Understanding angles in analyze_skeleton format

Usage & Issues
#1

Hi , I was able to extract the skeleton angles defined in the config file. However I have some problems understanding it. Taking example for the horse poses.

For example I was interested in the in the Elbow angle , that is between (nearknee, elbow, Stifle) combination, How can i find that angle ? IF understood it would be something like

angle between vector(stifle-elbow) vector (knee -elbow) . However the sample output i get is as follows . It feels i am doing something wrong here . What could be the problem ?

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Analyze_Skeleton - angles that bones create
#2

For all segments, angles are expressed relative to a horizontal line (and positive when counter-clockwise by convention). To obtain the desired joint angles, you’d need to subtract one from the other. Have a look at that post too from the original author of analyzeskeleton :slight_smile:

#3

Thanks @jeylau , so i undertand now that they are just relative in space. So for calculating the elbow angle i can do the following

elbow_angle = elbow_stifle - nearknee_elbow (for each frame)

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1 Like
#4

Hi am i to understand correctly that the angle , measured clockwise with reference to horizontal plane , is the one shown in figure 1 ? (Angle A - the acute angle)

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#5

The angle tells you by how much you would have to rotate that horizontal line anticlockwise so that it matches the bone orientation. That’d be angle A in fig1 and 180 + angle B in fig2.