The Economist explains VR. Here are some highlights:
"Humans have stereoscopic vision, which means that they perceive depth by noting the subtle differences between the images received by each of their eyes," says the article. "VR headsets have two tiny screens, one for each eye, which exploit that. By carefully altering the images fed to each eye, the user's brain is persuaded that it is looking at an entire three-dimensional world instead of a pair of flat images.
"The next trick is to make it seem as if that world surrounds the user. Modern VR headsets are fitted with tiny sensors similar to those used in smartphones—accelerometers, gyroscopes and the like—which let them keep track of the movements of the wearer's head. When the user looks around, the computer can update the view on the screens. But those sensors must update themselves dozens of times a second, and errors accumulate quickly.
"For VR to work, the illusion must be extraordinarily slick. Humans are extremely sensitive to visual inconsistencies; even small snags can cause "VR sickness", an affliction like motion-sickness. So images must update very quickly. That requires beefy computing hardware capable of generating 90 or more frames of animation a second (standard TV, and most video games, target only 30 updates per second). And the sensors that track the user's head must be able to talk to the computer at least that fast: any delay can cause an unpleasant dragging sensation."