Method ComputeNormal

Common/DataModel/vtkPolygon.cxx:198–219

Compute the polygon normal from a points list, and a list of point ids that index into the points list. Parameter pts can be nullptr, indicating that the polygon indexing is {0, 1, ..., numPts-1}. This version will handle non-convex polygons.

// the polygon indexing is {0, 1, ..., numPts-1}. This version will handle
// non-convex polygons.
vtkCellStatus vtkPolygon::ComputeNormal(vtkPoints* p, int numPts, const vtkIdType* pts, double* n)
{
  //
  // Check for special triangle case. Saves extra work.
  //
  n[0] = n[1] = n[2] = 0.0;
  if (numPts < 3)
  {
    return vtkCellStatus::WrongNumberOfPoints;
  }

  if (pts)
  {
    ::ComputeNormal<true>(p, numPts, pts, n);
  }
  else
  {
    ::ComputeNormal<false>(p, numPts, pts, n);
  }

  return (vtkMath::Normalize(n) == 0) ? vtkCellStatus::DegenerateFaces : vtkCellStatus::Valid;
}

//------------------------------------------------------------------------------
// Compute the polygon normal from a points list, and a list of point ids