Nvidia has researched in temporarally stable resoultion reduction at the edges (needed or you'll notice flickers in the blurring) as well as enhancing contrast which the eye is more sensitive to in the peripheral vision than sharp details.
Put a lot more research into this as well as proper support in the major 3D game engines and we have a winner.
Current lenses have quite a pronounced sweetspot in the centre of the vision so high resolution is wasted at the edges.
"fixed foveated rendering" is supported with Oculus and implemented directly in some games to reduce resolution at the edges just without eye-tracking so you can notice it if you move your eyes instead of your head. There is also "dynamic fixed foveated rendering" to ramp up/down for the current rendering load.
It had a pair of Silicon Graphics Reality Engine IIs, one projecting a lower res image over the entire half-spherical screen, and the other driving a projector mounted on a gimbal that tracked the flight helmet - to display a high resolution image in the direct field of view of the pilot.
It was _possible_ if you tried, to "trick" the system so you could notice from the pilots seat what it was doing. But it was _remarkable_ the difference between sitting in the seat with the helmet on, and watching from behind where you could really obviously see the high res patch of sky moving around. Enemy planes turned from Space Invaders kind of pixel art into recognisable Russian fighter planes when the pilot looked at them. The "immersive reality" while flying the sim was amazing.
I've only used Quest 1, with _fixed_ foveated, and while it's noticeable, it's good enough that I could see a generation or two of improvement pushing it beyond noticeability.
This seems to be describing foveated rendering, which is reducing the image quality in your peripheral vision, because you are less likely to notice it there. It requires tracking where the eye to so you know what part of the screen the eye is looking at.
The RTX 3090 is likely rendering the whole 8k screen at a consistent quality level, whereas foveated rendering would mean that only the part of the display that the eye is actually focused on would be rendered at full quality. If Apple could pull off the tracking well enough (accurately, with low latency), they could probably save a lot of GPU power by lowering render quality outside of what you're looking at.
b) VR uses variable rate shading because we have a lower visual acuity in our peripheral vision.
c) VR rendering typically "shares" a significant amount of the work between the two viewports. E.g.: one set of "commands" are rendered simultaneously into two buffers with different view transforms. Textures and meshes are cached once and rendered twice, so the bandwidth requirements aren't actually doubled.
d) Display stream compression (DSC) and similar technologies would work well for VR because the viewport is always in motion with a high refresh rate. One could even imagine sending a H.265 compressed stream wirelessly at a mere gigabit, which is fantastically high bitrate video but well within current WiFi capabilities.
e) There will be future developments as well, we're not stuck with current technology. Keep in mind that current era flagship GPUs are manufactured on silicon processes that are about 3 generations old! By the time this VR kit hits the mainstream market, GPUs could be manufactured on a 3 nm TSMC process and easily put out 90fps in 8K resolution.
It'd also explain the price tag, if you have to buy both a high quality display and a speedy GPU that's been glued together.
Also, it sounds like this would be more of an all-in-one device, where it’d handle the rendering instead of connecting to a separate computer, so the rendering performance is more likely to be the limitation than any kind of transmission limitations anyways.