Method UpdateTensorEigenfunctions

Interaction/Widgets/vtkTensorRepresentation.cxx:1319–1341

------------------------------------------------------------------------------

//------------------------------------------------------------------------------
void vtkTensorRepresentation::UpdateTensorEigenfunctions(double tensor[3][3])
{
  // Now update the tensor information. The tensor data is sorted
  // from largest to smallest eigenvalues.
  double n[3]; // eigenvector norms
  int order[3] = { -1, -1, -1 };
  n[0] = vtkMath::Norm(tensor[0]);
  n[1] = vtkMath::Norm(tensor[1]);
  n[2] = vtkMath::Norm(tensor[2]);
  // NOLINTNEXTLINE(readability-avoid-nested-conditional-operator)
  order[0] = (n[0] >= n[1] ? (n[0] >= n[2] ? 0 : 2) : (n[1] >= n[2] ? 1 : 2)); // max
  // NOLINTNEXTLINE(readability-avoid-nested-conditional-operator)
  order[2] = (n[0] < n[1] ? (n[0] < n[2] ? 0 : 2) : (n[1] < n[2] ? 1 : 2)); // min
  order[1] = 3 - order[0] - order[2];                                       // neat trick ;-)

  this->Eigenvalues[0] = n[order[0]];
  this->Eigenvalues[1] = n[order[1]];
  this->Eigenvalues[2] = n[order[2]];

  std::copy(tensor[order[0]], tensor[order[0]] + 3, this->Eigenvectors[0]);
  std::copy(tensor[order[1]], tensor[order[1]] + 3, this->Eigenvectors[1]);
  std::copy(tensor[order[2]], tensor[order[2]] + 3, this->Eigenvectors[2]);
}

//------------------------------------------------------------------------------
// Update the tensor ellipsoid, and associated widget/representation from the