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Using quaternions to simulate joint articulation and deformation.

April 16, 2008

Charles

So I’ve been looking into using quats to simulate joint rotation and deformation. What I’ve found out is that most joints of a human can fall into two systems: single and double quaternion systems. If a bone system doesn’t twist using its bone like the forearm then it can fall into a single quat system, which dictates just a direction , resolution of the twist happens naturally when two perpendicular axis’ come together at 90 degrees.

If a system has a twist dictated by bones in conjunction with muscle deformation, then one quaternion is needed to dictate the twist space the second ‘deformation’ quat rides on. With this we can say that twist is not only dictated by the resolution of the system it exists in, but by the spin this system dictates. The order of which system drives each space is important.

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2 Comments

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  1. April 22, 2008

    hey charles,
    do you think the quaternions system can be used in maya without coding custom plugin.
    this phenomenon of two axis coming to each other (gimbal i suppose) is very frustrating.
    can you give any exaple of this rotation method been used in CG production

    meanwhile i checked one plugin which is giving great results with shoulder twist..
    its based on dual quaternion skinning..

    http://www.highend3d.com/maya/downloads/plugins/animation/MayaSkinClusterDq-4625.html

    thanks
    sunny

  2. joeedh #
    June 1, 2008

    http://isg.cs.tcd.ie/projects/DualQuaternions/

    Here’s a link to the original (eh I think) dual quaternion skinning paper.

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