/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkHigherOrderInterpolation.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

  This software is distributed WITHOUT ANY WARRANTY; without even
  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
  PURPOSE.  See the above copyright notice for more information.

  =========================================================================*/
#include "vtkHigherOrderInterpolation.h"

#include "vtkDoubleArray.h"
#include "vtkHigherOrderTriangle.h"
#include "vtkHigherOrderWedge.h"
#include "vtkMath.h"
#include "vtkNew.h"
#include "vtkObjectFactory.h"
#include "vtkPoints.h"
#include "vtkVector.h"
#include "vtkVectorOperators.h"

#include <array>
#include <vector>

// vtkStandardNewMacro(vtkHigherOrderInterpolation);

// -----------------------------------------------------------------------------
static constexpr double hexCorner[8][3] = { { 0., 0., 0. }, { +1., 0., 0. }, { +1., +1., 0. },
  { 0., +1., 0. }, { 0., 0., +1. }, { +1., 0., +1. }, { +1., +1., +1. }, { 0., +1., +1. } };

// Edges and faces are always oriented along quad/hexahedron axes,
// not any "cell-local" direction (i.e., faces do not all
// have inward-pointing normals).
static constexpr int hexEdgeCorners[12][5] = {
  // e0 e1    varying-  fixed- parametric coordinate(s)
  { 0, 1, 0, 1, 2 }, { 1, 2, 1, 0, 2 }, { 3, 2, 0, 1, 2 }, { 0, 3, 1, 0, 2 }, { 4, 5, 0, 1, 2 },
  { 5, 6, 1, 0, 2 }, { 7, 6, 0, 1, 2 }, { 4, 7, 1, 0, 2 }, { 0, 4, 2, 0, 1 }, { 1, 5, 2, 0, 1 },
  { 2, 6, 2, 0, 1 }, { 3, 7, 2, 0, 1 }
};

static constexpr int hexFaceCorners[6][7] = {
  // c0 c1 c2 c3    varying- fixed-parametric coordinate(s)
  { 0, 3, 7, 4, 1, 2, 0 },
  { 1, 2, 6, 5, 1, 2, 0 },
  { 0, 1, 5, 4, 0, 2, 1 },
  { 3, 2, 6, 7, 0, 2, 1 },
  { 0, 1, 2, 3, 0, 1, 2 },
  { 4, 5, 6, 7, 0, 1, 2 },
};

static constexpr int hexFaceEdges[6][4] = {
  // e0  e1  e2  e3
  { 3, 11, 7, 8 },
  { 1, 10, 5, 9 },
  { 0, 9, 4, 8 },
  { 2, 10, 6, 11 },
  { 0, 1, 2, 3 },
  { 4, 5, 6, 7 },
};
// -----------------------------------------------------------------------------
static constexpr double wedgeCorner[6][3] = { { 0., 0., 0. }, { +1., 0., 0. }, { 0., +1., 0. },
  { 0., 0., +1. }, { +1., 0., +1. }, { 0., +1., +1. } };

// Edges and faces are always oriented along quad/hexahedron axes,
// not any "cell-local" direction (i.e., faces do not all
// have inward-pointing normals).
static constexpr int wedgeEdgeCorners[9][5] = {
  // e0 e1    varying-  fixed- parametric coordinate(s)
  { 0, 1, 0, 1, 2 }, { 1, 2, -1, -1, 2 }, { 2, 0, 1, 0, 2 },

  { 3, 4, 0, 1, 2 }, { 4, 5, -1, -1, 2 }, { 5, 3, 1, 0, 2 },

  { 0, 3, 2, 0, 1 }, { 1, 4, 2, 0, 1 }, { 2, 5, 2, 0, 1 }
};

static constexpr int wedgeFaceCorners[5][9] = {
  // c0  c1  c2  c3   varying-  fixed-param. coordinate(s)  orientation (0 is negative, 1 is
  // positive)  fixed-param. value (-1=lo, +1=hi)
  { 0, 1, 2, -1, 0, 1, 2, 0, -1 },
  { 3, 4, 5, -1, 0, 1, 2, 1, +1 },

  { 0, 1, 4, 3, 0, 2, 1, 1, -1 },
  { 1, 2, 5, 4, -1, 2, -1, 1, -1 },
  { 2, 0, 3, 5, 1, 2, 0, 1, -1 },
};

static constexpr int wedgeFaceEdges[5][5] = {
  // e0  e1  e2  e3    orientation (<- 1 when implied normal points in, not out)
  { 0, 1, 2, -1, 0 },
  { 3, 4, 5, -1, 1 },

  { 0, 7, 3, 6, 0 },
  { 1, 8, 4, 7, 0 },
  { 2, 8, 5, 6, 0 },
};
// -----------------------------------------------------------------------------

vtkHigherOrderInterpolation::vtkHigherOrderInterpolation() {}

vtkHigherOrderInterpolation::~vtkHigherOrderInterpolation() = default;

void vtkHigherOrderInterpolation::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);
}

int vtkHigherOrderInterpolation::Tensor1ShapeFunctions(const int order[1], const double* pcoords,
  double* shape, void (*function_evaluate_shape_functions)(int, double, double*))
{
  std::vector<double> ll;
  ll.resize(order[0] + 1);
  function_evaluate_shape_functions(order[0], pcoords[0], &ll[0]);
  int sn = 0;

  shape[sn++] = ll[0];
  shape[sn++] = ll[order[0]];
  for (int i = 1; i < order[0]; ++i)
  {
    shape[sn++] = ll[i];
  }
  return order[0] + 1;
}

int vtkHigherOrderInterpolation::Tensor1ShapeDerivatives(const int order[1], const double* pcoords,
  double* derivs, void (*function_evaluate_shape_and_gradient)(int, double, double*, double*))
{
  std::vector<double> dummy(order[0] + 1);
  function_evaluate_shape_and_gradient(order[0], pcoords[0], &dummy[0], derivs);
  return order[0] + 1;
}

/// Quadrilateral shape function computation
int vtkHigherOrderInterpolation::Tensor2ShapeFunctions(const int order[2], const double pcoords[3],
  double* shape, void (*function_evaluate_shape_functions)(int, double, double*))
{
  std::array<std::vector<double>, 2> ll;
  int i, j;

  for (i = 0; i < 2; ++i)
  {
    ll[i].resize(order[i] + 1);
    function_evaluate_shape_functions(order[i], pcoords[i], &ll[i][0]);
  }

  int sn = 0;

  // Corners
  shape[sn++] = ll[0][0] * ll[1][0];
  shape[sn++] = ll[0][order[0]] * ll[1][0];
  shape[sn++] = ll[0][order[0]] * ll[1][order[1]];
  shape[sn++] = ll[0][0] * ll[1][order[1]];

  int sn1 = sn + order[0] + order[1] - 2;
  for (i = 1; i < order[0]; ++i)
  {
    // cout << sn << ", " << sn1 << "\n";
    shape[sn++] = ll[0][i] * ll[1][0];         // Edge 0-1
    shape[sn1++] = ll[0][i] * ll[1][order[1]]; // Edge 2-3
  }

  for (i = 1; i < order[1]; ++i)
  {
    // cout << sn << ", " << sn1 << "\n";
    shape[sn++] = ll[0][order[0]] * ll[1][i]; // Edge 1-2
    shape[sn1++] = ll[0][0] * ll[1][i];       // Edge 3-0
  }
  sn = sn1; // Advance to the end of all edge DOFs.

  for (i = 1; i < order[1]; ++i)
  {
    for (j = 1; j < order[0]; ++j)
    {
      // cout << sn << "\n";
      shape[sn++] = ll[0][j] * ll[1][i]; // Face 0-1-2-3
    }
  }
  return sn;
}

// Quadrilateral shape-function derivatives
int vtkHigherOrderInterpolation::Tensor2ShapeDerivatives(const int order[2],
  const double pcoords[2], double* deriv,
  void (*function_evaluate_shape_and_gradient)(int, double, double*, double*))
{
  std::array<std::vector<double>, 2> ll;
  std::array<std::vector<double>, 2> dd;
  int i, j;

  for (i = 0; i < 2; ++i)
  {
    ll[i].resize(order[i] + 1);
    dd[i].resize(order[i] + 1);
    function_evaluate_shape_and_gradient(order[i], pcoords[i], &ll[i][0], &dd[i][0]);
  }

  int sn = 0;

  // Corners
  deriv[sn++] = dd[0][0] * ll[1][0];
  deriv[sn++] = ll[0][0] * dd[1][0];

  deriv[sn++] = dd[0][order[0]] * ll[1][0];
  deriv[sn++] = ll[0][order[0]] * dd[1][0];

  deriv[sn++] = dd[0][order[0]] * ll[1][order[1]];
  deriv[sn++] = ll[0][order[0]] * dd[1][order[1]];

  deriv[sn++] = dd[0][0] * ll[1][order[1]];
  deriv[sn++] = ll[0][0] * dd[1][order[1]];

  int sn1 = sn + 2 * (order[0] + order[1] - 2);
  for (i = 1; i < order[0]; ++i)
  {
    // cout << sn << ", " << sn1 << "\n";
    deriv[sn++] = dd[0][i] * ll[1][0]; // Edge 0-1
    deriv[sn++] = ll[0][i] * dd[1][0]; // Edge 0-1

    deriv[sn1++] = dd[0][i] * ll[1][order[1]]; // Edge 2-3
    deriv[sn1++] = ll[0][i] * dd[1][order[1]]; // Edge 2-3
  }

  for (i = 1; i < order[1]; ++i)
  {
    // cout << sn << ", " << sn1 << "\n";
    deriv[sn++] = dd[0][order[0]] * ll[1][i]; // Edge 1-2
    deriv[sn++] = ll[0][order[0]] * dd[1][i]; // Edge 1-2

    deriv[sn1++] = dd[0][0] * ll[1][i]; // Edge 3-0
    deriv[sn1++] = ll[0][0] * dd[1][i]; // Edge 3-0
  }
  sn = sn1;
  for (i = 1; i < order[1]; ++i)
  {
    for (j = 1; j < order[0]; ++j)
    {
      // cout << sn << "\n";
      deriv[sn++] = dd[0][j] * ll[1][i]; // Face 0-1-2-3
      deriv[sn++] = ll[0][j] * dd[1][i]; // Face 0-1-2-3
    }
  }
  return sn;
}

/// Hexahedral shape function computation
int vtkHigherOrderInterpolation::Tensor3ShapeFunctions(const int order[3], const double pcoords[3],
  double* shape, void (*function_evaluate_shape_functions)(int, double, double*))
{
  std::array<std::vector<double>, 3> ll;
  int i, j, k;

  for (i = 0; i < 3; ++i)
  {
    ll[i].resize(order[i] + 1);
    function_evaluate_shape_functions(order[i], pcoords[i], &ll[i][0]);
  }

  int sn = 0;

  // Corners
  shape[sn++] = ll[0][0] * ll[1][0] * ll[2][0];
  shape[sn++] = ll[0][order[0]] * ll[1][0] * ll[2][0];
  shape[sn++] = ll[0][order[0]] * ll[1][order[1]] * ll[2][0];
  shape[sn++] = ll[0][0] * ll[1][order[1]] * ll[2][0];
  shape[sn++] = ll[0][0] * ll[1][0] * ll[2][order[2]];
  shape[sn++] = ll[0][order[0]] * ll[1][0] * ll[2][order[2]];
  shape[sn++] = ll[0][order[0]] * ll[1][order[1]] * ll[2][order[2]];
  shape[sn++] = ll[0][0] * ll[1][order[1]] * ll[2][order[2]];

  int sn1, sn2, sn3;
  sn1 = order[0] + order[1] - 2;
  sn2 = sn1 * 2;
  sn3 = sn + sn1 + sn2;
  sn1 += sn;
  sn2 += sn;
  for (i = 1; i < order[0]; ++i)
  {
    // cout << sn << ", " << sn1 << ", " << sn2 << ", " << sn3 << "\n";
    shape[sn++] = ll[0][i] * ll[1][0] * ll[2][0];                // Edge 0-1
    shape[sn1++] = ll[0][i] * ll[1][order[1]] * ll[2][0];        // Edge 2-3
    shape[sn2++] = ll[0][i] * ll[1][0] * ll[2][order[2]];        // Edge 4-5
    shape[sn3++] = ll[0][i] * ll[1][order[1]] * ll[2][order[2]]; // Edge 6-7
  }

  for (i = 1; i < order[1]; ++i)
  {
    // cout << sn << ", " << sn1 << ", " << sn2 << ", " << sn3 << "\n";
    shape[sn++] = ll[0][order[0]] * ll[1][i] * ll[2][0];         // Edge 1-2
    shape[sn1++] = ll[0][0] * ll[1][i] * ll[2][0];               // Edge 3-0
    shape[sn2++] = ll[0][order[0]] * ll[1][i] * ll[2][order[2]]; // Edge 5-6
    shape[sn3++] = ll[0][0] * ll[1][i] * ll[2][order[2]];        // Edge 7-4
  }
  sn = sn3;
  sn1 = order[2] - 1;
  sn2 = sn1 * 2;
  sn3 = sn + sn1 + sn2;
  sn1 += sn;
  sn2 += sn;
  for (i = 1; i < order[2]; ++i)
  {
    // cout << sn << ", " << sn1 << ", " << sn2 << ", " << sn3 << "\n";
    shape[sn++] = ll[0][0] * ll[1][0] * ll[2][i];         // Edge 0-4
    shape[sn1++] = ll[0][order[0]] * ll[1][0] * ll[2][i]; // Edge 1-5
    // Kitware insists on swapping edges 10 and 11 as follows:
    shape[sn2++] = ll[0][order[0]] * ll[1][order[1]] * ll[2][i]; // Edge 2-6
    shape[sn3++] = ll[0][0] * ll[1][order[1]] * ll[2][i];        // Edge 3-7
  }

  sn = sn3;
  sn1 = (order[1] - 1) * (order[2] - 1);
  sn2 = sn1 * 2;
  sn3 = sn + sn2 + (order[2] - 1) * (order[0] - 1);
  sn1 += sn;
  sn2 += sn;
  for (i = 1; i < order[2]; ++i)
  {
    for (j = 1; j < order[1]; ++j)
    {
      // cout << sn << ", " << sn1 << "\n";
      shape[sn++] = ll[0][0] * ll[1][j] * ll[2][i];         // Face 0-4-7-3
      shape[sn1++] = ll[0][order[0]] * ll[1][j] * ll[2][i]; // Face 1-2-6-5
    }
    for (j = 1; j < order[0]; ++j)
    {
      // cout << sn2 << ", " << sn3 << "\n";
      shape[sn2++] = ll[0][j] * ll[1][0] * ll[2][i];        // Face 0-1-5-4
      shape[sn3++] = ll[0][j] * ll[1][order[1]] * ll[2][i]; // Face 2-3-7-6
    }
  }
  sn = sn3;
  sn1 = sn + (order[0] - 1) * (order[1] - 1);
  for (i = 1; i < order[1]; ++i)
  {
    for (j = 1; j < order[0]; ++j)
    {
      // cout << sn << ", " << sn1 << "\n";
      shape[sn++] = ll[0][j] * ll[1][i] * ll[2][0];         // Face 0-1-2-3
      shape[sn1++] = ll[0][j] * ll[1][i] * ll[2][order[2]]; // Face 4-7-6-5
    }
  }
  sn = sn1;
  for (k = 1; k < order[2]; ++k)
  {
    for (j = 1; j < order[1]; ++j)
    {
      for (i = 1; i < order[0]; ++i)
      {
        // cout << sn << "\n";
        shape[sn++] = ll[0][i] * ll[1][j] * ll[2][k]; // Body
      }
    }
  }
  return sn;
}

int vtkHigherOrderInterpolation::Tensor3ShapeDerivatives(const int order[3],
  const double pcoords[3], double* deriv,
  void (*function_evaluate_shape_and_gradient)(int, double, double*, double*))
{
  std::array<std::vector<double>, 3> ll;
  std::array<std::vector<double>, 3> dd;
  int i, j, k;

  for (i = 0; i < 3; ++i)
  {
    ll[i].resize(order[i] + 1);
    dd[i].resize(order[i] + 1);
    function_evaluate_shape_and_gradient(order[i], pcoords[i], &ll[i][0], &dd[i][0]);
  }

  int sn = 0;

  // Corners
  deriv[sn++] = dd[0][0] * ll[1][0] * ll[2][0];
  deriv[sn++] = ll[0][0] * dd[1][0] * ll[2][0];
  deriv[sn++] = ll[0][0] * ll[1][0] * dd[2][0];

  deriv[sn++] = dd[0][order[0]] * ll[1][0] * ll[2][0];
  deriv[sn++] = ll[0][order[0]] * dd[1][0] * ll[2][0];
  deriv[sn++] = ll[0][order[0]] * ll[1][0] * dd[2][0];

  deriv[sn++] = dd[0][order[0]] * ll[1][order[1]] * ll[2][0];
  deriv[sn++] = ll[0][order[0]] * dd[1][order[1]] * ll[2][0];
  deriv[sn++] = ll[0][order[0]] * ll[1][order[1]] * dd[2][0];

  deriv[sn++] = dd[0][0] * ll[1][order[1]] * ll[2][0];
  deriv[sn++] = ll[0][0] * dd[1][order[1]] * ll[2][0];
  deriv[sn++] = ll[0][0] * ll[1][order[1]] * dd[2][0];

  deriv[sn++] = dd[0][0] * ll[1][0] * ll[2][order[2]];
  deriv[sn++] = ll[0][0] * dd[1][0] * ll[2][order[2]];
  deriv[sn++] = ll[0][0] * ll[1][0] * dd[2][order[2]];

  deriv[sn++] = dd[0][order[0]] * ll[1][0] * ll[2][order[2]];
  deriv[sn++] = ll[0][order[0]] * dd[1][0] * ll[2][order[2]];
  deriv[sn++] = ll[0][order[0]] * ll[1][0] * dd[2][order[2]];

  deriv[sn++] = dd[0][order[0]] * ll[1][order[1]] * ll[2][order[2]];
  deriv[sn++] = ll[0][order[0]] * dd[1][order[1]] * ll[2][order[2]];
  deriv[sn++] = ll[0][order[0]] * ll[1][order[1]] * dd[2][order[2]];

  deriv[sn++] = dd[0][0] * ll[1][order[1]] * ll[2][order[2]];
  deriv[sn++] = ll[0][0] * dd[1][order[1]] * ll[2][order[2]];
  deriv[sn++] = ll[0][0] * ll[1][order[1]] * dd[2][order[2]];

  int sn1, sn2, sn3;
  sn1 = 3 * (order[0] + order[1] - 2);
  sn2 = sn1 * 2;
  sn3 = sn + sn1 + sn2;
  sn1 += sn;
  sn2 += sn;
  for (i = 1; i < order[0]; ++i)
  {
    // cout << sn << ", " << sn1 << ", " << sn2 << ", " << sn3 << "\n";
    deriv[sn++] = dd[0][i] * ll[1][0] * ll[2][0]; // Edge 0-1
    deriv[sn++] = ll[0][i] * dd[1][0] * ll[2][0]; // Edge 0-1
    deriv[sn++] = ll[0][i] * ll[1][0] * dd[2][0]; // Edge 0-1

    deriv[sn1++] = dd[0][i] * ll[1][order[1]] * ll[2][0]; // Edge 2-3
    deriv[sn1++] = ll[0][i] * dd[1][order[1]] * ll[2][0]; // Edge 2-3
    deriv[sn1++] = ll[0][i] * ll[1][order[1]] * dd[2][0]; // Edge 2-3

    deriv[sn2++] = dd[0][i] * ll[1][0] * ll[2][order[2]]; // Edge 4-5
    deriv[sn2++] = ll[0][i] * dd[1][0] * ll[2][order[2]]; // Edge 4-5
    deriv[sn2++] = ll[0][i] * ll[1][0] * dd[2][order[2]]; // Edge 4-5

    deriv[sn3++] = dd[0][i] * ll[1][order[1]] * ll[2][order[2]]; // Edge 6-7
    deriv[sn3++] = ll[0][i] * dd[1][order[1]] * ll[2][order[2]]; // Edge 6-7
    deriv[sn3++] = ll[0][i] * ll[1][order[1]] * dd[2][order[2]]; // Edge 6-7
  }

  for (i = 1; i < order[1]; ++i)
  {
    // cout << sn << ", " << sn1 << ", " << sn2 << ", " << sn3 << "\n";
    deriv[sn++] = dd[0][order[0]] * ll[1][i] * ll[2][0]; // Edge 1-2
    deriv[sn++] = ll[0][order[0]] * dd[1][i] * ll[2][0]; // Edge 1-2
    deriv[sn++] = ll[0][order[0]] * ll[1][i] * dd[2][0]; // Edge 1-2

    deriv[sn1++] = dd[0][0] * ll[1][i] * ll[2][0]; // Edge 3-0
    deriv[sn1++] = ll[0][0] * dd[1][i] * ll[2][0]; // Edge 3-0
    deriv[sn1++] = ll[0][0] * ll[1][i] * dd[2][0]; // Edge 3-0

    deriv[sn2++] = dd[0][order[0]] * ll[1][i] * ll[2][order[2]]; // Edge 5-6
    deriv[sn2++] = ll[0][order[0]] * dd[1][i] * ll[2][order[2]]; // Edge 5-6
    deriv[sn2++] = ll[0][order[0]] * ll[1][i] * dd[2][order[2]]; // Edge 5-6

    deriv[sn3++] = dd[0][0] * ll[1][i] * ll[2][order[2]]; // Edge 7-4
    deriv[sn3++] = ll[0][0] * dd[1][i] * ll[2][order[2]]; // Edge 7-4
    deriv[sn3++] = ll[0][0] * ll[1][i] * dd[2][order[2]]; // Edge 7-4
  }
  sn = sn3;
  sn1 = 3 * (order[2] - 1);
  sn2 = sn1 * 2;
  sn3 = sn + sn1 + sn2;
  sn1 += sn;
  sn2 += sn;
  for (i = 1; i < order[2]; ++i)
  {
    // cout << sn << ", " << sn1 << ", " << sn2 << ", " << sn3 << "\n";
    deriv[sn++] = dd[0][0] * ll[1][0] * ll[2][i]; // Edge 0-4
    deriv[sn++] = ll[0][0] * dd[1][0] * ll[2][i]; // Edge 0-4
    deriv[sn++] = ll[0][0] * ll[1][0] * dd[2][i]; // Edge 0-4

    deriv[sn1++] = dd[0][order[0]] * ll[1][0] * ll[2][i]; // Edge 1-5
    deriv[sn1++] = ll[0][order[0]] * dd[1][0] * ll[2][i]; // Edge 1-5
    deriv[sn1++] = ll[0][order[0]] * ll[1][0] * dd[2][i]; // Edge 1-5

    // Kitware insists on swapping edges 10 and 11 as follows:
    deriv[sn2++] = dd[0][order[0]] * ll[1][order[1]] * ll[2][i]; // Edge 2-6
    deriv[sn2++] = ll[0][order[0]] * dd[1][order[1]] * ll[2][i]; // Edge 2-6
    deriv[sn2++] = ll[0][order[0]] * ll[1][order[1]] * dd[2][i]; // Edge 2-6

    deriv[sn3++] = dd[0][0] * ll[1][order[1]] * ll[2][i]; // Edge 3-7
    deriv[sn3++] = ll[0][0] * dd[1][order[1]] * ll[2][i]; // Edge 3-7
    deriv[sn3++] = ll[0][0] * ll[1][order[1]] * dd[2][i]; // Edge 3-7
  }

  sn = sn3;
  sn1 = 3 * (order[1] - 1) * (order[2] - 1);
  sn2 = sn1 * 2;
  sn3 = sn + sn2 + 3 * (order[2] - 1) * (order[0] - 1);
  sn1 += sn;
  sn2 += sn;
  for (i = 1; i < order[2]; ++i)
  {
    for (j = 1; j < order[1]; ++j)
    {
      // cout << sn << ", " << sn1 << "\n";
      deriv[sn++] = dd[0][0] * ll[1][j] * ll[2][i]; // Face 0-4-7-3
      deriv[sn++] = ll[0][0] * dd[1][j] * ll[2][i]; // Face 0-4-7-3
      deriv[sn++] = ll[0][0] * ll[1][j] * dd[2][i]; // Face 0-4-7-3

      deriv[sn1++] = dd[0][order[0]] * ll[1][j] * ll[2][i]; // Face 1-2-6-5
      deriv[sn1++] = ll[0][order[0]] * dd[1][j] * ll[2][i]; // Face 1-2-6-5
      deriv[sn1++] = ll[0][order[0]] * ll[1][j] * dd[2][i]; // Face 1-2-6-5
    }
    for (j = 1; j < order[0]; ++j)
    {
      // cout << sn2 << ", " << sn3 << "\n";
      deriv[sn2++] = dd[0][j] * ll[1][0] * ll[2][i]; // Face 0-1-5-4
      deriv[sn2++] = ll[0][j] * dd[1][0] * ll[2][i]; // Face 0-1-5-4
      deriv[sn2++] = ll[0][j] * ll[1][0] * dd[2][i]; // Face 0-1-5-4

      deriv[sn3++] = dd[0][j] * ll[1][order[1]] * ll[2][i]; // Face 2-3-7-6
      deriv[sn3++] = ll[0][j] * dd[1][order[1]] * ll[2][i]; // Face 2-3-7-6
      deriv[sn3++] = ll[0][j] * ll[1][order[1]] * dd[2][i]; // Face 2-3-7-6
    }
  }
  sn = sn3;
  sn1 = sn + 3 * (order[0] - 1) * (order[1] - 1);
  for (i = 1; i < order[1]; ++i)
  {
    for (j = 1; j < order[0]; ++j)
    {
      // cout << sn << ", " << sn1 << "\n";
      deriv[sn++] = dd[0][j] * ll[1][i] * ll[2][0]; // Face 0-1-2-3
      deriv[sn++] = ll[0][j] * dd[1][i] * ll[2][0]; // Face 0-1-2-3
      deriv[sn++] = ll[0][j] * ll[1][i] * dd[2][0]; // Face 0-1-2-3

      deriv[sn1++] = dd[0][j] * ll[1][i] * ll[2][order[2]]; // Face 4-7-6-5
      deriv[sn1++] = ll[0][j] * dd[1][i] * ll[2][order[2]]; // Face 4-7-6-5
      deriv[sn1++] = ll[0][j] * ll[1][i] * dd[2][order[2]]; // Face 4-7-6-5
    }
  }
  sn = sn1;
  for (k = 1; k < order[2]; ++k)
  {
    for (j = 1; j < order[1]; ++j)
    {
      for (i = 1; i < order[0]; ++i)
      {
        // cout << sn << "\n";
        deriv[sn++] = dd[0][i] * ll[1][j] * ll[2][k]; // Body
        deriv[sn++] = ll[0][i] * dd[1][j] * ll[2][k]; // Body
        deriv[sn++] = ll[0][i] * ll[1][j] * dd[2][k]; // Body
      }
    }
  }
  return sn;
}

void vtkHigherOrderInterpolation::Tensor3EvaluateDerivative(const int order[3],
  const double* pcoords, vtkPoints* points, const double* fieldVals, int fieldDim,
  double* fieldDerivs, void (*function_evaluate_shape_and_gradient)(int, double, double*, double*))
{
  vtkIdType numberOfPoints = points->GetNumberOfPoints();
  this->PrepareForOrder(order, numberOfPoints);
  this->Tensor3ShapeDerivatives(
    order, pcoords, &this->DerivSpace[0], function_evaluate_shape_and_gradient);

  // compute inverse Jacobian
  double *jI[3], j0[3], j1[3], j2[3];
  jI[0] = j0;
  jI[1] = j1;
  jI[2] = j2;
  if (this->JacobianInverse(points, this->DerivSpace.data(), jI) == 0)
  { // jacobian inverse computation failed
    return;
  }

  // now compute derivates of values provided
  for (int k = 0; k < fieldDim; k++) // loop over values per vertex
  {
    double sum[3] = { 0, 0, 0 };
    for (vtkIdType i = 0; i < numberOfPoints; i++) // loop over interp. function derivatives
    {
      // Note the subtle difference between the indexing of this->DerivSpace here and in
      // WedgeEvaluateDerivative.
      double value = fieldVals[fieldDim * i + k];
      sum[0] += this->DerivSpace[3 * i] * value;
      sum[1] += this->DerivSpace[3 * i + 1] * value;
      sum[2] += this->DerivSpace[3 * i + 2] * value;
    }

    for (int j = 0; j < 3; j++) // loop over derivative directions
    {
      fieldDerivs[3 * k + j] = sum[0] * jI[j][0] + sum[1] * jI[j][1] + sum[2] * jI[j][2];
    }
  }
}

/// Wedge shape function computation
void vtkHigherOrderInterpolation::WedgeShapeFunctions(const int order[3],
  const vtkIdType numberOfPoints, const double pcoords[3], double* shape,
  vtkHigherOrderTriangle& tri, void (*function_evaluate_shape_functions)(int, double, double*))
{
  if (order[0] != order[1])
  {
    vtkGenericWarningMacro("Orders 0 and 1 (parametric coordinates of triangle, "
      << order[0] << " and " << order[1] << ") must match.");
    return;
  }

  int rsOrder = order[0];
  int tOrder = order[2];

#ifdef VTK_21_POINT_WEDGE
  if (numberOfPoints == 21 && order[0] == 2)
  {
    const double r = pcoords[0];
    const double s = pcoords[1];
    // the parametric space along this axis is [-1,1] for these calculations
    const double t = 2 * pcoords[2] - 1.;
    const double rsm = 1. - r - s;
    const double rs = r * s;
    const double tp = 1. + t;
    const double tm = 1. - t;

    shape[0] = -0.5 * t * tm * rsm * (1.0 - 2.0 * (r + s) + 3.0 * rs);
    shape[1] = -0.5 * t * tm * (r - 2.0 * (rsm * r + rs) + 3.0 * rsm * rs);
    shape[2] = -0.5 * t * tm * (s - 2.0 * (rsm * s + rs) + 3.0 * rsm * rs);
    shape[3] = 0.5 * t * tp * rsm * (1.0 - 2.0 * (r + s) + 3.0 * rs);
    shape[4] = 0.5 * t * tp * (r - 2.0 * (rsm * r + rs) + 3.0 * rsm * rs);
    shape[5] = 0.5 * t * tp * (s - 2.0 * (rsm * s + rs) + 3.0 * rsm * rs);
    shape[6] = -0.5 * t * tm * rsm * (4.0 * r - 12.0 * rs);
    shape[7] = -0.5 * t * tm * (4.0 * rs - 12.0 * rsm * rs);
    shape[8] = -0.5 * t * tm * rsm * (4.0 * s - 12.0 * rs);
    shape[9] = 0.5 * t * tp * rsm * (4.0 * r - 12.0 * rs);
    shape[10] = 0.5 * t * tp * (4.0 * rs - 12.0 * rsm * rs);
    shape[11] = 0.5 * t * tp * rsm * (4.0 * s - 12.0 * rs);
    shape[12] = tp * tm * rsm * (1.0 - 2.0 * (r + s) + 3.0 * rs);
    shape[13] = tp * tm * (r - 2.0 * (rsm * r + rs) + 3.0 * rsm * rs);
    shape[14] = tp * tm * (s - 2.0 * (rsm * s + rs) + 3.0 * rsm * rs);
    shape[15] = -0.5 * 27.0 * t * tm * rsm * rs;
    shape[16] = 0.5 * 27.0 * t * tp * rsm * rs;
    shape[17] = tp * tm * rsm * (4.0 * r - 12.0 * rs);
    shape[18] = tp * tm * (4.0 * rs - 12.0 * rsm * rs);
    shape[19] = tp * tm * rsm * (4.0 * s - 12.0 * rs);
    shape[20] = 27.0 * tp * tm * rsm * rs;
    return;
  }
#endif

  std::vector<double> ll(tOrder + 1);
  function_evaluate_shape_functions(tOrder, pcoords[2], &ll[0]);
  vtkVector3d triP(pcoords);
  triP[2] = 0;
  const int numtripts = (rsOrder + 1) * (rsOrder + 2) / 2;
  std::vector<double> tt(numtripts);
  tri.GetPoints()->SetNumberOfPoints(numtripts);
  tri.GetPointIds()->SetNumberOfIds(numtripts);
  tri.Initialize();
  tri.InterpolateFunctions(triP.GetData(), &tt[0]);

  int sn;
  // int numPts = numtripts * (tOrder + 1);
  vtkIdType ijk[3];
  for (int kk = 0; kk <= tOrder; ++kk)
  {
    for (int jj = 0; jj <= rsOrder; ++jj)
    {
      ijk[1] = jj;
      for (int ii = 0; ii <= rsOrder - jj; ++ii)
      {
        ijk[0] = ii;
        sn = vtkHigherOrderWedge::PointIndexFromIJK(ii, jj, kk, order);
        if (sn >= 0)
        {
          ijk[2] = rsOrder - ii - jj;
          int tOff = vtkHigherOrderTriangle::Index(ijk, rsOrder);
          shape[sn] = ll[kk] * tt[tOff];
        }
      }
    }
  }
}

/// Wedge shape-function derivative evaluation
void vtkHigherOrderInterpolation::WedgeShapeDerivatives(const int order[3],
  const vtkIdType numberOfPoints, const double pcoords[3], double* derivs,
  vtkHigherOrderTriangle& tri,
  void (*function_evaluate_shape_and_gradient)(int, double, double*, double*))
{
  if (order[0] != order[1])
  {
    vtkGenericWarningMacro("Orders 0 and 1 (parametric coordinates of triangle, "
      << order[0] << " and " << order[1] << ") must match.");
    return;
  }

  int rsOrder = order[0];
  int tOrder = order[2];

  std::vector<double> ll(tOrder + 1);
  std::vector<double> ld(tOrder + 1);
  function_evaluate_shape_and_gradient(tOrder, pcoords[2], &ll[0], &ld[0]);
  vtkVector3d triP(pcoords);
  triP[2] = 0;
  const int numtripts = (rsOrder + 1) * (rsOrder + 2) / 2;
  std::vector<double> tt(numtripts);
  std::vector<double> td(2 * numtripts);
  tri.GetPoints()->SetNumberOfPoints(numtripts);
  tri.GetPointIds()->SetNumberOfIds(numtripts);
  tri.Initialize();
  tri.InterpolateFunctions(triP.GetData(), &tt[0]);
  tri.InterpolateDerivs(triP.GetData(), &td[0]);

  int numPts = numtripts * (tOrder + 1);
#ifdef VTK_21_POINT_WEDGE
  if (numberOfPoints == 21 && order[0] == 2)
  {
    const double r = pcoords[0];
    const double s = pcoords[1];
    // the parametric space along this axis is [-1,1] for these calculations
    const double t = 2 * pcoords[2] - 1.;
    const double tm = t - 1.;
    const double tp = t + 1.;
    const double rsm = 1. - r - s;
    const double rs = r * s;

    // dN/dr
    derivs[0] = 0.5 * t * tm * (-3.0 * rs + 2.0 * r + 2.0 * s + (3.0 * s - 2.0) * rsm - 1.0);
    derivs[1] = -0.5 * t * tm * (3.0 * rs - 4.0 * r - 3.0 * s * rsm + 1.0);
    derivs[2] = -1.5 * s * t * tm * (2 * r + s - 1);
    derivs[3] = 0.5 * t * tp * (-3.0 * rs + 2.0 * r + 2.0 * s + (3.0 * s - 2.0) * rsm - 1.0);
    derivs[4] = -0.5 * t * tp * (3.0 * rs - 4.0 * r - 3.0 * s * rsm + 1.0);
    derivs[5] = -1.5 * s * t * tp * (2 * r + s - 1);
    derivs[6] = 0.5 * t * (12.0 * s - 4.0) * tm * (2 * r + s - 1);
    derivs[7] = 0.5 * s * t * tm * (24.0 * r + 12.0 * s - 8.0);
    derivs[8] = s * t * tm * (12.0 * r + 6.0 * s - 8.0);
    derivs[9] = 0.5 * t * (12.0 * s - 4.0) * tp * (2 * r + s - 1);
    derivs[10] = 0.5 * s * t * tp * (24.0 * r + 12.0 * s - 8.0);
    derivs[11] = s * t * tp * (12.0 * r + 6.0 * s - 8.0);
    derivs[12] = tm * tp * (3.0 * rs - 2.0 * r - 2.0 * s - (3.0 * s - 2.0) * rsm + 1.0);
    derivs[13] = tm * tp * (3.0 * rs - 4.0 * r - 3.0 * s * rsm + 1.0);
    derivs[14] = 3.0 * s * tm * tp * (2 * r + s - 1);
    derivs[15] = 13.5 * s * t * tm * (-2 * r - s + 1);
    derivs[16] = 13.5 * s * t * tp * (-2 * r - s + 1);
    derivs[17] = (12.0 * s - 4.0) * tm * tp * (-2 * r - s + 1);
    derivs[18] = -s * tm * tp * (24.0 * r + 12.0 * s - 8.0);
    derivs[19] = s * tm * tp * (-24.0 * r - 12.0 * s + 16.0);
    derivs[20] = 27.0 * s * tm * tp * (2 * r + s - 1);

    // dN/ds
    derivs[21] = 0.5 * t * tm * (-3.0 * rs + 2.0 * r + 2.0 * s + (3.0 * r - 2.0) * rsm - 1.0);
    derivs[22] = -1.5 * r * t * tm * (r + 2 * s - 1);
    derivs[23] = -0.5 * t * tm * (3.0 * rs - 3.0 * r * rsm - 4.0 * s + 1.0);
    derivs[24] = 0.5 * t * tp * (-3.0 * rs + 2.0 * r + 2.0 * s + (3.0 * r - 2.0) * rsm - 1.0);
    derivs[25] = -1.5 * r * t * tp * (r + 2 * s - 1);
    derivs[26] = -0.5 * t * tp * (3.0 * rs - 3.0 * r * rsm - 4.0 * s + 1.0);
    derivs[27] = r * t * tm * (6.0 * r + 12.0 * s - 8.0);
    derivs[28] = 0.5 * r * t * tm * (12.0 * r + 24.0 * s - 8.0);
    derivs[29] = 0.5 * t * (12.0 * r - 4.0) * tm * (r + 2 * s - 1);
    derivs[30] = r * t * tp * (6.0 * r + 12.0 * s - 8.0);
    derivs[31] = 0.5 * r * t * tp * (12.0 * r + 24.0 * s - 8.0);
    derivs[32] = 0.5 * t * (12.0 * r - 4.0) * tp * (r + 2 * s - 1);
    derivs[33] = tm * tp * (3.0 * rs - 2.0 * r - 2.0 * s - (3.0 * r - 2.0) * rsm + 1.0);
    derivs[34] = 3.0 * r * tm * tp * (r + 2 * s - 1);
    derivs[35] = tm * tp * (3.0 * rs - 3.0 * r * rsm - 4.0 * s + 1.0);
    derivs[36] = 13.5 * r * t * tm * (-r - 2 * s + 1);
    derivs[37] = 13.5 * r * t * tp * (-r - 2 * s + 1);
    derivs[38] = r * tm * tp * (-12.0 * r - 24.0 * s + 16.0);
    derivs[39] = -r * tm * tp * (12.0 * r + 24.0 * s - 8.0);
    derivs[40] = (12.0 * r - 4.0) * tm * tp * (-r - 2 * s + 1);
    derivs[41] = 27.0 * r * tm * tp * (r + 2 * s - 1);

    // dN/dt
    derivs[42] = (2 * t - 1) * rsm * (3.0 * rs - 2.0 * r - 2.0 * s + 1.0);
    derivs[43] = r * (-2 * t + 1) * (-2.0 * r - 3.0 * s * rsm + 1.0);
    derivs[44] = s * (-2 * t + 1) * (-3.0 * r * rsm - 2.0 * s + 1.0);
    derivs[45] = (2 * t + 1) * rsm * (3.0 * rs - 2.0 * r - 2.0 * s + 1.0);
    derivs[46] = -r * (2 * t + 1) * (-2.0 * r - 3.0 * s * rsm + 1.0);
    derivs[47] = -s * (2 * t + 1) * (-3.0 * r * rsm - 2.0 * s + 1.0);
    derivs[48] = -r * (12.0 * s - 4.0) * (2 * t - 1) * rsm;
    derivs[49] = rs * (2 * t - 1) * (12.0 * r + 12.0 * s - 8.0);
    derivs[50] = -s * (12.0 * r - 4.0) * (2 * t - 1) * rsm;
    derivs[51] = -r * (12.0 * s - 4.0) * (2 * t + 1) * rsm;
    derivs[52] = rs * (2 * t + 1) * (12.0 * r + 12.0 * s - 8.0);
    derivs[53] = -s * (12.0 * r - 4.0) * (2 * t + 1) * rsm;
    derivs[54] = -4 * t * rsm * (3.0 * rs - 2.0 * r - 2.0 * s + 1.0);
    derivs[55] = 4. * r * (1. - 3. * s + 3. * s * s + r * (-2. + 3. * s)) * t;
    derivs[56] = 4. * s * t * (-3.0 * r * rsm - 2.0 * s + 1.0);
    derivs[57] = -27. * rs * (-2 * t + 1) * rsm;
    derivs[58] = 27. * rs * (2 * t + 1) * rsm;
    derivs[59] = 4. * r * t * (12.0 * s - 4.0) * rsm;
    derivs[60] = 2. * rs * t * (-24.0 * r - 24.0 * s + 16.0);
    derivs[61] = 4. * s * t * (12.0 * r - 4.0) * rsm;
    derivs[62] = -108. * rs * t * rsm;

    return;
  }
#endif
  vtkIdType ijk[3];
  for (int kk = 0; kk <= tOrder; ++kk)
  {
    for (int jj = 0; jj <= rsOrder; ++jj)
    {
      ijk[1] = jj;
      for (int ii = 0; ii <= rsOrder - jj; ++ii)
      {
        ijk[0] = ii;
        int sn = vtkHigherOrderWedge::PointIndexFromIJK(ii, jj, kk, order);
        if (sn >= 0)
        {
          ijk[2] = rsOrder - ii - jj;
          int tOff = vtkHigherOrderTriangle::Index(ijk, rsOrder);
          derivs[sn] = td[tOff] * ll[kk];
          derivs[sn + numPts] = td[tOff + numtripts] * ll[kk];
          derivs[sn + 2 * numPts] = ld[kk] * tt[tOff];
        }
      }
    }
  }
}

void vtkHigherOrderInterpolation::WedgeEvaluate(const int order[3], const vtkIdType numberOfPoints,
  const double* pcoords, double* fieldVals, int fieldDim, double* fieldAtPCoords,
  vtkHigherOrderTriangle& tri, void (*function_evaluate_shape_functions)(int, double, double*))
{
  this->PrepareForOrder(order, numberOfPoints);
  this->WedgeShapeFunctions(
    order, numberOfPoints, pcoords, &this->ShapeSpace[0], tri, function_evaluate_shape_functions);
  // Loop over components of the field:
  for (int cc = 0; cc < fieldDim; ++cc)
  {
    fieldAtPCoords[cc] = 0.;
    // Loop over shape functions (per-DOF values of the cell):
    for (vtkIdType pp = 0; pp < numberOfPoints; ++pp)
    {
      fieldAtPCoords[cc] += this->ShapeSpace[pp] * fieldVals[fieldDim * pp + cc];
    }
  }
}

void vtkHigherOrderInterpolation::WedgeEvaluateDerivative(const int order[3], const double* pcoords,
  vtkPoints* points, const double* fieldVals, int fieldDim, double* fieldDerivs,
  vtkHigherOrderTriangle& tri,
  void (*function_evaluate_shape_and_gradient)(int, double, double*, double*))
{
  vtkIdType numberOfPoints = points->GetNumberOfPoints();
  this->PrepareForOrder(order, numberOfPoints);
  this->WedgeShapeDerivatives(order, numberOfPoints, pcoords, &this->DerivSpace[0], tri,
    function_evaluate_shape_and_gradient);

  // compute inverse Jacobian
  double *jI[3], j0[3], j1[3], j2[3];
  jI[0] = j0;
  jI[1] = j1;
  jI[2] = j2;
  if (this->JacobianInverseWedge(points, this->DerivSpace.data(), jI) == 0)
  { // jacobian inverse computation failed
    return;
  }

  // now compute derivates of values provided
  for (int k = 0; k < fieldDim; k++) // loop over values per vertex
  {
    double sum[3] = { 0, 0, 0 };
    for (vtkIdType i = 0; i < numberOfPoints; i++) // loop over interp. function derivatives
    {
      double value = fieldVals[fieldDim * i + k];
      sum[0] += this->DerivSpace[i] * value;
      sum[1] += this->DerivSpace[numberOfPoints + i] * value;
      sum[2] += this->DerivSpace[2 * numberOfPoints + i] * value;
    }

    for (int j = 0; j < 3; j++) // loop over derivative directions
    {
      fieldDerivs[3 * k + j] = sum[0] * jI[j][0] + sum[1] * jI[j][1] + sum[2] * jI[j][2];
    }
  }
}

#define VTK_MAX_WARNS 6
int vtkHigherOrderInterpolation::JacobianInverse(
  vtkPoints* points, const double* derivs, double** inverse)
{
  double *m[3], m0[3], m1[3], m2[3];
  double x[3];

  // create Jacobian matrix
  m[0] = m0;
  m[1] = m1;
  m[2] = m2;
  for (int i = 0; i < 3; i++) // initialize matrix
  {
    m0[i] = m1[i] = m2[i] = 0.0;
  }

  vtkIdType numberOfPoints = points->GetNumberOfPoints();
  for (vtkIdType j = 0; j < numberOfPoints; j++)
  {
    points->GetPoint(j, x);
    for (int i = 0; i < 3; i++)
    {
      m0[i] += x[i] * derivs[3 * j];
      m1[i] += x[i] * derivs[3 * j + 1];
      m2[i] += x[i] * derivs[3 * j + 2];
    }
  }

  // now find the inverse
  if (vtkMath::InvertMatrix(m, inverse, 3) == 0)
  {
    static int numWarns = 0;
    if (numWarns++ < VTK_MAX_WARNS)
    {
      vtkErrorMacro(<< "Jacobian inverse not found");
      vtkErrorMacro(<< "Matrix:" << m[0][0] << " " << m[0][1] << " " << m[0][2] << " " << m[1][0]
                    << " " << m[1][1] << " " << m[1][2] << " " << m[2][0] << " " << m[2][1] << " "
                    << m[2][2]);
      return 0;
    }
  }

  return 1;
}

int vtkHigherOrderInterpolation::JacobianInverseWedge(
  vtkPoints* points, const double* derivs, double** inverse)
{
  double *m[3], m0[3], m1[3], m2[3];
  double x[3];

  // create Jacobian matrix
  m[0] = m0;
  m[1] = m1;
  m[2] = m2;
  for (int i = 0; i < 3; i++) // initialize matrix
  {
    m0[i] = m1[i] = m2[i] = 0.0;
  }

  vtkIdType numberOfPoints = points->GetNumberOfPoints();
  for (vtkIdType j = 0; j < numberOfPoints; j++)
  {
    points->GetPoint(j, x);
    for (int i = 0; i < 3; i++)
    {
      m0[i] += x[i] * derivs[j];
      m1[i] += x[i] * derivs[numberOfPoints + j];
      m2[i] += x[i] * derivs[2 * numberOfPoints + j];
    }
  }

  // now find the inverse
  if (vtkMath::InvertMatrix(m, inverse, 3) == 0)
  {
    static int numWarns = 0;
    if (numWarns++ < VTK_MAX_WARNS)
    {
      vtkErrorMacro(<< "Jacobian inverse not found");
      vtkErrorMacro(<< "Matrix:" << m[0][0] << " " << m[0][1] << " " << m[0][2] << " " << m[1][0]
                    << " " << m[1][1] << " " << m[1][2] << " " << m[2][0] << " " << m[2][1] << " "
                    << m[2][2]);
      return 0;
    }
  }

  return 1;
}

vtkVector3d vtkHigherOrderInterpolation::GetParametricHexCoordinates(int vertexId)
{
  return vtkVector3d(hexCorner[vertexId]);
}

vtkVector2i vtkHigherOrderInterpolation::GetPointIndicesBoundingHexEdge(int edgeId)
{
  return vtkVector2i(hexEdgeCorners[edgeId][0], hexEdgeCorners[edgeId][1]);
}

int vtkHigherOrderInterpolation::GetVaryingParameterOfHexEdge(int edgeId)
{
  return hexEdgeCorners[edgeId][2];
}

vtkVector2i vtkHigherOrderInterpolation::GetFixedParametersOfHexEdge(int edgeId)
{
  return vtkVector2i(hexEdgeCorners[edgeId][3], hexEdgeCorners[edgeId][4]);
}

const int* vtkHigherOrderInterpolation::GetPointIndicesBoundingHexFace(int faceId)
{
  return hexFaceCorners[faceId];
}

const int* vtkHigherOrderInterpolation::GetEdgeIndicesBoundingHexFace(int faceId)
{
  return hexFaceEdges[faceId];
}

vtkVector2i vtkHigherOrderInterpolation::GetVaryingParametersOfHexFace(int faceId)
{
  return vtkVector2i(hexFaceCorners[faceId][4], hexFaceCorners[faceId][5]);
}

int vtkHigherOrderInterpolation::GetFixedParameterOfHexFace(int faceId)
{
  return hexFaceCorners[faceId][6];
}

vtkVector3d vtkHigherOrderInterpolation::GetParametricWedgeCoordinates(int vertexId)
{
  return vtkVector3d(wedgeCorner[vertexId]);
}

vtkVector2i vtkHigherOrderInterpolation::GetPointIndicesBoundingWedgeEdge(int edgeId)
{
  return vtkVector2i(wedgeEdgeCorners[edgeId][0], wedgeEdgeCorners[edgeId][1]);
}

int vtkHigherOrderInterpolation::GetVaryingParameterOfWedgeEdge(int edgeId)
{
  return wedgeEdgeCorners[edgeId][2];
}

vtkVector2i vtkHigherOrderInterpolation::GetFixedParametersOfWedgeEdge(int edgeId)
{
  return vtkVector2i(wedgeEdgeCorners[edgeId][3], wedgeEdgeCorners[edgeId][4]);
}

const int* vtkHigherOrderInterpolation::GetPointIndicesBoundingWedgeFace(int faceId)
{
  return wedgeFaceCorners[faceId];
}

/// Return 4 edge ids bounding face (with -1 as last id for triangles) plus a face orientation as
/// the 5th number.
const int* vtkHigherOrderInterpolation::GetEdgeIndicesBoundingWedgeFace(int faceId)
{
  return wedgeFaceEdges[faceId];
}

vtkVector2i vtkHigherOrderInterpolation::GetVaryingParametersOfWedgeFace(int faceId)
{
  return vtkVector2i(wedgeFaceCorners[faceId][4], wedgeFaceCorners[faceId][5]);
}

int vtkHigherOrderInterpolation::GetFixedParameterOfWedgeFace(int faceId)
{
  return wedgeFaceCorners[faceId][6];
}

void vtkHigherOrderInterpolation::AppendCurveCollocationPoints(
  vtkSmartPointer<vtkPoints>& pts, const int order[1])
{
  if (!pts)
  {
    pts = vtkSmartPointer<vtkPoints>::New();
  }

  vtkIdType existing = pts->GetNumberOfPoints();
  vtkIdType np = order[0] + 1;
  pts->SetNumberOfPoints(existing + np);
  vtkVector3d e0(0., 0., 0.);
  vtkVector3d e1(+1., 0., 0.);

  // Insert corner points
  vtkIdType sn = existing;
  pts->SetPoint(sn++, e0.GetData());
  pts->SetPoint(sn++, e1.GetData());

  // Insert edge points
  for (int ii = 1; ii < order[0]; ++ii)
  {
    pts->SetPoint(
      sn++, ii / static_cast<double>(order[0]), 0.0, 0.0 // Force curve to y = z = 0 axis
    );
  }
}

void vtkHigherOrderInterpolation::AppendQuadrilateralCollocationPoints(
  vtkSmartPointer<vtkPoints>& pts, const int order[2])
{
  if (!pts)
  {
    pts = vtkSmartPointer<vtkPoints>::New();
  }

  vtkIdType existing = pts->GetNumberOfPoints();
  vtkIdType np = (order[0] + 1) * (order[1] + 1);
  pts->SetNumberOfPoints(existing + np);
  // Insert corner points
  vtkIdType sn = existing;
  for (int ii = 0; ii < 4; ++ii)
  {
    vtkVector3d cc(hexCorner[ii]);
    cc[2] = 0.0; // Force quad to z = 0 plane
    pts->SetPoint(sn++, cc.GetData());
  }

  // Insert edge points
  for (int ii = 0; ii < 4; ++ii)
  {
    vtkVector3d e0(hexCorner[hexEdgeCorners[ii][0]]);
    vtkVector3d e1(hexCorner[hexEdgeCorners[ii][1]]);
    for (int jj = 1; jj < order[hexEdgeCorners[ii][2]]; ++jj)
    {
      double rr = jj / static_cast<double>(order[hexEdgeCorners[ii][2]]);
      vtkVector3d vv = ((1. - rr) * e0 + rr * e1);
      vv[2] = 0.0; // Force quad to z = 0 plane
      pts->SetPoint(sn++, vv.GetData());
    }
  }

  // Insert face points
  for (int jj = 1; jj < order[1]; ++jj)
  {
    for (int ii = 1; ii < order[0]; ++ii)
    {
      pts->SetPoint(sn++, ii / static_cast<double>(order[0]), jj / static_cast<double>(order[1]),
        0.0 // Force quad to z = 0 plane
      );
    }
  }
}

void vtkHigherOrderInterpolation::AppendHexahedronCollocationPoints(
  vtkSmartPointer<vtkPoints>& pts, const int order[3])
{
  if (!pts)
  {
    pts = vtkSmartPointer<vtkPoints>::New();
  }

  vtkIdType existing = pts->GetNumberOfPoints();
  vtkIdType np = (order[0] + 1) * (order[1] + 1) * (order[2] + 1);
  pts->SetNumberOfPoints(existing + np);
  // Insert corner points
  vtkIdType sn = existing;
  for (int ii = 0; ii < 8; ++ii)
  {
    pts->SetPoint(sn++, hexCorner[ii]);
  }

  // Insert edge points
  for (unsigned ii = 0; ii < sizeof(hexEdgeCorners) / sizeof(hexEdgeCorners[0]); ++ii)
  {
    vtkVector3d e0(hexCorner[hexEdgeCorners[ii][0]]);
    vtkVector3d e1(hexCorner[hexEdgeCorners[ii][1]]);
    for (int jj = 1; jj < order[hexEdgeCorners[ii][2]]; ++jj)
    {
      double rr = jj / static_cast<double>(order[hexEdgeCorners[ii][2]]);
      vtkVector3d vv = ((1. - rr) * e0 + rr * e1);
      pts->SetPoint(sn++, vv.GetData());
    }
  }

  // Insert face points
  for (unsigned kk = 0; kk < sizeof(hexFaceCorners) / sizeof(hexFaceCorners[0]); ++kk)
  {
    vtkVector3d f0(hexCorner[hexFaceCorners[kk][0]]);
    vtkVector3d f1(hexCorner[hexFaceCorners[kk][1]]);
    vtkVector3d f2(hexCorner[hexFaceCorners[kk][2]]);
    vtkVector3d f3(hexCorner[hexFaceCorners[kk][3]]);
    for (int jj = 1; jj < order[hexFaceCorners[kk][5]]; ++jj)
    {
      double ss = jj / static_cast<double>(order[hexFaceCorners[kk][5]]);
      for (int ii = 1; ii < order[hexFaceCorners[kk][4]]; ++ii)
      {
        double rr = ii / static_cast<double>(order[hexFaceCorners[kk][4]]);
        vtkVector3d vv = (1. - ss) * ((1. - rr) * f0 + rr * f1) + ss * ((1. - rr) * f3 + rr * f2);
        pts->SetPoint(sn++, vv.GetData());
      }
    }
  }

  // Insert body points
  for (int kk = 1; kk < order[2]; ++kk)
  {
    for (int jj = 1; jj < order[1]; ++jj)
    {
      for (int ii = 1; ii < order[0]; ++ii)
      {
        pts->SetPoint(sn++, ii / static_cast<double>(order[0]), jj / static_cast<double>(order[1]),
          kk / static_cast<double>(order[2]));
      }
    }
  }
}

void vtkHigherOrderInterpolation::AppendWedgeCollocationPoints(
  vtkSmartPointer<vtkPoints>& pts, const int order[3])
{
  if (!pts)
  {
    pts = vtkSmartPointer<vtkPoints>::New();
  }

  vtkIdType existing = pts->GetNumberOfPoints();
  vtkIdType np =
    (order[0] + 1) * (order[1] + 2) * (order[2] + 1) / 2; // NB: assert(order[0] == order[1])
  pts->SetNumberOfPoints(existing + np);
  // Insert corner points
  vtkIdType sn = existing;
  for (int ii = 0; ii < 6; ++ii)
  {
    pts->SetPoint(sn++, wedgeCorner[ii]);
  }

  int rsOrder = order[0]; // assert(order[0] == order[1])
  int tOrder = order[2];

  // Insert edge points
  for (unsigned ii = 0; ii < sizeof(wedgeEdgeCorners) / sizeof(wedgeEdgeCorners[0]); ++ii)
  {
    vtkVector3d e0(wedgeCorner[wedgeEdgeCorners[ii][0]]);
    vtkVector3d e1(wedgeCorner[wedgeEdgeCorners[ii][1]]);
    int varyingParam = wedgeEdgeCorners[ii][2];
    int edgeOrder = varyingParam >= 0 ? order[varyingParam] : rsOrder;
    for (unsigned jj = 1; jj < static_cast<unsigned>(edgeOrder); ++jj)
    {
      double rr = jj / static_cast<double>(edgeOrder);
      vtkVector3d vv = ((1. - rr) * e0 + rr * e1);
      pts->SetPoint(sn++, vv.GetData());
    }
  }

  // Insert face points
  unsigned nn;
  for (nn = 0; nn < 2; ++nn)
  { // Triangular faces
    vtkVector3d f0(wedgeCorner[wedgeFaceCorners[nn][0]]);
    vtkVector3d f1(wedgeCorner[wedgeFaceCorners[nn][1]]);
    // Note funky f3/f2 numbering here matches quadrilateral/hex code
    // where points are in CCW loop:
    vtkVector3d f3(wedgeCorner[wedgeFaceCorners[nn][2]]);
    vtkVector3d f2 = f0 + (f1 - f0) + (f3 - f0);

    for (int jj = 1; jj < rsOrder; ++jj)
    {
      double ss = jj / static_cast<double>(rsOrder);
      for (int ii = 1; ii < rsOrder - jj; ++ii)
      {
        double rr = ii / static_cast<double>(rsOrder);
        vtkVector3d vv = (1. - ss) * ((1. - rr) * f0 + rr * f1) + ss * ((1. - rr) * f3 + rr * f2);
        pts->SetPoint(sn++, vv.GetData());
      }
    }
  }

  for (; nn < sizeof(wedgeFaceCorners) / sizeof(wedgeFaceCorners[0]); ++nn)
  { // Quadrilateral faces
    vtkVector3d f0(wedgeCorner[wedgeFaceCorners[nn][0]]);
    vtkVector3d f1(wedgeCorner[wedgeFaceCorners[nn][1]]);
    vtkVector3d f2(wedgeCorner[wedgeFaceCorners[nn][2]]);
    vtkVector3d f3(wedgeCorner[wedgeFaceCorners[nn][3]]);

    for (int jj = 1; jj < tOrder; ++jj)
    {
      double ss = jj / static_cast<double>(tOrder);
      for (int ii = 1; ii < rsOrder; ++ii)
      {
        double rr = ii / static_cast<double>(rsOrder);
        vtkVector3d vv = (1. - ss) * ((1. - rr) * f0 + rr * f1) + ss * ((1. - rr) * f3 + rr * f2);
        pts->SetPoint(sn++, vv.GetData());
      }
    }
  }

  // Insert body points
  for (int kk = 1; kk < tOrder; ++kk)
  {
    for (int jj = 1; jj < rsOrder; ++jj)
    {
      for (int ii = 1; ii < rsOrder - jj; ++ii)
      {
        pts->SetPoint(sn++, ii / static_cast<double>(rsOrder), jj / static_cast<double>(rsOrder),
          kk / static_cast<double>(tOrder));
      }
    }
  }
}

#if 0
void vtkHigherOrderInterpolation::AppendWedgeCollocationPoints(vtkPoints* pts, int o1, int o2, int o3)
{
  int o[3] = {o1, o2, o3};
  vtkSmartPointer<vtkPoints> spts(pts);
  vtkHigherOrderInterpolation::AppendWedgeCollocationPoints(spts, o);
}
#endif // 0

void vtkHigherOrderInterpolation::PrepareForOrder(
  const int order[3], const vtkIdType numberOfPoints)
{
  // Ensure some scratch space is allocated for templated evaluation methods.
  std::size_t maxShape =
    numberOfPoints > 0 ? numberOfPoints : ((order[0] + 1) * (order[1] + 1) * (order[2] + 1));
  std::size_t maxDeriv = maxShape * 3;
  if (this->ShapeSpace.size() < maxShape)
  {
    this->ShapeSpace.resize(maxShape);
  }
  if (this->DerivSpace.size() < maxDeriv)
  {
    this->DerivSpace.resize(maxDeriv);
  }
}
