Finding Joint Angle from Motion Capture
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Mary
am 12 Dez. 2012
Kommentiert: Suranjita Ganguly
am 23 Jun. 2020
Hi!
I'm working right now with data from a motion capture device, essentially picking up data for three markers placed on the head neck and shoulder in an x y z plane.
My difficulty trying to develop a code to calculate the joint angles between these three markers. I am able to animate the three coordinates to play as an animation, but I'm more interested in the calculation of the angles between these points changing over time.
Any ideas on how to go about this?
Thanks
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Roger Stafford
am 12 Dez. 2012
At any time, let H = [x,y,z], N = [x,y,z], S = [x,y,z] be coordinate vectors of the head, neck, and shoulder markers at that time. Then the three respective inner angles within the triangle HNS then are:
h = atan2(norm(cross(N-H,S-H)),dot(N-H,S-H));
n = atan2(norm(cross(S-N,H-N)),dot(S-N,H-N));
s = atan2(norm(cross(H-S,N-S)),dot(H-S,N-S));
(The sum of these should always be pi to within round-off accuracy.)
Roger Stafford
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Mousumi Nag
am 24 Jan. 2017
Can I get back the S,N,H from the angle .In other words, How can I get the vector points where angle is given
Suranjita Ganguly
am 23 Jun. 2020
The sum of the angles should be Pi (approx), because the three angles are forming a triangle, and sum of all internal angles in a triangle is 180 degrees i.e. pi
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