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 cmeans 04-05-2015 07:31 PM

3 Attachment(s)
I'm a beginner to Vizard. I'm trying to write code that will recognize when the user has their right arm in a right angle. I'm using vizmat.AngleBetweenVectors() to try and get the angle between the right shoulder and the right hand. To my mind, if you hold your arm at a right angle, it will read ~90 degrees.
I'm encountering two problems:
1) As I move my arm back and forth, holding it at a right angle, the degrees change.
2) It's not reading 90 degrees.

Here is my code:
Code:

```def RightArmAngle():     RShoulder = vrpn.addTracker('Tracker0@localhost',RIGHTSHOULDER)     RSpos = RShoulder.getPosition()     RHand  =vrpn.addTracker('Tracker0@localhost',RIGHTHAND)     RHpos = RHand.getPosition()     RHvec = viz.Vector(RHand.getPosition(),normalize = True)     RSvec = viz.Vector(RShoulder.getPosition(),normalize = True)     RAVector=vizmat.AngleBetweenVector(RSvec,RHvec)#RAVector and RAAngle return the same value     RAAngle = vizmat.AngleBetweenVector(RSpos,RHvec)         print("r elbow:",RHvec)     print("r shoulder:",RSvec)         print("position Angle:", RAAngle, "vs RAVector",RAVector)     print("new")         vizact.ontimer(1,RightArmAngle)```
Here are some diagrams and my outputs:

Attachment 694
Raised Arm, Turned to Side. Vector Returned: ~31
Attachment 692
Right-Angled Arm, Held in Front, Vector Returned: ~23
Attachment 693
Right-Angled Arm, Held to Side, Vector Returned: ~16

I'm confused as to how thought this would be a simple way. Should I try to make a triangle instead? Or should I just be returning one Euler value and finding the angle from that?

 Jeff 04-09-2015 06:01 PM

You would need to track three points (hand, elbow, and shoulder) in order to get two vectors and then calculate the angle between those.

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