Angle measurement by Joints Orientations

Hi, I am working on an application where I want to measure the angles of extension, flexion, abduction and adduction.
I do have an Intel real sense D415. I am wondering if anyone knows a way to measure the angles of the arm by just using the joint orientation values. I am thinking measuring with quaternions to euler angles is the way to go, as by doing the scalar factor of 2 vectors some angles and arm variations aren’t taken into consideration.

Hope someone gives me an idea on how I should go on this one.

Hello Sergio Morancho!

To determine the bend angle, we need the coordinates of three reference points,
for example, the elbow is necessary to know the position of the joints: elbow, shoulder, and wrist.

To calculate the angle value, you can use the Vector3.Angle method for two vectors:
from the shoulder to the elbow and from the hand to the elbow.

Here is an example of a method for calculating the angle in degrees:

``````float Angle(nuitrack.Skeleton skeleton, nuitrack.JointType targetJoint, nuitrack.JointType parentJoint, nuitrack.JointType childJoint)
{
Vector3 targetPosition = skeleton.GetJoint(targetJoint).ToVector3();
Vector3 parentPosition = skeleton.GetJoint(parentJoint).ToVector3();
Vector3 childPosition = skeleton.GetJoint(childJoint).ToVector3();

return Vector3.Angle(parentPosition - targetPosition, childPosition - targetPosition);
}
``````

Let me know if there’s anything else I can do for you.

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