[Insight-users] Simple question : Versor == Unit Quaternion; axis and angle

[Luis Ibanez]

Hi Yu,

Please read the Registration chapter of the ITK Software Guide


       http://www.itk.org/ItkSoftwareGuide.pdf


The Versor transform is described there in detail.

A Versor is the correct name for a unit quaternion,
as it was defined by Hamilton in 1886.

It can be associated to an axis of rotation and an angle.

the variable "axis" is the axis of rotation, and it is
defining that the Versor is describing a rotation around
the Z axis.

You should also read the two tutorials on Quaternions:

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


  Regards,


      Luis




--------------------------------
Yu Qi wrote:

> This code is from the ITKGuide,Rigid Transform in 3D
>  
> *******************************************************
> typedef TransformType::VersorType VersorType;
> typedef VersorType::VectorType VectorType;
> VersorType rotation;
> VectorType axis;
> axis[0] = 0.0;
> axis[1] = 0.0;
> axis[2] = 1.0;
> const double angle = 0;
> rotation.Set( axis, angle );
> transform->SetRotation( rotation );
> *******************************************************
> I want to know what  the variable  axis,angle are.
> And why give them those values?
>  
>  
>  
> 
> 
> *Best Regards!*
> ** 
> *Yu Qi*
>  
>  
>