The following excerpt describes an interesting technique to enable higher resolution on the headset without using brute computing power to drive 4K@120fps per eye. Although there are tradeoffs to using it, techniques like this will continue to improve and help drive HMD capabilities to the next level where resolution will eventually become a non-issue.
All that aside, how exactly do Pimax expect people to drive two sets of 4k displays at higher enough refresh rates needed for good, low latency VR? Enter ‘Brain-warp’. Brain-warp is a technique where you render and display an image to one eye only, and then render and display for the other eye, in a sequence such that one eye is seeing an image and the other isn’t at any given moment in time. This way, they’re actually rendering a single 4K image at 120 times a second, but the user perceives it as a complete 8K image at 120Hz. How? Because that frequency is high enough that we don’t perceive that one eye is blind while the other isn’t, at least for a tiny fraction of a second. It’s like raising one hand to one eye, lowering that hand and raising your other hand to your other eye, and doing that very so fast that you simply don’t notice it. Active-shutter 3D glasses use the same concept, often at the same 120Hz refresh rate.
Brain-warp is a neat trick then, but not without its downsides and clearly there’s still a huge amount of power needed to drive the displays in this headset. To output 4K at 120Hz, they say you’ll need at minimum an NVIDIA GTX 980 but that’s assuming Async Timewarp is also in play helping resolve dropped frames. Their actual recommended specification however is either dual GTX 1070s, or one GTX 1080.
Another caveat here is that brain-warp also requires “very accurate synchronous fine tuning” according to them, and results in a “ghosting” artifact that appears during motion. That artifact wasn’t very distracting to me in the demo, but it may be more distracting at higher brightness levels or other scenarios.