Valve Index frame rate locked at 40 when at 120hz

[KungFu]

Just got my index last week and was previously using a Rift S. Since I can, I use 120hz for iRacing. However it looks like the refresh rate in SteamVR cannot be set per application and is global.

 

I started DCS and noticed that my framerate would never go above 40fps, even with the graphics set at absolute minimum. With my rig this made no sense. On a whim, I lowered it back to 90Hz in steamvr and viola, framerate 45fps steady.

 

So is anyone else seeing the same? It's probably not the best to run at 120Hz with all the reprojection anyway but I think it is something DCS peeps should be aware of.

[Strong05]

Running 120 here and frames go between 40 and 60 and will drop below that for busy parts of the map. Seems to be able to interpolate between multiples of 20 for the most part. What PD are you running? I've found this has a big impact on FPS.

[KungFu]

I'm running a PD of 1.0 in DCS and 100% in SteamVR...so I'm not using any SS at all at this time.

 

I've even used the lowest settings in DCS and can't get over 40fps unless I use 90Hz..(although I haven't tried 144Hz yet.

 

Really odd behavior. I removed everything steamVR related and reinstalled when I switched from the Rift S to make sure all was clean. But just changing refresh rate shouldn't have this behavior.

[Strong05]

What game settings do you have? MSAA also kills FPS along with default shadows for terrain. Try the VR preset button as well (that magically fixed my FPS problems, even after setting everything back to where I had it I picked up 10fps or more).

[KungFu]

I've used settings even lower than the ones set by the VR button and it never gets above 40 when using 120Hz refresh.

[RealDCSpilot]

120 Hz means that your system must be able to render a single frame twice in 8,33 ms in an appropriate resolution for VR. I don't know any hardware that is able to do that for DCS. Even 11,1 ms is usually impossible to reach (90Hz), maybe only if every option is set down to extreme lowres and most ugly possible. The 120 Hz option is not something that will activate a super boost mode, it will only work if the game and your system are able to run it. What you are experiencing is the 2nd fallback stage of motion smoothing because of insufficient frame time, 1st stage is half the frame rate 60 HZ, 2nd stage is one third of the frame rate -> 40Hz. For your system, i would recommend setting 90 Hz and force "motion smoothing on" to deliberately lock the framerate at 45 Hz (frame time of 22,22 ms). Or you can go even lower with 80 Hz mode and forced motion smoothing which gives your GPU and CPU 25 ms to render each frame per eye.

Edited August 2, 2019 by Alec Delorean

[kmw072671]

+1

 

I just got the Valve Index and was using the Rift S, frame rates with the Rift S were 50-90 depending on the mission. With the Valve at all the same setting conditions I'm locked at 30 FPS, not sure whats going on.

 

I dropped the Index down to 90Hz but did not see an impact, this is not good enough for VR. Not sure why the Rift S was much better at FPS with all settings the same.

 

I have a decent computer, 32GB, 2080 TI, I7-9700 and the frame rates suck...

 

Is this a DCS issue with the Index?

[OG84]

hhm i mean index has much higher resolution, so 1million pixels more for your gpu.

 

I have a vive pro (same resolution as index), and get 45+ fps with my 2080ti. So 30fps with lowest settings sounds a bit low for your 2080ti). for 1080ti it sounds reasonable.

 

try turning motion smoothing off.

Edited August 7, 2019 by OG84

[Supmua]

Valve Index frame rate locked at 40 when at 120hz

 

Please see my mini guide on settings in the hands on thread. The device only sucks if you do not set it up properly.