Stablize head rotation movement using Kalman filter

[henryouly]

We need to filter the rotation vector from SolvePnP to reduce subtle movement. When using webcam, the movement looks more verbose.

[henryouly]

It seems Kalman filter can be only applied to vectors, not quaternions.

There’s a discussion thread here: https://math.stackexchange.com/questions/2621677/extended-kalman-filter-equation-for-orientation-quaternion

There’s a paper to apply that to quaternion-based orientation tracking: https://kodlab.seas.upenn.edu/uploads/Arun/UKFpaper.pdf

[henryouly]

More understanding of the problems:

• https://github.com/DangLamTung/Quaternion-Extended-Kalman-Filter/blob/master/ekf.pdf
  • Code: https://github.com/DangLamTung/Quaternion-Extended-Kalman-Filter
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6339217/
• https://www.youtube.com/watch?v=YbhUdnTHcMo