GPU Performance Scaling

Another great data point that FCAT VR can provide us is the ability to see the value (or not) in higher cost GPU purchases towards VR gaming experiences.

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In Edge of Nowhere, we can see the impressive frametime drop that the GeForce GTX 1080 offers over the GTX 1060, dropping from 6-8ms to 4-6ms.

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In this instance, the added performance doesn’t really help the gamer as both GPUs can easily provide a solid 90 FPS of delivered frame rate. In this instance, spending the added money on the GPU doesn’t add to the experience. However, if we look at the unconstrained FPS, a metric generated by FCAT VR that tells us what FPS we COULD run at it we were not limited by 90 Hz screens and Vsync, we see the scalability of each GPU.

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While these potential frame rates are much higher than we need today, it does show the GTX 1080 to have a 49% better potential to improve VR performance in this game/engine/etc. That can help give us guidance on the “future proof” nature of a card like the GTX 1080, that will improve VR gaming in future headsets with higher resolution screens, higher refresh rates, or in titles that allow us to adjust image quality settings.

Here is another example with Chronos.

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When running at the Epic quality preset, the GTX 1080 easily outpaces the GTX 1060, as you would expect. Frametimes are in the ~11ms range for the higher end card but reach as high as 20ms+ with the GTX 1060.

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And the interval plots bear that out. The GTX 1080 can maintain a nearly perfect 90 FPS throughout our gaming in Chronos at those settings. The GTX 1060 spends most of its time in the 45 FPS / space warp zone.

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If we look at the unconstrained FPS results, the GTX 1080 is theoretically capable of reaching a frame rate of 118 FPS while the GTX 1060 is only at 70 FPS, a difference of 40%.

Finally, let’s look at Dirt Rally.

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Here you see that the frametimes for both configurations are fairly close, but note that the GTX 1080 is running at the Ultra preset while the GTX 1060 is only running at High.

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Both show consistent 90 FPS gameplay in our interval plots, resulting in high quality gaming experiences for the user.

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This bar graph might be a bit more confusing – but stick with me. When the frame rate of the game is right at or just below the 90 FPS mark, the calculated unconstrained frame times can be…funky. Because the frametimes reported by the Oculus and SteamVR runtimes combine the CPU and GPU, but the unconstrained time is based on GPU alone. In situations where the frametime is very close to the 11ms/90FPS mark we see overlaps of CPU and GPU time (rather than it being purely sequential). The result is that unconstrained FPS will sometimes be lower than delivered FPS. 

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