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

  Program:   Visualization Toolkit
  Module:    vtkTetra.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.

=========================================================================*/
// .NAME vtkTetra - a 3D cell that represents a tetrahedron
// .SECTION Description
// vtkTetra is a concrete implementation of vtkCell to represent a 3D
// tetrahedron. vtkTetra uses the standard isoparametric shape functions
// for a linear tetrahedron. The tetrahedron is defined by the four points
// (0-3); where (0,1,2) is the base of the tetrahedron which, using the
// right hand rule, forms a triangle whose normal points in the direction
// of the fourth point.

// .SECTION See Also
// vtkConvexPointSet vtkHexahedron vtkPyramid vtkVoxel vtkWedge

#ifndef __vtkTetra_h
#define __vtkTetra_h

#include "vtkCell3D.h"

class vtkLine;
class vtkTriangle;
class vtkUnstructuredGrid;

class VTK_COMMON_EXPORT vtkTetra : public vtkCell3D
{
public:
  static vtkTetra *New();
  vtkTypeRevisionMacro(vtkTetra,vtkCell3D);

  // Description:
  // See vtkCell3D API for description of these methods.
  virtual void GetEdgePoints(int edgeId, int* &pts);
  virtual void GetFacePoints(int faceId, int* &pts);

  // Description:
  // See the vtkCell API for descriptions of these methods.
  int GetCellType() {return VTK_TETRA;}
  int GetNumberOfEdges() {return 6;}
  int GetNumberOfFaces() {return 4;}
  vtkCell *GetEdge(int edgeId);
  vtkCell *GetFace(int faceId);
  void Contour(double value, vtkDataArray *cellScalars, 
               vtkPointLocator *locator, vtkCellArray *verts, 
               vtkCellArray *lines, vtkCellArray *polys,
               vtkPointData *inPd, vtkPointData *outPd,
               vtkCellData *inCd, vtkIdType cellId, vtkCellData *outCd);
  void Clip(double value, vtkDataArray *cellScalars, 
            vtkPointLocator *locator, vtkCellArray *connectivity,
            vtkPointData *inPd, vtkPointData *outPd,
            vtkCellData *inCd, vtkIdType cellId, vtkCellData *outCd, 
            int insideOut);
  int EvaluatePosition(double x[3], double* closestPoint,
                       int& subId, double pcoords[3],
                       double& dist2, double *weights);
  void EvaluateLocation(int& subId, double pcoords[3], double x[3],
                        double *weights);
  int IntersectWithLine(double p1[3], double p2[3], double tol, double& t,
                        double x[3], double pcoords[3], int& subId);
  int Triangulate(int index, vtkIdList *ptIds, vtkPoints *pts);
  void Derivatives(int subId, double pcoords[3], double *values, 
                   int dim, double *derivs);
  virtual double *GetParametricCoords();

  // Description:
  // Returns the set of points that are on the boundary of the tetrahedron that
  // are closest parametrically to the point specified. This may include faces,
  // edges, or vertices.
  int CellBoundary(int subId, double pcoords[3], vtkIdList *pts);
  
  // Description:
  // Return the center of the tetrahedron in parametric coordinates.
  int GetParametricCenter(double pcoords[3]);

  // Description:
  // 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]);

  // Description:
  // Compute the center of the tetrahedron,
  static void TetraCenter(double p1[3], double p2[3], double p3[3], double p4[3], 
                          double center[3]);

  // Description:
  // Compute the circumcenter (center[3]) and radius squared (method
  // return value) of a tetrahedron defined by the four points x1, x2,
  // x3, and x4.
  static double Circumsphere(double  p1[3], double p2[3], double p3[3], 
                             double p4[3], double center[3]);

  // Description:
  // Compute the center (center[3]) and radius (method return value) of
  // a sphere that just fits inside the faces of a tetrahedron defined
  // by the four points x1, x2, x3, and x4.
  static double Insphere(double  p1[3], double p2[3], double p3[3], 
                         double p4[3], double center[3]);

  // Description:
  // Given a 3D point x[3], determine the barycentric coordinates of the point.
  // Barycentric coordinates are a natural coordinate system for simplices that
  // express a position as a linear combination of the vertices. For a 
  // tetrahedron, there are four barycentric coordinates (because there are
  // four vertices), and the sum of the coordinates must equal 1. If a 
  // point x is inside a simplex, then all four coordinates will be strictly 
  // positive.  If three coordinates are zero (so the fourth =1), then the 
  // point x is on a vertex. If two coordinates are zero, the point x is on an 
  // edge (and so on). In this method, you must specify the vertex coordinates
  // x1->x4. Returns 0 if tetrahedron is degenerate.
  static int BarycentricCoords(double x[3], double  x1[3], double x2[3], 
                               double x3[3], double x4[3], double bcoords[4]);
  
  // Description:
  // Compute the volume of a tetrahedron defined by the four points
  // p1, p2, p3, and p4.
  static double ComputeVolume(double  p1[3], double p2[3], double p3[3], 
                              double p4[3]);

  // Description:
  // Given parametric coordinates compute inverse Jacobian transformation
  // matrix. Returns 9 elements of 3x3 inverse Jacobian plus interpolation
  // function derivatives. Returns 0 if no inverse exists.
  int JacobianInverse(double **inverse, double derivs[12]);

  // Description:
  // Tetra specific methods.
  static void InterpolationFunctions(double pcoords[3], double weights[4]);
  static void InterpolationDerivs(double derivs[12]);
  static int *GetEdgeArray(int edgeId);
  static int *GetFaceArray(int faceId);

protected:
  vtkTetra();
  ~vtkTetra();

  vtkLine *Line;
  vtkTriangle *Triangle;

private:
  vtkTetra(const vtkTetra&);  // Not implemented.
  void operator=(const vtkTetra&);  // Not implemented.
};

inline int vtkTetra::GetParametricCenter(double pcoords[3])
{
  pcoords[0] = pcoords[1] = pcoords[2] = 0.25;
  return 0;
}

#endif



