[vtkusers] Bug in vtkPolyDataNormals?

[danimede]

Hi All,

I have found a weird computation in vtkPolyDataNormals.cpp. The issue is in
the follow piece of code:

for (i=0; i < numNewPts; i++) {
      newNormals->GetTuple(i, vertNormal);
      length = vtkMath::Norm(vertNormal);
      if (length != 0.0) {
          for (j=0; j < 3; j++) {
              n[j] = vertNormal[j] / length * flipDirection;
          }
      }
      newNormals->SetTuple(i,n);
}

In the code if we have a length equal to zero we set in the i-th tuple the
normal values of the (i-th)-1 point!
Is it a bug or maybe there are some hypothesis like consecutive index points
can have the same normal vector? 
Probably the solution is to set the normal to {0.0 , 0.0 , 0.0} if we have a
length equal to zero.

Regards,
Daniele



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