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Motion capture & root rotation


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I am using a kinect2 for data capture inside of Blender.  For all but the root bone, I am using the absolute joint position method.  Trying to use the rotation quaternions is a nightmare, which is not helped by:

  • Blender being right-handed & Kinect2 being left
  • Y & Z dimensions switched
  • Data capturing & not mirroring
  • quaternion method is all or nothing.  Complete garbage where you cannot figure out what is wrong.  With location data you can sort of see what you are doing wrong.

I get decent results, when facing forward, but if I do a twirl location data can never work.  I was think of using the quaternion data solely for the rootbone.  Unfortunately, the data looks kind of weird.  Below, is a clockwise twirl.  I have not corrected for being a mirror yet.  The second group is using Blender's quaternion.to_euler('XYZ').  Can anyone explain this data?  Do people even try to data capture stuff like this?


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Doing some more searching, I found some info on using the location data for getting orientation to camera as well.  I had tried to do this myself as well, but using the hips instead of shoulders.  Mine was a real kludge.  The last response was:


That's actually pretty easy:

Xvector =  (Right Shoulder Position) - (Left Shoulder Position)

Yvector = (Head Position) - (SpineBase Position)

Zvector = CrossProduct(Xvector,Yvector)


Zvector will give you the overall pointing direction of the body relative to the camera

Vicente Penades

Not sure exactly how to do this yet, but I know for a fact that the location data is consistent all the time.  Any comments?

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I had serious issues capturing into Blender. I ran my Kinect(s) into MotionBuilder and then exported FBX to Blender without any problems. In working with motion capture for 20+ years, I see too many problems with capturing into Blender right now; until someone writes a proper plugin which is simple to use.


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