In AR pass-through mode, the ZED Plugin for Unity continuously compares data from the ZED Mini IMU against the position of the VR headset. This is used to compensate visual latency and better align virtual VR controllers on their real-world counterpart.
However, there are cases where the IMU's orientation and the headset can get permanently out of sync. This causes the tracking to shake as it tries to correct the error. This makes it appear as if the objects themselves are shaking, but it's actually the position of Unity's in-game Camera.
This issue can happen if:
- The mount for the ZED Mini was not properly attached to the headset.
- You are using a headset for which we don't offer a mount, and did not center it properly - particularly if the front of the headset is curved.
- The mount on the headset is loose and shifts at runtime.
- Rarely, the ZED Mini's IMU may have a calibration issue.
If this is the source of the problem, then you will see sharp movements constantly, even if the headset is still and there is nothing moving in your environment. Sometimes the issue can start after a minute or two into running your scene.
Correct Alignment Issues
If one of the above points is true, then the best solution is to reposition the ZED Mini as necessary to fix its alignment. This should not only solve the tracking issues, but improve the pass-through experience as well.
If using an Oculus Rift or HTC Vive, make sure the mount aligns well with the included mounting template sticker. If you need replacement mounts or templates, you can purchase them as part of our VR Kit. If using a Vive Pro, you can download a 3D-printable mount for it in STEP or STL formats.
If using another headset, make sure that the ZED Mini is facing straight forward, and is adhered strongly enough that it won't move at runtime. If you make either of the above adjustments, run your scene for a few minutes while the headset is on a flat surface.
Disable Offset Check
The Unity plugin sets the HMD's rotation as a "prior" for the ZED Mini's IMU. Commenting out the line where this happens will remove the tracking issues.
In ZEDMixedRealityPlugin.cs, go to the AdjustTrackingAR() method and comment out the following line (line 603 as of writing):
zedCamera.SetIMUOrientationPrior (ref latencyPose.rotation);
This should solve the problem immediately. If not, your ZED Mini is likely rotated significantly off-center. It's better to adjust the camera's physical position to solve this, but if you can't, then go to the InitTrackingAR() function and comment out this line (line 554 as of writing):
If neither Option 1 or Option 2 helps you, send an email to firstname.lastname@example.org with details.