Question Can I lower my frametimes and make my GPU work harder?

[AWmk1]

I'm using an RTX3070 with an Oculus Quest 2 to play DCS World. With resolution cranked up, and most other settings (textures, shadows, view distance, MSAA) low, GPU frametimes are ok ~11ms, and CPU times are lower. However VRAM usage is shown to be low ~35% (using OpenXR toolkit). If I raise settings to higher quality, VRAM usage goes up towards 50%, but frametimes go up terribly to 17-20+ms, while FPS crashes.

I'm trying to grasp the relationship between GPU frametimes, FPS, and VRAM usage + other GPU operations, and am hoping my RTX3070 is capable of more than I've seen so far.

 

[ZGR]

I find using the in-VR performance monitoring tools lackluster. I recommend Nvidia performance overlay (alt-r) or MSI Afterburner . You will want to be seeing 90%+ GPU usage while running the game below your max VRAM limit.

Make sure you have 120 Hz mode enabled in the Quest desktop app. Turn off V sync in game. If you are still seeing low GPU usage and below 120 fps, than you are most likely CPU limited. What CPU do you have?

 

[AWmk1]

Thanks ZGR - trying this out now. My CPU is a 5800x3d.

 

[AWmk1]

Here are some screenshots showing that Nvidia perf overlay shows much higher GPU utilization than the OpenXR tool. OpenXR has something called turbo mode which helps smooth out spiky frametimes amazingly. In the second image you can see the frametime graph with the yellow/green lines go from smooth to spiky as I switched off "turbo mode". I think it may be contributing to problems - as the devs said it could - so now I'm hoping to figure out a way to smooth out frametimes without it. So far I like what I see.



Turbo mode
Note: This is a highly experimental feature. If it makes your game crash or misbehave, please disable it.
Turbo mode makes the game entirely ignore any frame timing or throttling dictated by the OpenXR runtime. In other words, Turbo mode forces the game to draw and submit frames as fast as possible regardless of any recommendations or policies from the OpenXR runtime.
Turbo mode can increase your frame rate under certain conditions, but there is no rule or guarantee.
Turbo mode can also have undesired side effects:

• Any statistics or performance measuring tool might now present incorrect data. For example, on WMR, when using the performance overlay, all app CPU/GPU values will read 0.
• Any feature of your platform that relies on frame timing data, such as Motion Reprojection/Motion Smoothing/ASW, will not behave correctly. For example, on WMR, the motion reprojection will not engage automatically anymore, but it can be forced via the Lock motion reprojection option.
• Latency is increased, in a way that may or may not visible.

Note: Turbo mode is offered as-is. There will be no support for issues filed while using Turbo mode.

 

[ZGR]

I got the same CPU. The only flight sims I can play at locked 120fps in VR are IL2 and Elite Dangerous; both look really dated now. You probably are near the limit of your CPU for this game. But your framerate isn't bad.

Elite Dangerous in VR will just say 60fps on my main monitor so it does depend on the game to trust the nvidia overlay for FPS. The GPU usage is accurate all the time at least.

I am setting my Quest 2's resolution to 1.9x scaling in the Quest desktop app, and then setting SteamVR's resolution to 100%. This seems to look best for me, and makes my in-VR overlays look really crisp. You could also try setting up DSR in the Nvidia Control Panel and adding a few higher resolution options to choose in game. I am kinda liking 3413x1920 using that method.

I'd probably be content with your performance. I doubt moving up to the 7800X3D will be a game changer. Looking at FS2020 benchmarks for that new CPU next month might be a good idea nonetheless.

 

[AWmk1]

I'm happy with it even at 60Hz when I'm able to use OpenXR in turbo - but it seems like there's a little friction between the game and the app as with a recent game update you now have to add " --force_enable_VR --force_OpenXR" to the shortcut target to get it to run, and it seems to crash a lot now. If I don't have that app open and in turbo mode, I either have VERY spiky frametimes or have to run in reprojection and deal with ghosting- which really sucks in a dogfight. I need to test out turbo mode more (which disables reprojection) to see if it really is better.

Regarding DSR - I see it in the global settings, but it's absent from the game-specific tab. Not supported I assume?
Global:



DCS settings:

 

[ZGR]

For DSR to work, you have to check those boxes and hit apply. But It will only work in modded VR titles, like Cyberpunk VR, GTA V VR, and any game using Vorpx and or Rehade SuperDepth3D (it is free) game you want. SuperDepth3D works pretty well on X4 Foundations, so that 'flight sim' is what I use DSR for. Sorry I didn't word that properly. It won't have a purpose in native VR titles.

For IL2 and Elite, my in-game monitor resolution is a tiny 800x600 window which has no effect on the in-game VR resolution. This makes my GPU usage a lot lower so I can maintain locked 120fps.

I'll try out DCS World to see how it runs; but I am not looking forward to mapping controls!

Edit: Got DCS. Got a big performance boost from checking the VR headset box and setting render resolution to 0.8x. Then enabled VR Mirror option. Set trees, scenery and civilian traffic to lowest. In-game, set your monitor resolution to 1280x768, and restart game without VR. Then restart game in VR. Now the game will be a tiny window on the main monitor to gain fps.

But on my monitor, it says I am at 60fps, just like Elite. using SteamVR's GPU performance monitor to verify I'm getting around 100-110 fps and am bottlenecked by 5800X3D. Not bad!

 

[AWmk1]

It's a very fun game! What HOTAS do you use? And which aircraft?
Which GPU?
Can you grab a screenshot of your frametime graph? I was using the ingame graph which is RCTRL+pause/break hotkey.
My GPU always appears to bottleneck the system.

I had some wonderful performance as well at times, but I was in the f-16 which has the display screens and your rez needs to be high to read the numbers (without using VRzoom which makes me go cross-eyed).

I don't have the steam version of DCS - so I'm not sure how to try the steam GPU perf monitor you mention. I added it as a non-steam game to my library, which seems to work ok, but had trouble using FPSVR as that app says something like "don't use this app with Oculus API - you'll waste performance" when I open it.

I'm still trying to understand if it's a VRAM size or bandwidth or speed issue for me. And I've now packed away my VR since I'm moving house soon... so no more experimenting. I hope to buy a better GPU in a year and come back when the game software is more efficient.

 

[AWmk1]

The biggest issue you might find is that even with stable FPS while flying around, FPS gets crushed during a dogfight / hard maneuvers swinging from high to low / barrel rolling while looking at the ground. The aircraft you are trying to follow across the sky will stutter and it is a very sad experience!

 

[ZGR]

I was testing with a 3080 at 1770 MHz with 0.792 V on the core. Moving to 1890 MHz saw no performance uplift. I'm currently in the market for a HOTAS, so I was playing DCS on a controller with a bunch of paddles, with most controls unmapped, so my flight and taxiing were quite boring.

When you hit max VRAM usage and it starts to overflow into your RAM you can hit extreme performance degradation. GPU usage will plummet and the game will stutter a lot. I wouldn't judge VRAM usage alone though. Quite a bit of titles I play will hit just below max VRAM usage and stay there without any performance degradation. Running multiple games at once is a good way to see this in action.

When I take an in-VR screenshot, the SteamVR GPU performance overlay isn't showing up. Moving up to a 4090 should allow you to do native rendering. But 0.8x with higher resolution cockpit doesn't look too bad.

 

[AWmk1]

Awesome, enjoy! If you need some hotas inspiration, I like the Warthog but it needs a couple upgrades to be great - the stick gimbal can be replaced by a VPC WarBRD, and the slew control can be replaced by one from Delta Sims. I've heard people say just start with a Virpil HOTAS from the get go. Here's my hotas mapping for falcon BMS which mostly translates to DCS for the F-16.