[Insight-users] quaternion registration initialization

[Luis Ibanez]

Hi Michiel,


You may want to do the following:

1) Use the class

        itkVersorRidig3DTransformInitializer

    that you will find in:

Insight/Code/Common/
      itkCenteredVersorTransformInitializer.h
      itkCenteredVersorTransformInitializer.txx


   To find the Versor that overlaps the centers of
   of the images and aligns their axis of moments.


2) Use the values from the resulting Versor
    to initialize the quaternion.

    * Set the same center of rotation
    * Set the same translation
    * Set the first three quaternion components
       to the value of the three Versor components
       and compute the fourth component as

        c = sqrt( 1.0 - a^2 + b^2 + c^2 )

3) Or ... even better, simply use the

           itkVersorRigid3DTransform

    instead of the Quaternion Transform.


4) For more details about the relation
    between Quaternions and Versors,
    please look at the Tutorials:

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




 Regards


      Luis



-------------------------------------------------------------------
On Thu, Mar 11, 2010 at 12:07 PM, michiel mentink
<michael.mentink at st-hughs.ox.ac.uk> wrote:
>
> Has anybody got an idea how to initialize Quaternion Registration and its'
> optimizer?
>
> When I run the registration, there's no optimization:
>
> 0   -0.217825   [0, 0, 0, 1, 2.34375, 53.125, 2.64351]
> 1   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 2   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 3   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 4   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 5   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 6   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 7   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 8   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 9   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
> 10   0   [0.141868, -0.434396, 0.649002, -0.608251, 12.9582, 50.573,
> 4.15614e+265]
>
>
> I suspect it has something to do with  optimizer->SetMetric() but I can't
> figure out what
> to put there.
>
> cheers,
>
> Michael
>
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