text: /*=========================================================================
  
    Program:   Visualization Toolkit
    Module:    vtkBiQuadraticTriangle.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   vtkBiQuadraticTriangle
   * @brief   cell represents a parabolic, isoparametric triangle
   *
   * vtkBiQuadraticTriangle is a concrete implementation of vtkNonLinearCell to
   * represent a two-dimensional, 7-node, isoparametric parabolic triangle. The
   * interpolation is the standard finite element, bi-quadratic isoparametric
   * shape function. The cell includes three mid-edge nodes besides the three
   * triangle vertices and a center node. The ordering of the three points defining the cell is
   * point ids (0-2,3-6) where id #3 is the midedge node between points
   * (0,1); id #4 is the midedge node between points (1,2); and id #5 is the
   * midedge node between points (2,0). id #6 is the center node of the cell.
   *
   * @sa
   * vtkTriangle vtkQuadraticTriangle
   * vtkBiQuadraticQuad vtkBiQuadraticQuadraticWedge vtkBiQuadraticQuadraticHexahedron
   * @par Thanks:
   * <verbatim>
   * This file has been developed by Oxalya - www.oxalya.com
   * Copyright (c) EDF - www.edf.fr
   * </verbatim>
  */
  
  #ifndef vtkBiQuadraticTriangle_h
  #define vtkBiQuadraticTriangle_h
  
  #include "vtkCommonDataModelModule.h" // For export macro
  #include "vtkNonLinearCell.h"
  
  class vtkQuadraticEdge;
  class vtkTriangle;
  class vtkDoubleArray;
  
  class VTKCOMMONDATAMODEL_EXPORT vtkBiQuadraticTriangle : public vtkNonLinearCell
  {
  public:
    static vtkBiQuadraticTriangle *New();
    vtkTypeMacro(vtkBiQuadraticTriangle,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_BIQUADRATIC_TRIANGLE;};
    int GetCellDimension() override {return 2;}
    int GetNumberOfEdges() override {return 3;}
    int GetNumberOfFaces() override {return 0;}
    vtkCell *GetEdge(int edgeId) override;
    vtkCell *GetFace(int) override {return nullptr;}
    //@}
  
    int CellBoundary(int subId, 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(double x[3], double* closestPoint,
                         int& subId, double pcoords[3],
                         double& dist2, double *weights) override;
    void EvaluateLocation(int& subId, double pcoords[3], double x[3],
                          double *weights) override;
    int Triangulate(int index, vtkIdList *ptIds, vtkPoints *pts) override;
    void Derivatives(int subId, double pcoords[3], double *values,
                     int dim, double *derivs) override;
    double *GetParametricCoords() override;
  
    /**
     * Clip this quadratic triangle using scalar value provided. Like
     * contouring, except that it cuts the triangle 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(double p1[3], double p2[3], double tol, double& t,
                          double x[3], double pcoords[3], int& subId) override;
  
  
    /**
     * Return the center of the quadratic triangle in parametric coordinates.
     */
    int GetParametricCenter(double pcoords[3]) override;
  
    /**
     * Return the distance of the parametric coordinate provided to the
     * cell. If inside the cell, a distance of zero is returned.
     */
    double GetParametricDistance(double pcoords[3]) override;
  
    /**
     * @deprecated Replaced by vtkBiQuadraticTriangle::InterpolateFunctions as of VTK 5.2
     */
    static void InterpolationFunctions(double pcoords[3], double weights[7]);
    /**
     * @deprecated Replaced by vtkBiQuadraticTriangle::InterpolateDerivs as of VTK 5.2
     */
    static void InterpolationDerivs(double pcoords[3], double derivs[14]);
    //@{
    /**
     * Compute the interpolation functions/derivatives
     * (aka shape functions/derivatives)
     */
    void InterpolateFunctions(double pcoords[3], double weights[7]) override
    {
      vtkBiQuadraticTriangle::InterpolationFunctions(pcoords,weights);
    }
    void InterpolateDerivs(double pcoords[3], double derivs[14]) override
    {
      vtkBiQuadraticTriangle::InterpolationDerivs(pcoords,derivs);
    }
    //@}
  
  protected:
    vtkBiQuadraticTriangle();
    ~vtkBiQuadraticTriangle() override;
  
    vtkQuadraticEdge *Edge;
    vtkTriangle      *Face;
    vtkDoubleArray   *Scalars; //used to avoid New/Delete in contouring/clipping
  
  private:
    vtkBiQuadraticTriangle(const vtkBiQuadraticTriangle&) = delete;
    void operator=(const vtkBiQuadraticTriangle&) = delete;
  };
  //----------------------------------------------------------------------------
  inline int vtkBiQuadraticTriangle::GetParametricCenter(double pcoords[3])
  {
    pcoords[0] = pcoords[1] = 1./3;
    pcoords[2] = 0.0;
    return 0;
  }
  
  
  #endif
  
  
  