[vtkusers] vtkExtractEdges changes point IDs?

[David Gobbi]

On Fri, Apr 9, 2010 at 11:54 AM, David Doria <daviddoria+vtk at gmail.com> wrote:
>
> In this case, there are no coincident points and all input points are
> passed to the output. Apparently they are still not guaranteed to have
> the same ID. Is this accurate?

Yes.  Here is what happens.  The "for" loops in the filter traverse
the geometry, i.e. the cells.  Whenever an input point is needed for
the output geometry, it is inserted into the output points.  As a
result, the sorting of the output points is different from the input
points.

Conversely, for filters that traverse the points (as opposed to
traversing the cells), the output points are usually kept in the same
order as the input points.

   David