[Insight-users] Convert vector field from vtkUnstructuredGrid to itk::Image with interpolation

Sun Dec 13 07:09:31 EST 2009

Hi Dirk,

Thanks for letting us know.

You are right,

I missed to mention the itk::DeformationFieldSource class
and its examples of use in:

     Insight/Examples/Registration/
                      DeformationFieldInitialization.cxx

     Insight/Examples/Registration/
                      LandmarkWarping2.cxx

Thanks for sharing the solution that you found.

        Luis

----------------------------------------------------------------------------
On Sun, Dec 13, 2009 at 6:55 AM, Dirk Boye <body at nabla.org> wrote:
> Hi Luiz,
>
> Thank you very much! I used itk::DeformationFieldSource
> That did it quite well!
>
> Cheers,
> Dirk
>
>> Hi Dirk,
>>
>> Two options:
>>
>>      A) Use any of the KernelTranforms
>> http://www.itk.org/Doxygen/html/classitk_1_1KernelTransform.html
>>          for example the
>> http://www.itk.org/Doxygen/html/classitk_1_1ThinPlateSplineKernelTransform.html
>>
>>
>> or
>>
>>     B) Use the itkBSplineScatteredDataPointSetToImageFilter.h
>>
>>
>> ---
>>
>> If you go for (A), you can set the Source Landmarks to the
>> positions of the tails of the vectors, and put the Target landmarks
>> to the positions of the heads of the vectors.
>>
>> Then you can simply use the TransformPoint() method, to
>> evaluate the value of the Vector at every new point in space.
>> Note that the transform will give you the position of the head
>> of the vector, therefore, to get the actual vector you need to
>> do:
>>
>>     VectorType v =  transform->TransformPoint( p )  -  p;
>>
>> ---
>>
>> If you go for (B), please read the following paper in the
>> Insight Journal:
>>
>> N-D C^k B-Spline Scattered Data Approximation
>> Tustison N.J., Gee J.C.
>> PICSL, University of Pennsylvania
>>
>> http://hdl.handle.net/1926/140
>> http://www.insight-journal.org/browse/publication/57
>>
>>
>>
>> Regards,
>>
>>
>>        Luis
>>
>>
>>
>> ------------------------------------------------------------
>> On Thu, Dec 10, 2009 at 5:47 AM, Dirk Boye <body at nabla.org> wrote:
>>> Dear list,
>>>
>>> Let's say I have a list of vectors in an vtkUnstructuredGrid like
>>> this:
>>>
>>> # vtk DataFile Version 3.0
>>> vtk output
>>> ASCII
>>> DATASET UNSTRUCTURED_GRID
>>> POINTS 5 float
>>> -2 2 0 2 2 0 0 0 0
>>> -2 -2 0 2 -2 0
>>> CELL_TYPES 0
>>>
>>> POINT_DATA 5
>>> VECTORS vectors float
>>> 1 -1 0 1 1 0 1 0 0
>>> 1 1 0 1 -1 0
>>>
>>>
>>> I'd like to create a continuous vector field 'image' of dimensions
>>> 4x4x1 with a spacing of 1.
>>>
>>> How can I read the vectors into a itk::Image and do an interpolation
>>> (BSpline for example) on the vectors?
>>> Usually one resamples an image and interpolates the new pixels... but
>>> with only some vectors given like above and given image dims/spacing
>>> I have no clue.
>>>
>>> Attached image is a sketch of what I'd like to do :)
>>>
>>> Are there any nice classes to do that?
>>>
>>> Thanks,
>>> Dirk
>>>
>>> _____________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at
>>> http://www.kitware.com/opensource/opensource.html
>>>
>>> Kitware offers ITK Training Courses, for more information visit:
>>> http://www.kitware.com/products/protraining.html
>>>
>>> Please keep messages on-topic and check the ITK FAQ at:
>>> http://www.itk.org/Wiki/ITK_FAQ
>>>
>>> Follow this link to subscribe/unsubscribe:
>>> http://www.itk.org/mailman/listinfo/insight-users
>>>
>>>
>>
>>
>
>