Method operator()

Common/DataModel/vtkPolygon.cxx:134–171

   */
  template <class ArrayT>
  void operator()(ArrayT* p, int numPts, const vtkIdType* pts, double* n)
  {
    auto points = vtk::DataArrayTupleRange<3>(p);
    using PointType = typename decltype(points)::ConstTupleReferenceType;
    double v1[3], v2[3];
    vtkIdType pointId;
    vtkIdType commonPointId = -1;
    for (pointId = 0; pointId < (numPts - 2); ++pointId)
    {
      PointType p0 = points[::GetPointId<PointIdRedirection>(pts, pointId)];
      vtkMath::Subtract(points[::GetPointId<PointIdRedirection>(pts, pointId + 1)], p0, v1);
      if (vtkMath::SquaredNorm(v1) > 0)
      {
        commonPointId = pointId;
        pointId += 2; // consume the two points we just used to obtain a non-zero v1
        break;
      }
    }

    if (pointId >= numPts || commonPointId < 0)
    {
      // Either all the points in the loop were coincident or we used
      // all the points to obtain v1 and have nothing left for v2.
      n[0] = 0;
      n[1] = 0;
      n[2] = 0;
      return;
    }

    PointType p0 = points[::GetPointId<PointIdRedirection>(pts, commonPointId)];
    for (; pointId < numPts; ++pointId)
    {
      vtkMath::Subtract(points[::GetPointId<PointIdRedirection>(pts, pointId)], p0, v2);
      vtkMath::Cross(v1, v2, v1);
      vtkMath::Add(n, v1, n);
      std::swap(v1, v2);
    }
  }
};

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