[vtkusers] Bug? vtkNormalFilter changes # of points in polydata

Cory Quammen cory.quammen at kitware.com
Mon Feb 6 09:40:03 EST 2017

> More specifically, I need two of those: the "forward connectivity table"
> linking facets to the 3 edges they own, and the "backward connectivity
> table" linking edges to the facets they belong too. I was constructing those
> two by looping over the polydata cells, casting those cells to vtkTriangle
> so as to use
> vtkSmartPointer<vtkCell> edge = trig -> GetEdge(i);
> vtkSmartPointer<vtkIdList> pointIdList = edge -> GetPointIds();
> on the triangles. This reconstruction process fails for the backward
> connectivity table because of the spurious points/edges introduced by the
> splitting algorithm (they appear to be owned by a single facet).

Well, they are spurious in the sense that they are getting in the way
of what you are trying to do, but they do serve a purpose.

> Do you know a more elegant procedure to get access to all the "real" edges
> (in the form of the indices of the vertices forming each edge) present in
> the polydata before the splitting?

The easiest solution is to turn off splitting. The second easiest
solution is to do your processing on the data input to the
vtkPolyDataNormals filter and apply the vtkPolyDataNormals only as a
last step prior to display. Are either of these options?


> Best,
> Ben
> --
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> Sent from the VTK - Users mailing list archive at Nabble.com.
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Cory Quammen
Staff R&D Engineer
Kitware, Inc.

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