![]() Concretely, we know that the headset has a (claimed) combined horizontal FoV of 200°, that its display panels are 120mm wide (3840 pixels at 806 ppi), and that the two screens are angled with respect to each other. Nonetheless, we can still investigate the principles by creating a reasonable model of the headset based on known specifications. In other words, understanding how a concrete VR headset, such as Pimax 8k, does its projection requires knowledge of its internal geometry, which is something we don’t currently have. If the geometry is represented accurately, and the projection done correctly, the illusion will hold. The way to fulfill this requirement is to project virtual objects onto a headset’s screens using the headset’s internal geometry, i.e., real-world sizes of its screens, and their real-world position and orientation relative to the viewer’s eyes. ![]() If this is not done correctly, virtual objects, including the entire virtual environment, will not appear stable, causing a break of immersion or even nausea. If this is done correctly, virtual objects appear in the correct places, and do not appear to shift, warp, or stretch as viewers move around or rotate their heads. As our brains don’t naturally work in Cartesian coordinates, this requirement can be rephrased using polar coordinates: If an object is supposed to appear, from the viewer’s current position, at angles of (φ, θ) relative to the viewer’s current gaze direction, then it should appear at those same angles inside the headset. Boiled down to its essence, this means that if any virtual object is supposed to appear at a certain position (x, y, z), the viewer should see the same object at those same coordinates. ![]() To understand the issue with geometric distortion, we briefly need to recap what VR is supposed to do: create a virtual environment that looks real, in some meaning of that word, to the viewer. (Probably not 100% true, as this appears to be a frame submitted to SteamVR’s compositor, which subsequently applies lens distortion correction.) At least, if one ignores lenses and lens distortion, which is what I will continue to do for now.įigure 1: Frame as rendered to one of the Pimax 8k’s screens, according to the Kickstarter campaign. On the contrary, this is what a frame rendered to a high-FoV VR headset should look like. The problem is that the frame looks obviously distorted, but that this obvious distortion is not what the reviewers were complaining about. 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 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. Instead, I want to focus on one particular issue that’s causing a bit of confusion and controversy at the moment.Įarly 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). 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. 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.
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