[vtkusers] vtkExtractEdges changes point IDs?

[David Gobbi]

On Fri, Apr 9, 2010 at 11:37 AM, David Doria <daviddoria+vtk at gmail.com> wrote:
> I made a 5x5 plane source. (Throughout this discussion, I am using
> paraview selection spreadsheet view to get these IDs). The ID of the
> center point is 12. The ID of the point to the left of it is 11. When
> I run it through vtkExtractEdges, the ID of the center point is still
> 12, but the point to the left of the center point changes to 10, and
> other points have changed as well. Is this expected? Or a bug?

VTK filters are not guaranteed to output the same IDs for points as
their inputs.  In particular, any filters that extract just part of
the input geometry will usually throw away any points that aren't part
of the output geometry.

Also, most filters will merge points that are coincident, i.e. if two
inputs points are at exactly the same position in the input then they
will often be merged in the output.

   David