Drift in VR trackers: what it is, why it happens and how to avoid it
By madKoding · Published on
If you use full body trackers with motion sensors, sooner or later you will run into drift: your avatar faces the wrong way, a leg ends up rotated or your body slowly "wanders". It's normal, it has an explanation and it can be reduced a lot. Here's how.
What is drift?
IMU trackers (like madTrackers, SlimeVR and most trackers without base stations) compute their orientation by adding up what the gyroscope measures, many times per second. Each measurement has a tiny error, and those errors accumulate. Over time, the tracker believes it is rotated a few degrees more than it really is: that's drift.
It is most noticeable on the horizontal rotation (which way the tracker faces), because gravity corrects tilt but not heading.
How often does it happen?
It depends mostly on the sensor. As a reference, with the sensors used by madTrackers:
| Sensor | Typical time before noticing drift |
|---|---|
| LSM6DSR | ~20 min |
| ICM-45686 | ~45 min |
| LSM6DSV | ~45 to 60 min |
| ICM-45686 + magnetometer | ~60 min |
These are typical values: temperature, how you move and calibration all change them.
8 ways to reduce drift
- Do a full reset when you start. Standing straight, arms at your sides, facing forward. In madTrackers Server it's the first calibration step.
- Use the orientation reset during your session. When your body starts rotating on its own, an orientation reset fixes the heading in seconds. Bind it to a shortcut.
- Leave automatic correction enabled. madTrackers Server ships with automatic drift correction enabled by default, so manual resets become much less frequent.
- Let the trackers warm up. Sensors behave slightly differently with temperature. Turn them on a couple of minutes before calibrating.
- Don't move them while they boot. Leave them still on a flat surface for a few seconds before putting them on.
- Tighten the straps. A tracker that slides or bounces makes the software see movement that isn't there.
- Stay away from magnets and large metal. If your tracker has a magnetometer, speakers, magnets or big metal structures can disturb it.
- Keep the firmware up to date. Each firmware release improves sensor fusion filters. Update from the firmware page.
Drift vs other problems
- Legs or torso are twisted from the start: that's mounting, not drift. Repeat Mounting calibration and then a full reset.
- A tracker freezes or jumps: usually signal or battery. Check the signal indicator in madTrackers Server and make sure the receiver isn't hidden behind the PC.
- A tracker says "Needs reset": it came back after losing signal; do an orientation reset.
Do Vive Trackers drift?
Vive Tracker 3.0 uses laser base stations, so its position doesn't drift like an IMU. In exchange it needs base stations, a PC and a clear line of sight, and costs considerably more. For most VRChat users, a modern IMU with automatic correction and an occasional reset is a very good trade-off. More detail in the VR tracker comparison.
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