[Insight-users] registration results

Fri Mar 23 16:31:17 EST 2007

Hi Tony,

In the PointSetToImageRegistration, the PointSet is the collections of
points that are mapped into the MovingImage.

The Transform that results from the registration process is the *SAME*
that you want to use in order to resample the Point and overlap them
with the image.

What you may find conterintuitive, if you are comparing this with the
image to image registration, is that in the image-to-image case, the
Moving image is that one that is resampled.

In your case, what you need to do is to simply take the transform that
is the result of your registration process and use it as input to the
TransformMeshFilter. This filter will map your point set into the
coordinate system of the moving image.

    Regards,

       Luis

------------------
tony hakki wrote:
> Dear Luis; first of all I would like to thank your quick reply, I just 
> want to verify something, you know I have tried to implement poinst set 
> to image registration. I would like to use final registration parameters 
> to the my point set,which was selected  Fixedpoint set at the beginning 
> of the registration.  So, Instead of  to apply final registration 
> results to my moving image I  would like to apply the  "*OPPOSITE*" 
> final registration parameters  to my point set I can save time and it 
> can be implemented quickler.  Am I right ?
> Thank you
> Tony
> 
> ----- Original Message ----
> From: Luis Ibanez <luis.ibanez at kitware.com>
> To: tony hakki <tony2007vtk at yahoo.com>
> Cc: insight-users at itk.org
> Sent: Friday, March 23, 2007 8:05:38 PM
> Subject: Re: [Insight-users] registration results
> 
> Hi Tony,
> 
> The components of a Versor *ARE NOT* angles.
> 
> A versor *IS NOT* a triplet of Euler angles.
> 
> 
> Instead, it is equivalent to a Unit Quaternion.
> 
> 
> Please refer to the ITK Software Guide for
> a description of the concept of Versors.
> 
>    http://www.itk.org/ItkSoftwareGuide.pdf
> 
> 
> If you have a rotation of T degrees around
> an axis defined by a unit vertor x,y,z,
> 
> Then the components of the Versor will be
> equal to:
> 
> 
>         Vx = x * sin( T / 2 )
>         Vy = y * sin( T / 2 )
>         Vz = z * sin( T / 2 )
> 
> 
> You may find useful to read also the Tutorials
> on Quaternions:
> 
> 
> http://www.itk.org/CourseWare/Training/QuaternionsI.pdf
> http://www.itk.org/CourseWare/Training/QuaternionsII.pdf
> 
> 
> The reason why your image "seems" to translate is probably
> that you have not set correctly the center of rotation
> of the transformation.  A rotation performed around a
> center that is far from the field of view of the image,
> will 'look' like a translation.
> 
> You will find this effect explained in detail in the
> ITK Software Guide:
> 
>       http://www.itk.org/ItkSoftwareGuide.pdf
> 
> 
> in section "6.9.4" "Resample Image Filter",
> in pdf-pages 254-275.
> 
> Pay particular attention to figuires:
> 
>            6.51 and 6.52
> 
> 
> 
>     Regards,
> 
> 
>        Luis
> 
> 
> -----------------
> tony hakki wrote:
>  > hello all;
>  > I have tried to implement point set to image registration;I would like
>  > to manipulate the results like that:
>  > Supposing that these are the registation results;
>  >
>  > const double versorX = finalParameters[0];
>  >
>  > const double versorY = finalParameters[1];
>  >
>  > const double versorZ = finalParameters[2];
>  >
>  > const double finalTranslationX = finalParameters[3];
>  >
>  > const double finalTranslationY = finalParameters[4];
>  >
>  > const double finalTranslationZ = finalParameters[5];
>  >
>  >  
>  >
>  >  
>  >
>  > I would like to manipulate them like that:
>  >
>  >  
>  >
>  > finalParameters[0]=2*vtkMath::Pi()-versorX;
>  >
>  > finalParameters[1]=2*vtkMath::Pi()-versorY;
>  >
>  > finalParameters[2]= 2*vtkMath::Pi()-versorZ;
>  >
>  > *finalParameters[3]=finalTranslationX *(-1);*
>  >
>  > *finalParameters[4]=finalTranslationY *(-1);*
>  >
>  > *finalParameters[5]=finalTranslationZ *(-1);*
>  >
>  > **
>  >
>  > **
>  >
>  > *When I manipulate *finalParameters[0],
>  > finalParameters[1],finalParameters[2]  , It doesn't give any error,  but
>  > these parameters are for rotation parameters  where as my image
>  > translate when I change these parameters.*Why it doesn't rotate but
>  > translates through the x,y,z coordinate system When I manupulate them.*
>  >
>  > On the other hand I couldn't manupulate the rest of the parameters
>  > finalParameters[3],,finalParameters[4],,finalParameters[5], ,it gives
>  > break or continue error when I run my program. And these are the
>  > translation parameters,aren't they? *Why I couldn't manupulate these
>  > parameters as I showed above? *
>  >
>  >  
>  >
>  > here is the my translation code:
>  >
>  > typedef itk::TranslationTransform<float,3> NTransformType;
>  >
>  > NTransformType::Pointer finalTransform = NTransformType::New();
>  >
>  > finalTransform->SetParameters( finalParameters );  //this is
>  > registration result
>  >
>  > typedef FMeshType::PointsContainer PointsContainerType;
>  >
>  > typedef FMeshType::PointsContainerPointer
>  >
>  > PointsContainerPointer;
>  >
>  > typedef itk::TransformMeshFilter<
>  >
>  > FMeshType,
>  >
>  > FMeshType,
>  >
>  > NTransformType > FilterType;
>  >
>  >  
>  >
>  > // Create a Filter
>  >
>  > FilterType::Pointer filter = FilterType::New();
>  >
>  > // Connect the inputs
>  >
>  > filter->SetInput( input_mesh );
>  >
>  > filter->SetTransform( finalTransform );
>  >
>  > // Execute the filter
>  >
>  > filter->Update();
>  >
>  > std::cout << "Filter: " << filter;
>  >
>  > // Get the Smart Pointer to the Filter Output
>  >
>  > FMeshType::Pointer outputMesh = filter->GetOutput();
>  >
>  > std::cout << "Output Mesh has " << outputMesh->GetNumberOfPoints();
>  >
>  > std::cout << " points " << std::endl;
>  >
>  > // Get the the point container
>  >
>  > FMeshType::PointsContainerPointer
>  >
>  > transformedPoints = outputMesh->GetPoints();
>  >
>  >
>  > _______________________________________________
>  > Insight-users mailing list
>  > Insight-users at itk.org
>  > http://www.itk.org/mailman/listinfo/insight-users
> 
> 
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