text: /*=========================================================================
  
    Program:   Visualization Toolkit
    Module:    vtkQuadraticLinearQuad.h
  
    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.
  
  =========================================================================*/
  /**
   * @class   vtkQuadraticLinearQuad
   * @brief   cell represents a quadratic-linear, 6-node isoparametric quad
   *
   * vtkQuadraticQuad is a concrete implementation of vtkNonLinearCell to
   * represent a two-dimensional, 6-node isoparametric quadratic-linear quadrilateral
   * element. The interpolation is the standard finite element, quadratic-linear
   * isoparametric shape function. The cell includes a mid-edge node for two
   * of the four edges. The ordering of the six points defining
   * the cell are point ids (0-3,4-5) where ids 0-3 define the four corner
   * vertices of the quad; ids 4-7 define the midedge nodes (0,1) and (2,3) .
   *
   * @sa
   * vtkQuadraticEdge vtkQuadraticTriangle vtkQuadraticTetra vtkQuadraticQuad
   * vtkQuadraticHexahedron vtkQuadraticWedge vtkQuadraticPyramid
   *
   * @par Thanks:
   * Thanks to Soeren Gebbert  who developed this class and
   * integrated it into VTK 5.0.
   */
  
  #ifndef vtkQuadraticLinearQuad_h
  #define vtkQuadraticLinearQuad_h
  
  #include "vtkCommonDataModelModule.h" // For export macro
  #include "vtkNonLinearCell.h"
  
  class vtkQuadraticEdge;
  class vtkLine;
  class vtkQuad;
  class vtkDoubleArray;
  
  class VTKCOMMONDATAMODEL_EXPORT vtkQuadraticLinearQuad : public vtkNonLinearCell
  {
  public:
    static vtkQuadraticLinearQuad* New();
    vtkTypeMacro(vtkQuadraticLinearQuad, vtkNonLinearCell);
    void PrintSelf(ostream& os, vtkIndent indent) override;
  
    //@{
    /**
     * Implement the vtkCell API. See the vtkCell API for descriptions
     * of these methods.
     */
    int GetCellType() override { return VTK_QUADRATIC_LINEAR_QUAD; }
    int GetCellDimension() override { return 2; }
    int GetNumberOfEdges() override { return 4; }
    int GetNumberOfFaces() override { return 0; }
    vtkCell* GetEdge(int) override;
    vtkCell* GetFace(int) override { return nullptr; }
    //@}
  
    int CellBoundary(int subId, const double pcoords[3], vtkIdList* pts) override;
    void Contour(double value, vtkDataArray* cellScalars, vtkIncrementalPointLocator* locator,
      vtkCellArray* verts, vtkCellArray* lines, vtkCellArray* polys, vtkPointData* inPd,
      vtkPointData* outPd, vtkCellData* inCd, vtkIdType cellId, vtkCellData* outCd) override;
    int EvaluatePosition(const double x[3], double* closestPoint, int& subId, double pcoords[3],
      double& dist2, double* weights) override;
    void EvaluateLocation(int& subId, const double pcoords[3], double x[3], double* weights) override;
    int Triangulate(int index, vtkIdList* ptIds, vtkPoints* pts) override;
    void Derivatives(
      int subId, const double pcoords[3], const double* values, int dim, double* derivs) override;
    double* GetParametricCoords() override;
  
    /**
     * Clip this quadratic linear quad using scalar value provided. Like
     * contouring, except that it cuts the quad to produce linear triangles.
     */
    void Clip(double value, vtkDataArray* cellScalars, vtkIncrementalPointLocator* locator,
      vtkCellArray* polys, vtkPointData* inPd, vtkPointData* outPd, vtkCellData* inCd,
      vtkIdType cellId, vtkCellData* outCd, int insideOut) override;
  
    /**
     * Line-edge intersection. Intersection has to occur within [0,1] parametric
     * coordinates and with specified tolerance.
     */
    int IntersectWithLine(const double p1[3], const double p2[3], double tol, double& t, double x[3],
      double pcoords[3], int& subId) override;
  
    /**
     * Return the center of the pyramid in parametric coordinates.
     */
    int GetParametricCenter(double pcoords[3]) override;
  
    /**
     * @deprecated Replaced by vtkQuadraticLinearQuad::InterpolateFunctions as of VTK 5.2
     */
    static void InterpolationFunctions(const double pcoords[3], double weights[6]);
    /**
     * @deprecated Replaced by vtkQuadraticLinearQuad::InterpolateDerivs as of VTK 5.2
     */
    static void InterpolationDerivs(const double pcoords[3], double derivs[12]);
    //@{
    /**
     * Compute the interpolation functions/derivatives
     * (aka shape functions/derivatives)
     */
    void InterpolateFunctions(const double pcoords[3], double weights[6]) override
    {
      vtkQuadraticLinearQuad::InterpolationFunctions(pcoords, weights);
    }
    void InterpolateDerivs(const double pcoords[3], double derivs[12]) override
    {
      vtkQuadraticLinearQuad::InterpolationDerivs(pcoords, derivs);
    }
    //@}
    /**
     * Return the ids of the vertices defining edge (`edgeId`).
     * Ids are related to the cell, not to the dataset.
     */
    static int* GetEdgeArray(int edgeId);
  
  protected:
    vtkQuadraticLinearQuad();
    ~vtkQuadraticLinearQuad() override;
  
    vtkQuadraticEdge* Edge;
    vtkLine* LinEdge;
    vtkQuad* Quad;
    vtkDoubleArray* Scalars;
  
  private:
    vtkQuadraticLinearQuad(const vtkQuadraticLinearQuad&) = delete;
    void operator=(const vtkQuadraticLinearQuad&) = delete;
  };
  //----------------------------------------------------------------------------
  inline int vtkQuadraticLinearQuad::GetParametricCenter(double pcoords[3])
  {
    pcoords[0] = pcoords[1] = 0.5;
    pcoords[2] = 0.;
    return 0;
  }
  
  #endif
  