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

[BBerco]

Cory, 
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?

Best,
Ben




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