[Insight-users] VersorTransform takes 6 parameters?

[Luis Ibanez]

Hi Michael,

My apologies, I missed the point in the previous email.

The VersorTransform I actually implementing pure rotations
in 3D space (no translation at all). This transform is
using 3 parameters only. The parameters are the three
components of the Versor. The bug was in the Doxygen
documentation which was wrongly making mention of 6
parameters and an offset. There are only 3 parameters
in this transform.

The VersorRigid3DTransform on the other hand is applying
a rigid 3D transform using a Versor for representing
rotation and a Vector for representing translations.

Something we will unify in the short future is that
the VersorRigid3DTransform has an option for setting
the Center of rotation while the VersorTransform uses
the default image origin of coordinates. Due to that
the VersorRigid3DTransform end up having 9 effective
parameters.

This will probably change, so both transforms allow
users to set the rotation center, and none of them
uses the center of rotation coordinates as part of
its parameters.



  Hope this is less obscure now,


    Thanks


     Luis


BTW: The doxygen documentation for the itkVesorTransform
has been fixed. It will not show up in the web until
tomorrow though.


---------------------
Michael Kuhn wrote:
> Hi Luis,
> 
> I am a bit confused as far as the distinction of the different 
> transforms is concerned. I thought a versor is the rotational part of a 
> quaternion and a VersorTransform only does a rotation. Isn't there the 
> VersorRigid3DTransform to "add" a translation to the VersorTransform? Or 
> what's the difference between a VersorTransform and a 
> VersorRigid3DTransform?
> 
> Thanks,
> 
> Michael
> 
> 
> 
> Luis Ibanez wrote:
> 
>>
>> Hi Michael,
>>
>>
>> The VersorTransform class represents
>> a Rigid Transform in 3D.
>>
>> The rotational part is represented by
>> a Versor (a unit quaternion) while the
>> translational part is represented by a
>> Vector.
>>
>> The Six parameters are:
>>
>> 1) the first 3 are the components
>>    of the Versor representing the rotation
>>
>> 2) the last 3 are the components
>>    of the Vector representing the translation.
>>
>>
>> ---
>>
>> We have to update this on the SoftwareGuide,
>>
>> Thanks for pointing this out,
>>
>>
>> Regards,
>>
>>
>>    Luis
>>
>>
>>
>>
>> ------------------------
>> Michael Kuhn wrote:
>>
>>> Hi,
>>>
>>> in the doxygen documentation of the SetParameters() method of the 
>>> versor transform is written, that the versor transform takes 6 
>>> parameters. Obviously, the last 3 parameters represent an offset. 
>>> Unfortunately I only found the explanation of the first 3 parameters 
>>> in the itk users guide. Can anyone explain me, what this offset means?
>>>
>>> Thanks,
>>>
>>> Michael
>>>
>>> _______________________________________________
>>> Insight-users mailing list
>>> Insight-users at itk . org
>>> http://www . itk . org/mailman/listinfo/insight-users
>>>
>>
>>
>>
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>>
> 
> 
>