Re: [Algorithms] Quaternions in IK

[Jason Z. <zi...@n-...>]

Can you convert between Quaternion and Euler without any loss of
information?  I have a routine to convert Euler->Quat but I've never seen
one that goes from Quat->Euler.  This would be most helpful for my current
project.

- Jason Zisk
- nFusion Interactive LLC


----- Original Message -----
From: "Jeff Lander" <je...@di...>
To: <gda...@li...>
Sent: Tuesday, September 05, 2000 8:06 PM
Subject: Re: [Algorithms] Quaternions in IK


> 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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