There is an on-going, but already highly successful, Kickstarter campaign for a new VR head-mounted display with a wide (200°) field of view (FoV): Pimax 8k. As I have not personally tried this headset — only its little brother, Pimax 4k, at the 2017 SVVR Expo — I cannot discuss and evaluate all the campaign’s promises. Instead, I want to focus on one particular issue that’s causing a bit of confusion and controversy at the moment.
Early reviewers of Pimax 8k prototypes noticed geometric distortion, such as virtual objects not appearing in the correct places and shifting under head movement, and the campaign responded by claiming that these distortions “could be fixed by improved software or algorithms” (paraphrased). The ensuing speculation about the causes of, and potential fixes for, this distortion has mostly been based on wrong assumptions and misunderstandings of how geometric projection for wide-FoV VR headsets is supposed to work. Adding fuel to the fire, the campaign released a frame showing “what is actually rendered to the screen” (see Figure 1), causing further confusion. The problem is that the frame looks obviously distorted, but that this obvious distortion is not what the reviewers were complaining about. On the contrary, this is what a frame rendered to a high-FoV VR headset should look like. At least, if one ignores lenses and lens distortion, which is what I will continue to do for now.
Figure 1: Frame as rendered to one of the Pimax 8k’s screens, according to the Kickstarter campaign. (Probably not 100% true, as this appears to be a frame submitted to SteamVR’s compositor, which subsequently applies lens distortion correction.)
