An expert look inside the HTC Vive's positional tracking system

- VR developer Oliver Kreylos.

Valve's publicly-available OpenVR SDK just hit v. 1.0.0, and now longtime VR expert and enthusiast Oliver Kreylos has used it (along with an HTC Vive Pre devkit and his own testing utility) to evaluate the accuracy of Valve's Lighthouse positional tracking system.

 He shares some of his findings in a blog post published today, and it's well worth reading for any VR developers curious to learn more about how Lighthouse's laser-based tracking works or how it compares to more traditional camera-based systems. 

"Not surprisingly, there is a lot of wild speculation and misinformation about Lighthouse’s update rate floating around," writes Kreylos. He goes on to try and explain how the Lighthouse base stations work by sweeping the tracked area with lasers on a 8.333ms cycle, and how he's learned (by directly interrogating the Lighthouse driver's code) that they're actually delivering positional tracking data at n even faster clip via making a "best guess" based on raw tracking data.

"This means that at OpenVR’s internal interface, worst-case latency for head tracking data is about 1ms, and worst-case latency for controller tracking data is about 2.7ms, assuming that wire(-less) transmission and pose calculation add negligible latency," Kreylos notes, adding that the tracking data is delivered to applications at a slower rate via vrserver. "At vrserver’s client/server interface, on the other hand, worst-case latency is 4.444ms and 4ms, respectively."

Kreylos is careful to note that all of his findings are based on his own independent testing, and that some of his measurements don't match up with what some Valve employees have told him. You can (and should) read his full post for a more thorough, highly technical deep dive into some of the nitty-gritty details of the Vive's Lighthouse tracking system.