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

BBerco bebe0705 at colorado.edu
Mon Feb 6 08:33:09 EST 2017

thank you for the detailed explanation. Here's some context information on
how this came up:

I ran into this problem while trying to reconstruct the connectivity table
between the edges (each edge being identified by a sorted pair of vertex
indices) and the polydata facets they belong to.

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).

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?


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