Re: [Algorithms] Quaternions in IK

[Jeff L. <je...@di...>]

I looked into this for quite a while some time ago.  I asked quite a few people about it as well.  The consensus is that everyone converts from Quaternion to Euler and back to handle DOF restrictions.  Intuitively it seems that there should be a way to restrict the motion of a quaternion to a particular portion of the hypersphere.  It is a bit beyond my math skills though.  I have a math grad starting work for me this month so I can put her on the task. :) No better research tool then a graduate student.

In implementation, for me the conversion isn't too severe.  I only calculate the IK solution when needed and I classify joints that are 1 DOF so they are not effected.

-Jeff

At 05:36 AM 9/3/2000 -0700, you wrote:
>Hi all ,
>
>Does any one know an efficient way of constraining quaternions in IK without factorizing them into 3 axis quaternions ?
>Finding the required rotation quaternion in IK is pretty easy , but how can we make sure that it doesn't violate or 3 constrains of the 3DOFs of the joint ? what I'm doing now is factorizing the IK result quaternion of the joint into xrotation quaternion yrotation quaternion and zrotation quaternion , constrain them by their maximums and recombine them again , which is obviously a very expensive process.
>
>any ideas ? or maybe references ?
>
>Thanks
>
>Auday
>
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