Skinning a Skeleton: Deriving JMi of Skinning Equation

the following is snippets of code from the DAE (it is actually a finger):

<node id=“node-Bone01” name=“Bone01” sid=“joint0” type=“JOINT”>
<translate>5.89163 -79.8736 -3.48687e-006</translate>
<rotate>-0.258444 0.683084 -0.683084 -208.981</rotate>
<scale>-1 -1 -1</scale>
<node id=“node-Bone02” name=“Bone02” sid=“joint1” type=“JOINT”>
<translate>23.7247 6.86565e-007 7.62939e-006</translate>
<rotate>0.0163536 0.998265 -0.0565595 -33.6487</rotate>
<node id=“node-Bone03” name=“Bone03” sid=“joint2” type=“JOINT”>
<matrix>0.99652 -0.07105 0.0436054 53.9616 0.04415 0.00611277 -0.999006 -4.76837e-007 0.0707129 0.997454 0.00922835 7.62939e-006 0 0 0 1</matrix>
<node id=“node-Bone04” name=“Bone04” sid=“joint3” type=“JOINT”>
<matrix>0.993619 -0.00243863 0.112762 36.7931 0.112774 0.00598921 -0.993602 0 0.00174767 0.999979 0.006226 -7.62939e-006 0 0 0 1</matrix>
<node id=“node-Bone05” name=“Bone05” sid=“joint4” type=“JOINT”>
<matrix>0.99796 -0.0221926 0.0598742 18.3381 0.059888 -4.02778e-005 -0.998205 0 0.0221551 0.999754 0.00128886 7.62939e-006 0 0 0 1</matrix>
<node id=“node-Bone06” name=“Bone06” sid=“joint5” type=“JOINT”>
<matrix>0.999569 -0.0293479 1.49012e-008 19.4873 0 0 -1 -9.53674e-007 0.029348 0.999569 -3.72529e-009 7.62939e-006 0 0 0 1</matrix>
</node>
</node>
</node>
</node>
</node>
</node>

May I know how do i derive the JMi of “Joint 5”?

  • So I will just use the translate,rotate and scale info and create a 4x4 matrix?
  • How come the first 3 numbers in the <rotate> tag is not 0 or 1 but rather strings of dec numbers?
  • Then how do I handle the <matrix> tag?

Actually i am quite lost in skinning a skeleton, is there a tutorial somewhere with step by step guide? Or anything that can point me in the right direction?

[I am actually trying to recreate a 3D Model (created and rigged in 3D Studio Max) in OpenGL so that i can control it with input from a VR glove]

May be you can read the following tutorial written by me.

http://www.wazim.com/Collada_Tutorial_1.htm


waZim