Body Angles in Body Tracking

Software Python
1

How are the angles in the body tracking module calculated?
Are the angles calculated from the position of the points according to each other, or is it the angle of these coordinate systems according to each other?

2

Hi @zedev,

The orientations are relative to the parent keypoint.

3

Yes, I have read what you said. But what are the calculations here? For example, there are 3 different angle values for the shoulder. Is a coordinate system assigned to the keypoints, and is a calculation made based on that? Or is it approached from the points? I need to understand this for my research.

Thank you.

4

Hi @zedev

The rotations are indeed dependant on the positions of the keypoints. That’s why the keypoints at the extremities will not have an orientation set.
The rotations are given in the coordinate frame given in the InitParameters.

Sorry I was not clear before :slight_smile:

5

Is a predictive algorithm used or are mathematical operations applied when calculating joint angles? I want to understand the logic behind the angle calculation process. I need biomechanical joint angles for my work, and I need to ground the angle calculation process for a study I will conduct. I have found angle values using various algorithms, but they don’t match the values provided by the SDK.

Thank you.

6

position_orientation.csv (6.1 KB)

For example, the angles I calculate from the 3D points in the annex are not the same as the angles given by SDK. Is there a mathematical error?

Thank you.