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

[Patrik Brynolfsson]

Hello!

I'm using version ITK 3.16.

The code for writing to file is very simple and the relevant code is
attached below:

/* Get relevant parameters*/
TransformType::MatrixType matrix    = transform->GetRotationMatrix();
TransformType::OffsetType offset    = transform->GetOffset();
TransformType::MatrixType invMatrix = matrix.GetInverse();
TransformType::ParametersType finalParameters = transform->GetParameters();

/* Write to file */
std::ofstream trans(fileName,std::ios::app);
trans << "Image: " << imageNumber << std::endl;
trans << "\tMatrix:" << std::endl;
trans << "\t\t" << matrix[0][0] <<" "<< matrix[0][1] <<" "<< matrix [0][2]
<< std::endl;
trans << "\t\t" << matrix[1][0] <<" "<< matrix[1][1] <<" "<< matrix [1][2]
<< std::endl;
trans << "\t\t" << matrix[2][0] <<" "<< matrix[2][1] <<" "<< matrix [2][2]
<< std::endl << std::endl;
trans << "\tInverse matrix:" << std::endl;
trans << "\t\t" << invMatrix[0][0] <<" "<< invMatrix[0][1] <<" "<< invMatrix
[0][2] << std::endl;
trans << "\t\t" << invMatrix[1][0] <<" "<< invMatrix[1][1] <<" "<< invMatrix
[1][2] << std::endl;
trans << "\t\t" << invMatrix[2][0] <<" "<< invMatrix[2][1] <<" "<< invMatrix
[2][2] << std::endl << std::endl;
trans << "\tOffset vector:" << std::endl;
trans << "\t\t" << offset[0]<<" "<<offset[1]<<" "<<offset[2]<< std::endl <<
std::endl;
trans << "\tVersor transform:" << std::endl;
trans << "\t\t" << finalParameters[0]<<" "<<finalParameters[1]<<"
"<<finalParameters[2]<<" "<< finalParameters[3] <<" "<<finalParameters[4]
<<" "<<finalParameters[5] <<std::endl << std::endl;
trans << "\tCenter of Rotation:" << std::endl;
trans << "\t\t" << transform->GetCenter()[0] <<" " <<
transform->GetCenter()[1] <<" "<< transform->GetCenter()[2]<< std::endl <<
std::endl;

A result file might look like:

Image: 1
Matrix:
0.99998 -0.00105588 -0.00631213
0.00111111 0.999961 0.00875183
0.00630265 -0.00875866 0.999942

Inverse matrix:
0.99998 0.00111111 0.00630265
-0.00105588 0.999961 -0.00875866
-0.00631213 0.00875183 0.999942

Offset vector:
0.453916 -0.946682 0.388294

Versor transform:
-0.00437769 -0.00315374 0.000541755 0.259976 -0.727504 0.0970571

Center of Rotation:
-1.96057 31.6714 25.4334

I hope this helps to fix the problem!


Regards

Patrik

2009/11/30 Luis Ibanez <luis.ibanez at kitware.com>

> 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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-- 
Patrik Brynolfsson
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