Note: we could achieve 80% foveated reduction in GPU cost if we just had two improvements...

Based on some previous math seen here, I then thought about what performance improvement we could achieve if we solved two key problems. The first is slippage, as discussed in the link and paper. The second is rendering pipelines. Right now foveated rendering is mainly being achieved, in the case of VRSS by Nvidia, through an MSAA mechanism, which means that the performance improvements only apply to rasterization, not shading. If we could have it apply across the board, then we could truly say there's an XX% performance improvement on the GPU for the same visual quality.

So let's assume we've solved those problems, and we're using the "safety margins" as discussed in the link, what would be that XX%?

Abrash mentioned once that it's theoretically possible to reduce the amount of pixels we have to render by about 95% with foveated rendering. So with a maximal amount of 5% of pixels needing to be rendered, and a foveal region + safety margin of 12 degrees, then we might need 20% of pixels rendered. This is because the foveal region is 6 degrees, so doubling that means doubling the radius of the circle we have to render. But doubling radius means quadrupling surface area (SA equals pi times radius squared). Therefore, if we had 5 pixels out of 100 that were rendered, now we need about 20 pixels. This assumes that the fovea is in fact where almost all the pixels are located.

So we get to 80% reduction. It would likely be a bit worse in a real world headset, because other factors may cause a need for a larger safety margin, but if we do things really well, then we might be able to get close to 80%. That's a pretty big deal (even if it's not 95%). The question is how long it'll take to get to that level of eye tracking technology, and development of new rendering pipelines.

However since Abrash's 95% estimate was with regards to the human visual system, which has a much larger FOV than current headsets, this calculation would also need to assume that the eventual headset it's released on is a headset that's near the limits of human FOV, which might be possible by the time rendering pipelines and eye tracking both get ready. If at least eye tracking can get ready though, a rough calculation assuming a 110 degree headset gets us to 60% of performance cost reduction in rasterization. Not bad. The difference between that and what's achievable today with current eye tracking headsets like Vive Pro Eye may in fact be due to the slippage problem.

This may have further implications on wireless foveated transport as discussed in older notes. That is, we would be waiting on rendering pipeline and eye tracking improvements, to get us to 80% or more, such that it makes lossless and +1 ms latency wireless streaming on WiFi possible. Lossy and higher latency streaming may be successful sooner as we now have improved Virtual Desktop and soon probably Air Link. We may also accept a wire in some cases. That will be a transition period, before full foveated transport over WiFi can happen.