Foveated Rendering performance advantage on Quest Pro

Quest Pro supports Eye Tracked Foveated Rendering, but exactly how much does it improve performance?

If you’re not familiar with the term, eye-tracking foveated rendering (ETFR) is a technique where only the region of the screen you’re currently viewing is displayed at full resolution, freeing up performance because the rest is at a lower resolution. That extra performance can be used to improve the graphical fidelity of applications or for a higher native resolution.

You don’t notice the lower resolution in the periphery because only the human eye can see high resolution in the very center – the fovea. Because of this, you cannot read a page of text without moving your gaze. Believe it or not, that foveal area is only about 3 degrees wide.

ETFR has been under consideration for a long time “holy grail” for VR, because if your GPU really only had to render 3 degrees of your field of view at full resolution, the performance advantage could be 20x. This would allow for ultra high resolution displays or incredibly detailed graphics. But in reality, achieving this would require perfect eye tracking with zero latency, absurdly high screen refresh rate ia high-quality reconstruction algorithm so you don’t notice flickering and shimmering.

The Quest Pro is Meta’s first headphone to ship with eye tracking. The end-to-end latency of this first-generation eye-tracking technology is on the order of 50 milliseconds, and the screen refresh rate tops out at 90 Hz. As such, the actual savings from plotting it in letter form is nowhere near 20x.

Meta headsets are supported Fixed Foveated Rendering (FFR) – showing edges lens in a lower resolution – than the Oculus Go six years ago. U conversation given to developers this week, Meta detailed the exact performance benefits Eye Tracked Foveated Rendering (ETFR) and compared it with FFR.

Both types of aperture rendering are enabled by the developer for each application (although obviously both cannot be used at once). Developers are given three choices for reducing peripheral resolution: level 1, level 2 and level 3. With ETFR level 1 the peripheral is rendered with 4x fewer pixels, while at level 3 it is generally 16x fewer pixels.

The exact performance benefit of foveated rendering also depends on the native resolution of the application. The higher the resolution, the greater the savings.

In Meta’s performance testing application, they found that at standard resolution, FFR saves between 26% and 36% of performance depending on the level of foveation, while the new ETFR saves between 33% and 45%.

But at 1.5x standard resolution the savings were greater, with FFR from 34% to 43% and ETFR from 36% to 52%. That’s up to a 2x increase over using without foveation – but only a small advantage over FFR.

Of course, what really matters is what we don’t know yet: how noticeable are each of these ETFR levels? And how does this compare to observable FFR? This is what needs to be compared – not given the level of FFR with the same level of ETFR. This is something we’ll be testing in depth for our Quest Pro review.

On Quest 2 FFR level 1 is not noticeable at all, but level 3 definitely is. And since Quest Pro has sharper lenses both in the center and at the edges, FFR can be more noticeable than ever before, making ETFR even better.

On PlayStation VR2, the claimed performance advantage of foveated rendering is greater. Sony claims its FFR saves about 60%, while its ETFR saves about 72%. This is likely due to the vastly different GPU architectures of console and PC GPUs compared to mobile GPUs, as well as the higher resolution. It could also be due to differences in eye tracking technology – Meta is in-house while Sony is uses Tobii’s.

Eye tracking on Quest Pro and PlayStation VR2 is optional for privacy reasons. But disabling it will obviously disable ETFR as well, so apps will have to fall back to FFR.