Relativty: An open-source VR headset for $200

From the GitHub this is only capable of 3DoF tracking, which puts it in the same category as the defunct Oculus Go headset, or Google Cardboard. 6DoF is really the bare minimum to qualify as proper VR nowadays.

For the uninitiated 3DoF means the headset only tracks the rotation of your head, not your heads absolute position as you move around, while 6DoF tracking does both. 6DoF is also much harder to implement.

Never understood why my GCardboard couldn’t do that, my phone sure has a bunch of accelerometers and giros. Sure higher and other techs can track better but isn’t it enough for a basic sense of mouvement? For most of the applications I won’t more than a few meter anyway.

Probably some have tried and I’ll be curious to know what prevent it.

The problem with accelerometers and gyros is they drift badly if you try to derive absolute positioning from them alone. They need to be fused with some other form of tracking to anchor them in absolute space, which in the case of the Quest and Vision Pro is done with multiple outward-facing cameras fed into a SLAM algorithm.

Maybe Cardboard could have attempted to use the phones camera for SLAM, but a single lens would only have got them so far. Dedicated VR headsets have at least four cameras pointing in different directions, which are sometimes augmented by IR projectors and/or LiDAR.

Lots of quadcopter flight controllers use 9DOF IMUs , with 3 gyros, 3 accelerometers, and 3 compasses. The absolute directional data from the compasses solves (at least most of) the angular/gyro drift.

The translational drift is harder for VR/AR headsets indoors. Drones can do sensor fusion with GPS and the accelerometers to solve translational drift from the accelerometers (or, for FPV drones, they just let the meatware compensate).

The "9DoF" in IMU datasheets is a marketing term, they just add up all the sensor dimensions they have. Some IMU modules talk about "10DoF" , because they have added a barometer to it.

So even a good "9DoF" IMU is not usable for 6DoF VR, as it still drifts way too much. Sadly the magnetometer in the IMUs suffers from all the magnetic fields generated by the rest of the electronics around it.

This might also be one of the reasons why 9DoF IMUs are increasingly rare on the market.