[Insight-users] regid transformation matrix

[Luis Ibanez]

Hi Henry,

Keep in mind that the definition of orthogonality is:

                    M * M^T  =   Identity

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


(as Ruben pointed out that doesn't implies that the matrix
  is antisymmetric)


You have to be a very good mathematician to judge the orthogonality
of a Matrix by just looking at it  :-)


I would suggest that instead, you use the Orthogonality test that is
available in the itkRigid3DTransform.h:


    if( !rigid3DTransform->MatrixIsOrthogonal( matrix, tolerance ) )


The test takes your matrix, multiplies it by its transpose and then
compare the result against an identity matrix using the Tolerance
that you provide as second argument.



    Regards,


       Luis



------------
Henry wrote:
> Hi I am using "LandmarkInitializedMutualInformationRegistration" from
> InsightApplications-3.4.0 and I have one question about the
> transformation matrix from registration results: although I choose
> rigid transformation, the transformation matrix are not seemed to be
> orthogonal, for example:
> 0.999982 0.00137216 -0.00581659
> -0.00133902 0.999983 0.0056975
> 0.00582431 -0.00568961 0.999967
> 
> I guess it is because affine transformation is used even for rigid
> registration? How to use rigid transformation instead?
> 
> Thanks!
> Henry
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