Reconstruction/MdcPatRec/TrkBase/include/TrkBase/TrkPocaXY.h

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//--------------------------------------------------------------------------
// File and Version Information:
//      $Id: TrkPocaXY.h,v 1.1.1.1 2005/04/21 06:01:42 zhangy Exp $
//
// Description:
//     Calculate the point of closest approach between two trajectories
//     (TrkDifTraj only) or between a trajectory and a point in the XY plane.
//     Calculates (in ctor) the distance and the flight lengths along
//     the trajectory or trajectories;
//     The input flightlengths are used as a starting point;
//     (A good starting point also reduces CPU time.)
//     Note that distance is a signed quantity for two trajectories.
// Environment:
//      Software developed for the BaBar Detector at the SLAC B-Factory.
//
// Author(s): Selenia Dittongo                    Univ. Ferrara
//
//     Dave Brown 3/31/03
//     Re-implemented to use the TrkPoca interface and implementation
//------------------------------------------------------------------------
#ifndef TRKPOCAXY_H
#define TRKPOCAXY_H
 
#include "TrkBase/TrkDifTraj.h"
#include "TrkBase/TrkPocaBase.h"
 
class TrkPocaXY : public TrkPocaBase {
public:
  //  Replace the original constructors with the equivalent, standard TrkPoca interface
  //
  //  TrkPocaXY(const TrkDifTraj& traj1, const double& fltl1,
  //        const TrkDifTraj& traj2, const double& fltl2);
  //
  //  TrkPocaXY(const TrkDifTraj& traj, const double& fltl, const HepPoint& pt);
  TrkPocaXY( const Trajectory& traj, double flt, const HepPoint3D& pt,
             double precision = 1.0e-4 );
 
  TrkPocaXY( const Trajectory& traj1, double flt1, const Trajectory& traj2, double flt2,
             double precision = 1.0e-4 );
 
  ~TrkPocaXY() {}
 
  inline double docaXY() const; // distance of closest approach in XY plane
 
  // provide the following for backwards compatibility.  Code copying is really an ugly thing.
 
  double fltl1() const { return flt1(); }
  double fltl2() const { return flt2(); }
 
private:
  double _docaxy;
 
  void interLineCircle( const double& m, const double& q, const double& xc, const double& yc,
                        const double& radius, double& xint1, double& yint1, double& xint2,
                        double& yint2 );
 
  void interTwoLines( const double& m1, const double& q1, const double& m2, const double& q2,
                      double& xint, double& yint );
 
  void interTwoCircles( const double& xc1, const double& yc1, const double& r1,
                        const double& xc2, const double& yc2, const double& r2, double& xint1,
                        double& yint1, double& xint2, double& yint2 );
};
 
// Inlined functions
double TrkPocaXY::docaXY() const { return _docaxy; }
 
#endif