[vtkusers] confused with vtkProbeFilter

[Martin Genet]

Thanks for your help, Sujin.

What do you mean exactly by "your code works for me"? I sat the arrays 
names but am still getting the same behavior: the code runs fine, but I 
can't find the interpolated data. Do you know where it is? Thanks again.

Martin

On 13/05/2016 18:53, Sujin Philip wrote:
> Hi Martin,
>
> You need to set names for the point and cell data arrays.
> farray.SetName("pointdata") and farray.SetName("celldata")
>
> after doing that your code works for me.
>
> -Sujin
>
>
> On Fri, May 13, 2016 at 12:16 PM, Martin Genet 
> <martin.genet at polytechnique.edu 
> <mailto:martin.genet at polytechnique.edu>> wrote:
>
>     Dear everyone:
>
>     Sorry for the triviality, but I'm getting confused with
>     vtkProbeFilter: trying to probe an image with a mesh (not the
>     opposite: I need the mesh data interpolated onto the image
>     points), but can't get it to work.
>
>     Consider the following code:
>
>         import numpy
>         import vtk
>
>         image = vtk.vtkImageData()
>         image.SetDimensions([3, 3, 1])
>         image.SetSpacing(1./numpy.array(image.GetDimensions()))
>         image.SetOrigin(numpy.array(image.GetSpacing())/2)
>
>         points = vtk.vtkPoints()
>         points.InsertNextPoint([1./4, 1./4, 2./4])
>         points.InsertNextPoint([3./4, 1./4, 2./4])
>         points.InsertNextPoint([3./4, 3./4, 2./4])
>         points.InsertNextPoint([1./4, 3./4, 2./4])
>
>         cell = vtk.vtkQuad()
>         cell.GetPointIds().SetId(0, 0)
>         cell.GetPointIds().SetId(1, 1)
>         cell.GetPointIds().SetId(2, 2)
>         cell.GetPointIds().SetId(3, 3)
>
>         cell_array = vtk.vtkCellArray()
>         cell_array.InsertNextCell(cell)
>
>         ugrid = vtk.vtkUnstructuredGrid()
>         ugrid.SetPoints(points)
>         ugrid.SetCells(vtk.VTK_QUAD, cell_array)
>
>         farray = vtk.vtkFloatArray()
>         farray.SetNumberOfComponents(1)
>         farray.SetNumberOfTuples(1)
>         farray.SetTuple1(0, 2.)
>         ugrid.GetCellData().AddArray(farray)
>
>         farray = vtk.vtkFloatArray()
>         farray.SetNumberOfComponents(1)
>         farray.SetNumberOfTuples(4)
>         farray.SetTuple1(0, 2.)
>         farray.SetTuple1(2, 2.)
>         farray.SetTuple1(3, 2.)
>         farray.SetTuple1(4, 2.)
>         ugrid.GetPointData().AddArray(farray)
>
>         probe = vtk.vtkProbeFilter()
>         if (vtk.vtkVersion.GetVTKMajorVersion() >= 6):
>             probe.SetInputData(image)
>             probe.SetSourceData(ugrid)
>         else:
>             probe.SetInput(image)
>             probe.SetSource(ugrid)
>         probe.Update()
>         probed_image = probe.GetOutput()
>
>
>     Problem is: probed_image contains only one array, called
>     vtkValidPointMask, but no interpolated data.
>
>     If I do:
>
>         probed_scalars =
>         probed_image.GetPointData().GetArray("vtkValidPointMask")
>         for k_voxels in xrange(probed_scalars.GetNumberOfTuples()):
>         print probed_scalars.GetTuple1(k_voxels)
>
>     I'm getting:
>
>         0.0
>         0.0
>         0.0
>         0.0
>         1.0
>         0.0
>         0.0
>         0.0
>         0.0
>
>     So I'm guessing the filter is able to figure out which image point
>     lies within the mesh and which does not, but I can't find the
>     interpolated data? Any help would be super appreciated. Thanks!
>
>     Martin
>
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