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

Sun Dec 13 06:55:10 EST 2009

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
>>
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>
>