vtkTriangle.h

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

  Program:   Visualization Toolkit
  Module:    $RCSfile: vtkTriangle.h,v $

  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.

=========================================================================*/
#ifndef __vtkTriangle_h
#define __vtkTriangle_h

#include "vtkCell.h"

#include "vtkMath.h" // Needed for inline methods

class vtkLine;
class vtkQuadric;

class VTK_FILTERING_EXPORT vtkTriangle : public vtkCell
{
public:
  static vtkTriangle *New();
  vtkTypeRevisionMacro(vtkTriangle,vtkCell);
  void PrintSelf(ostream& os, vtkIndent indent);

  vtkCell *GetEdge(int edgeId);


  int GetCellType() {return VTK_TRIANGLE;};
  int GetCellDimension() {return 2;};
  int GetNumberOfEdges() {return 3;};
  int GetNumberOfFaces() {return 0;};
  vtkCell *GetFace(int) {return 0;};
  int CellBoundary(int subId, double pcoords[3], vtkIdList *pts);
  void Contour(double value, vtkDataArray *cellScalars, 
               vtkPointLocator *locator, vtkCellArray *verts,
               vtkCellArray *lines, vtkCellArray *polys, 
               vtkPointData *inPd, vtkPointData *outPd,
               vtkCellData *inCd, vtkIdType cellId, vtkCellData *outCd);
  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 Triangulate(int index, vtkIdList *ptIds, vtkPoints *pts);
  void Derivatives(int subId, double pcoords[3], double *values, 
                   int dim, double *derivs);
  virtual double *GetParametricCoords();


  void Clip(double value, vtkDataArray *cellScalars, 
            vtkPointLocator *locator, vtkCellArray *polys,
            vtkPointData *inPd, vtkPointData *outPd,
            vtkCellData *inCd, vtkIdType cellId, vtkCellData *outCd,
            int insideOut);


  static void InterpolationFunctions(double pcoords[3], double sf[3]);
  static void InterpolationDerivs(double pcoords[3], double derivs[6]);


  int IntersectWithLine(double p1[3], double p2[3], double tol, double& t,
                        double x[3], double pcoords[3], int& subId);

  int GetParametricCenter(double pcoords[3]);

  double GetParametricDistance(double pcoords[3]);


  static void TriangleCenter(double p1[3], double p2[3], double p3[3], 
                             double center[3]);

  static double TriangleArea(double p1[3], double p2[3], double p3[3]);
  

  static double Circumcircle(double  p1[2], double p2[2], double p3[2], 
                            double center[2]);


  static int BarycentricCoords(double x[2], double  x1[2], double x2[2], 
                               double x3[2], double bcoords[3]);
  
  

  static int ProjectTo2D(double x1[3], double x2[3], double x3[3],
                         double v1[2], double v2[2], double v3[2]);


  static void ComputeNormal(vtkPoints *p, int numPts, vtkIdType *pts,
                            double n[3]);

  static void ComputeNormal(double v1[3], double v2[3], double v3[3], double n[3]);


  static void ComputeNormalDirection(double v1[3], double v2[3], double v3[3],
                                     double n[3]);
  

  static int PointInTriangle(double x[3], double x1[3], 
                             double x2[3], double x3[3], 
                             double tol2);


  static void ComputeQuadric(double x1[3], double x2[3], double x3[3],
                             double quadric[4][4]);
  static void ComputeQuadric(double x1[3], double x2[3], double x3[3],
                             vtkQuadric *quadric);
  

protected:
  vtkTriangle();
  ~vtkTriangle();

  vtkLine *Line;

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

//----------------------------------------------------------------------------
inline int vtkTriangle::GetParametricCenter(double pcoords[3])
{
  pcoords[0] = pcoords[1] = 1./3; pcoords[2] = 0.0;
  return 0;
}

//----------------------------------------------------------------------------
inline void vtkTriangle::ComputeNormalDirection(double v1[3], double v2[3], 
                                       double v3[3], double n[3])
{
  double ax, ay, az, bx, by, bz;

  // order is important!!! maintain consistency with triangle vertex order 
  ax = v3[0] - v2[0]; ay = v3[1] - v2[1]; az = v3[2] - v2[2];
  bx = v1[0] - v2[0]; by = v1[1] - v2[1]; bz = v1[2] - v2[2];

  n[0] = (ay * bz - az * by);
  n[1] = (az * bx - ax * bz);
  n[2] = (ax * by - ay * bx);
}

//----------------------------------------------------------------------------
inline void vtkTriangle::ComputeNormal(double v1[3], double v2[3], 
                                       double v3[3], double n[3])
{
  double length;

  vtkTriangle::ComputeNormalDirection(v1, v2, v3, n);

  if ( (length = sqrt((n[0]*n[0] + n[1]*n[1] + n[2]*n[2]))) != 0.0 )
    {
    n[0] /= length;
    n[1] /= length;
    n[2] /= length;
    }
}

//----------------------------------------------------------------------------
inline void vtkTriangle::TriangleCenter(double p1[3], double p2[3], 
                                        double p3[3], double center[3])
{
  center[0] = (p1[0]+p2[0]+p3[0]) / 3.0;
  center[1] = (p1[1]+p2[1]+p3[1]) / 3.0;
  center[2] = (p1[2]+p2[2]+p3[2]) / 3.0;
}

//----------------------------------------------------------------------------
inline double vtkTriangle::TriangleArea(double p1[3], double p2[3], double p3[3])
{
  double a,b,c;
  a = vtkMath::Distance2BetweenPoints(p1,p2);
  b = vtkMath::Distance2BetweenPoints(p2,p3);
  c = vtkMath::Distance2BetweenPoints(p3,p1);
  return (0.25* sqrt(fabs(4.0*a*c - (a-b+c)*(a-b+c))));
} 

#endif

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