2,725
edits
Changes
→How Does It Work?
==How Does It Work?==
[[Oculus Rift]] uses the [[IMU]]s as the primary positional tracking system. It responds extremely quickly and updates at several hundred Hz (1000Hz sampling, 500Hz reporting). However, IMUs drift due to double-integration of error. The drift is on the order of meters per second. So Constellation do is squelch that error 60 times per second (both have a 60Hz global position update rate) using their optical sensors to provide an absolute position reference.
For Constellation, high-speed position tracking performance is down ENTIRELY to IMU performance. It wouldn't be possible at all without another absolute reference system (optical, magnetic or otherwise) but it's the IMU that's doing the grunt-work.
Constellation's [[external camera sensor]] is genlocked; they capture a frame at the same point in time. That means all marker positions are known at the exact same time. As for Constellation having a 'smearing' issue: Commercial optical MCAP systems do not generally use active markers (though some do), but retroreflective markers and an illumination system adjacent to the camera lens. These relative dim markers are still easily discriminable in all but the harshest (e.g. outdoors in direct sunlight) conditions. If you're being clever with your blob tracking, you can even use the blob shape from the smear in order to provide an instantaneous velocity measurement, though it's generally just easier to drop the shutter speed and make your markers brighter.
==References==