[vtkusers] Unexpected scalar/vector value of zero when using vtkProbeFilter

[Joy P. Ku]

I am using the vtkProbeFilter to map a mesh that is in the z=0 plane
onto a pre-defined set of points in the z=0 plane.  While this seems
to do the trick for most of the points, I occasionally get a value
of 0 for the scalar at a point where I wouldn't expect a zero.  More
specifically, a 3D plot of the magnitudes of the mesh should give
a paraboloid.  The output of the vtkProbeFilter produces the
paraboloid but with an occasional point having a magnitude of
zero.  These points seem to occur randomly, both near the peak of
the paraboloid and near the edges.

Are there limitations to the vtkProbeFilter that might produce this
phenomenon?  If so, how could I get around it?

Thanks,
Joy Ku
joyku at stanford.edu