[Insight-users] Quaternion does not equal Versor

[Groch, Anja]

Hi,

I'm not so familiar with the difference of a versor and a quaternion, but I thought, the 4 representing values should be the same in both structures.

If so, then there might be a bug, when converting a itkVersorRigid3DTransform into a vnl_quaternion (or I'm just doing the conversion in a wrong way).

I'm doing the conversion of a itk::VersorRigid3DTransform<double>::Pointer transform as follows:

vnl_quaternion<double>(transform->GetMatrix().GetVnlMatrix());

The resulting quaternion does not equal the versor, for example read out with ->GetVersor(). From the few examples I tried, it looks as if only the direction of the rotation changes, but rotation axis and angle are the same.

Thanks a lot in advance for your help!
Best
Anja

--------------
Dipl.-Inform. Anja Groch
German Cancer Research Center (DKFZ)
Div. Medical and Biological Informatics
Junior Group: Computer-assisted Interventions (E131)
Im Neuenheimer Feld 280
69120 Heidelberg, Germany

Email:  a.groch at dkfz.de<mailto:a.groch at dkfz.de>
Phone:  (+49) 6221/42-3548
Fax:    (+49) 6221/42-2345
http://www.dkfz-heidelberg.de/de/mbi/people/Anja_Groch.html


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