I am using Google Mediapipe Body Pose estimation to detect body pose landmarks and to calculate the 3 angles in the shoulder joint with respect to XYZ axis when point 13 moves. The z-axis is a scaled value referenced from the center of the hip. The angle between point 11 and point 13 are required to be calculated. I tried the approach using the method stated in the following link

https://math.stackexchange.com/questions/2736426/how-to-find-three-angles-of-a-point-in-3d

but the result were not as expected. I also tried using the vector dot product but by using 2D points that the three axes in pairs i.e. XY, XZ and YZ. This approach also failed. Is there a way to calculate these three angles at point 11 with respect to movement of point 13.

Any help and guidance is appreciated.

Best Regards

Fawad