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Valve's Michael Abrash: Latency is getting in the way of VR

15 or even 7 ms could be upper limit for believable tech, says developer

Valve's Michael Abrash has poured cold water on the idea of an imminent future containing believable virtual and augmented reality systems, writing that current limitations on latency are the bottleneck to future development.

Writing on the Valve Blog, Abrash discussed the problems caused by the delay between user input and display response, which causes particular problems in virtual and augmented reality systems because of the nature of the interface.

"Assuming accurate, consistent tracking (and that's a big if, as I'll explain one of these days), the enemy of virtual registration is latency. If too much time elapses between the time your head starts to turn and the time the image is redrawn to account for the new pose, the virtual image will drift far enough so that it has clearly wobbled (in VR), or so that is obviously no longer aligned with the same real-world features (in AR).

"How much latency is too much? Less than you might think. For reference, games generally have latency from mouse movement to screen update of 50 ms or higher (sometimes much higher), although I've seen numbers as low as about 30 ms for graphically simple games running with tearing (that is, with vsync off). In contrast, I can tell you from personal experience that more than 20 ms is too much for VR and especially AR, but research indicates that 15 ms might be the threshold, or even 7 ms."

Abrash continues to examine the problem in more detail, before coming to the conclusion that current minimum latency is around 36ms: "a long way from 20 ms, and light-years away from 7 ms."

"Short of racing the beam, there is no way to get low enough display latency out of existing hardware that also has high enough resolution, low enough cost, appropriate image size, compact enough form factor and low enough weight, and suitable pixel quality for consumer-scale AR/VR.

"Someone has to step up and change the hardware rules to bring display latency down. It's eminently doable, and it will happen - the question is when, and by whom. It's my hope that if the VR market takes off in the wake of the Rift's launch, the day when display latency comes down will be near at hand."

The Occulus Rift, which completed a highly successful Kickstarter campaign last year, hopes to reinvigorate virtual reality when it launches in early 2013. For an insight into the device, read our interview with inventor Palmer Luckey here.

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