[vtkusers] Problem with sampling using vtkProbeFilter

[Charles Boivin]

Hello all,

I have been using the vtkProbeFilter with an imagedata as a source and
some polydata surface (an isosurface, generated from vtkContourFilter)
as input. The imagedata has point data only. This works relatively
well, except at the edges of my domain. I sometimes get some values
that are arbitrarily set to zero there. I have attached an image
(isosurfaceproblem.png) that shows that problem -- I know for a fact
that the values at the bottom edge should NOT be zero (and should be
smoother than what is shown). The result is very inconsistent -- i.e.
if I change the input isosurface slightly, the location of problem
points on the bottom edge will change. I also sometimes see this
problem appear on other edges.

I have also included an image (slicenoproblem.png) that shows the same
edge, but colored on a vtkImageGeometryDataFilter (i.e. just a
'slice') of the domain. The lookup table for the value displayed is
the same for both. This shows that there is no problem for the bottom
edge...

Anyone have any idea what is going on? Is it possible that
vtkProbeFilter sometimes 'misses' the source data and therefore
outputs 0 at a location? Is there possibly a problem with my input (or
source) data? I am using VTK4.4 on a Windows machine. Source code
built using VS.Net 2003.

Thank you in advance for all ideas/suggestions...

Charles Boivin
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