.

I think in the end this is probably down to GPU performance overall, but that there is some other factor at work, as increasing the resolution makes this problem occur at much higher framerates and much lower frametimes than it does at lower resolutions. In other words, a problem which I might start to see clear down at something like 10fps when driving a title at a lower resolution, will show up at 30+fps when trying to drive a title at a higher resolution. But it isn’t strictly resolution-based, as I can drive some older/less demanding titles clear up at 4K resolutions without issue.

There is a memory setting in steamvr vr that use to be capped at 4g. I believe they raised that to 8g a while ago. This setting sets the upper bounds for the resolutions available. Assuming you have the ram you could probably bump that up a bit more to allow higher supersampling rates.

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It has nothing to do with RAM. It’s a resolution limit and was 4096 pixels (vertically/horizontally per eye), but should be set to 8192 pixels by PiTool:

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Visual quality usually does not improve noticeably with current headsets past a total super-resolution of 2. As headset resolutions improve, getting closer to the resolution of content and human vision, this total may be reduced further. This is the kind of thing my spreadsheet is used to calculate.

You are correct to infer overall performance is the problem at this point, but not specifically GPU. Sharp glitches in otherwise decent framerates usually happens when some CPU task does not have sufficient time to complete.

Your CPU is fairly new, and Intel. Upgrading it further unlikely to solve your problems, though that did work for my use case, so it is possible.

RAM bandwidth theoretically could cause this, but this is not likely, and there is not likely to be room for meaningful improvement. I have not managed to produce any data showing RAM bandwidth affecting VR performance.

If you are sure no background processes are interfering, I would suggest lowering the resolution somewhat. Of course, keep in mind a 2x reduction in vertical resolution, results in a 4x reduction in CPU processing. Very small changes may make much more of a difference in performance than visual quality.