[Insight-users] how can we calculate the rotation from versor

[Luis Ibanez]

Hi Alireza,


A Versor *IS* a rotation.

A versor is represented using the three first components
of a Quaternion.

Please read the tutorial on Quaternions:

     http://www.itk.org/CourseWare/Training/QuaternionsI.pdf
     http://www.itk.org/CourseWare/Training/QuaternionsII.pdf

and the description of Versors in the Wikipedia:

       http://en.wikipedia.org/wiki/Versor

The four components of a Quaternion correspond to:


       q0 = Ax * sin( T / 2 )
       q1 = Ay * sin( T / 2 )
       q2 = Az * sin( T / 2 )
       q3 =      cos( T / 2 )


where (Ax,Ay,Az) are the components of the axis
of rotation and T is the angle of rotation.

Versors are composed of only the components

          q0,q1,q2





    Regards,


        Luis


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Alireza Salamy wrote:
> Hi all users,
> I would like to know how can we calculate the rotation from versor?Are 
> the three first parameter in the solution of Itarative closestpoint2,versor?
> the second question is related to 2D/3D point set registration.Can any 
> body tell me in which part of the code of Itarativeclosestpoint2 shall I 
> make some changes to convert it from 3D/3D pointset registration to 
> 2D/3D pointset registration?
> thanks alot,
> Alireza
> 
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