[Insight-users] Problems with the orthogonal rotation matrix in versorRigid3DTransform

[Luis Ibanez]

Hi Patrik,

1) What version of ITK are you using ?

2) The error that you are getting indicates that the
    matrix is non-orthogonal "to a certain precision level".

3) It would seem that the file where the transform
    is saved is not using all the required precision.
   This is a common problem when writing float/double
   numbers as text.

Could you please post to the mailing list the Transform
file that is not working for loading ?

We can use it to track down the location where the
precision is being lost at the moment of writing.
Most likely what we need to fix is the "precision"
modifier of the ostream that is writing the data out.

--

If you are in a hurry, a work around would be for
you to "manually" save the array of parameters
of the transform. This will be more stable, since
it is saved as:

   Three Versor components for the rotation and
   Three Vector components for  the translation,
   and, don't forget to save also the Fixed parameters
   that will consist of the three components of the
   center of rotation.



    Thanks


         Luis


------------------------------------------------------------------------------
On Fri, Nov 27, 2009 at 9:01 AM, Patrik Brynolfsson
<patrik.brynolfsson at radfys.umu.se> wrote:
> Hello,
> I'm performing 3D rigid registration using the versorRigid3DTransform on a
> lot of images and save the resulting versors, rotation matrices, center of
> rotation and translations vectors in a text file connected to each image. My
> problem is that when I read the rotation matrix from file to perform the
> actual transform ITK complains, saying:
> "itk::ERROR: VersorRigid3DTransform(031BFC78): Attempting to set a
> non-orthogonal rotation matrix"
> It is the same matrix that ITK returned when the original registration was
> performed. How do I solve this?
> Thanks in advance,
> --
> Patrik Brynolfsson
>
>
>
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