[vtkusers] Applying transform to volume

[P B]

Hi,    I've been using vtkThinPlateSplineTransform and have been successful to get a result applied to landmarks, but have a question for transforming a volume. 
 
First, is there a way to force connectivity between points in a volume? More specifically this is what I have done and where is my problem: - I created a thin plate spline transform with source points (from an MR volume) and target points (from a CT volume).- To apply the transformation to the points, I used vtkTransformPolyDataFilter and specified a vtkPolyData structure with positions (vtkPoints) and connectivity (using vtkCellArray).- The resulting displacement for the source points is valid and they are now moved to the target points. I want to apply this exact transformation to a volume that contains only intensities. I can use vtkImageReslice and specify the transform from vtkThinPlateSplineTransform but the volume intensities do not seem to move exactly as the landmarks do and I wonder if the problem might not be the connectivity that is not respected in the final displacement. I cannot use vtkTransformPolyDataFilter with a volume image. Does anyone have an idea what I could do to specify a connectivity constraint? 
 
I have another question regarding inverse. In some examples (but not all) on the web, I see that the transform is inversed before using reslice. In what situation does the inverse need to be used?
Thanks in advance for you help!Pascale
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