nVidia's "Single Pass Stereo" VR Performance in iRacing

Here’s an interesting investigation of iRacing VR performance on nVidia cards:

TL;DR: “…there is a near-zero difference between SPS On or Off.”


Well, that puts the final nail in the coffin for that particular VRWorks feature then, considering the dissertation the author of this article references, had already not only suggested as much, but also pointed out the multiple manners in which it, due to its presuming symmetrical frusta, tends to lead to incorrect rendering (especially for the right eye). .

I don’t believe every title that renders e.g. ambient occlusion wildly differently between the eyes, are using SPS – developers are probably quite able to mistakenly reuse a single frustum for the view-dependent fragment shader runs for both eyes, without NVidias help, but it’s a start – could maybe bring some much needed attention to the matter. :7


All i do is irace in vr. the 10-15 percent performance you get with SPS can be the difference to getting solid or mostly 90 and the fps fluctuating all over the place.

Also, given architectural differences between sps on the 20 series and 10 series cards … there are additional settings only available in INI files to change hoe the eyes are rendered. There are 3 profiles, 1080 users are suppose to figure out which one fixes the image for them.

But, as he noted iracing is a mostly singlethreaded game, so SPS isnt goimng to get you to constant 90… because your CPU is you bottleneck. If you can get smooth 90… SPS will allow you to turn on a couple more graphical features.

There are multiple spreadsheet out there where people have gone through the settings one by one to show the performance impact per settings.

Also it looks like he might have ovr toolkit running which also taints the numbers.

The only data he posted from the runs that matter are the Frametime numbers(specifically the worst frame times) . So, when i configure iracing I try to grab a demo from the most cpu heavy recording i have… then try to find the graphics settings to ensure i dont drop any frames. In my cause the headset is set to 110 hz.

Then I leave those settings in play until the next update.

If you’ve never optimized your system to get max fps always. You’ll never see the real benefit of the extra 10%.


Absolute FPS isn’t always a great measure of performance in VR. SPS helps considerably with frame time consistency. Always surprises me when I see reviews that use absolute FPS as the one and only measure of quality and comfort.

A lot of reviews don’t even take into account when comparing video cards frames that are generated via ASW and those that are fully rendered. Heck I see reviews where frames are regularly dropped but the absolute FPS is still high and they say there are no differences when really there are significant differences.



Hi there. This is Sean, the author of that article. I wasn’t happy with the result and felt I could dig deeper. Just finished Part II:

I found SPS having a massive impact this time, and my first article is getting edited to reflect that.

Kind Regards.


Very interesting read. Thank you for sharing.

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Thank you. Trying to do some of the most in-depth and accurate VR testing possible. :sunglasses::+1:

Sean Kaldahl - VR Sim Contributor


Thank you for continuing to research this. Looks to me like 10%-40% improvement, which is potentially very helpful indeed. One day, it would be nice to get that kind of benefit with DCS World…

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Have you tried this? https://www.reddit.com/r/hoggit/comments/i7zmug/dcs_performance_improvement_frustum_culling/?utm_medium=android_app&utm_source=share

It seems to me that this might be sps, but I’m not 100 % sure. It looks like the video creator describes something else, but at the command in the autoexec file is options.graphics.stereo_mode_use_shared_parser = true.

I’ve tried it and it seems to bring my frametimes down, with some minor pop in in my far left.

I read on ED forum that this is work in progress which would suggest it’s going to be an option at some point.


Very interesting, I will try that!

Doesn’t seem to be SPS, but it may be even more interesting. Also, while I have been able to get foveated rendering, both through PiTool and the Shaders Mod, this seems to be different from that as well.

If Eagle Dynamics is finally ready to start working on DCS World performance optimizations, that is great news.

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I just tried it on and off in a repeatable situation. Without this option I had cpu spiking to 94 percent at a point with much geometry present, las vegas, airport and quite a few planes parked. Stuttery. Tried the same with the option on and I got a dropped frame, but nothing more. Cpu increased a bit, but not as severe as with the option off. More testing needed to be sure, but I’m not that familiar with good testing scenarios in dcs. Still seems like it works to some degree. By the way, do you prefer the shader mod or the pitool foveated rendering?


WOW. This could be phenomenal. Reducing the CPU load in DCS World.

By the way, do you prefer the shader mod or the pitool foveated rendering?

Shader mod. PiTool foveated rendering trades a few ms GPU load for about the same CPU load, which on balance is usually unhelpful. PiTool also shows the instrument backlight texture at the edges (big bright green), which is obviously not acceptable for night flight.

Thanks, I’ll stay with the shader mod then!

I have enough experience with vr to know that my quick testing might not cut it, but that was all I had time for today. It might be an indication of good things to come. Still wondering if it is sps. I’ve read that eagle dynamics do not want to use proprietary tech in dcs so that is an argument against it being sps. Please share your experience once/if you try it out.

Also if you have a good test scenario let me know. My experience with dcs is that I can have periods of stable cpu and gpu load and suddenly it spikes in certain situations.

edit: I had to try the same scenario once again. Now I’m not so sure it helps as much as I earlier said. I’ll withhold any conclusions for the time being. If anyone is into dcs try it and see if it helps.

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