Method DeCasteljauSimplex

Common/DataModel/vtkBezierInterpolation.cxx:174–221

FIXME this could be greatly optimized

// FIXME this could be greatly optimized
void vtkBezierInterpolation::DeCasteljauSimplex(
  int dim, int deg, const double pcoords[3], double* weights)
{
  const int basis_func_n = NumberOfSimplexFunctions(dim, deg);

  const std::array<double, 4> linear_basis = (dim == 2)
    ? std::array<double, 4>{ 1 - pcoords[0] - pcoords[1], pcoords[0], pcoords[1], 0 }
    : std::array<double, 4>{ 1 - pcoords[0] - pcoords[1] - pcoords[2], pcoords[0], pcoords[1],
        pcoords[2] };
  constexpr int lin_degree = 1;
  const int sub_degree_length_max = NumberOfSimplexFunctions(dim, deg - 1);
  const int shape_func_length = NumberOfSimplexFunctions(dim, lin_degree);

  std::vector<double> coeffs(basis_func_n);
  std::vector<double> sub_coeffs(sub_degree_length_max);
  std::vector<double> shape_funcs(shape_func_length);

  for (int bi = 0; bi < basis_func_n; ++bi)
  {
    std::fill(coeffs.begin(), coeffs.end(), 0.0);
    coeffs[bi] = 1.0;

    for (int d = deg; d > 0; --d)
    {
      const int sub_degree = d - 1;
      const int sub_degree_length = NumberOfSimplexFunctions(dim, sub_degree);
      iterateSimplex(dim, sub_degree,
        [&](vtkVector3i sub_degree_coord, int sub_index)
        {
          iterateSimplex(dim, lin_degree,
            [&](vtkVector3i lin_degree_coord, int lin_index)
            {
              const vtkVector3i one_higher_coord = { sub_degree_coord[0] + lin_degree_coord[0],
                sub_degree_coord[1] + lin_degree_coord[1],
                sub_degree_coord[2] + lin_degree_coord[2] };
              const int idx = FlattenSimplex(dim, sub_degree + 1, one_higher_coord);
              shape_funcs[lin_index] = coeffs[idx] * linear_basis[lin_index];
            });
          sub_coeffs[sub_index] = std::accumulate(shape_funcs.begin(), shape_funcs.end(), 0.);
        });
      for (int i = 0; i < sub_degree_length; ++i)
      {
        coeffs[i] = sub_coeffs[i];
      }
    }
    weights[bi] = coeffs[0];
  }
}

void vtkBezierInterpolation::DeCasteljauSimplexDeriv(
  int dim, int deg, const double pcoords[3], double* weights)