TrkPoca.cxx

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//--------------------------------------------------------------------------
// File and Version Information:
//      $Id: TrkPoca.cxx,v 1.4 2010/09/26 00:31:59 zhangy Exp $
//
// Description:
//
//
// Environment:
//      Software developed for the BaBar Detector at the SLAC B-Factory.
//
// Author(s): Steve Schaffner, largely taken from Art Snyder
//
//------------------------------------------------------------------------
// #include "BaBar/BaBar.h"
#include "TrkBase/TrkPoca.h"
#include "CLHEP/Geometry/Point3D.h"
#include "CLHEP/Matrix/Vector.h"
#include "CLHEP/Vector/ThreeVector.h"
#include "MdcGeom/Trajectory.h"
#include "TrkBase/TrkErrCode.h"
 
TrkPoca::TrkPoca( const Trajectory& traj1, double f1, const Trajectory& traj2, double f2,
                  double prec )
    : TrkPocaBase( f1, f2, prec ), _doca( -9999. ) {
  minimize( traj1, f1, traj2, f2 );
  if ( status().failure() ) return;
  calcDist( traj1, traj2 );
}
 
TrkPoca::TrkPoca( const Trajectory& traj, double flt, const HepPoint3D& pt, double prec )
    : TrkPocaBase( flt, prec ) {
  minimize( traj, flt, pt );
  if ( status().failure() ) return;
  _doca = ( traj.position( flt1() ) - pt ).mag();
}
 
void TrkPoca::calcDist( const Trajectory& traj1, const Trajectory& traj2 ) {
  // Does a final calculation of the distance -- getting the sign right.
  //  In case of (nearly) parallel, returns error and distance.
 
  // A bunch of unsightly uninitialized variables:
  static Hep3Vector dir1, dir2;
  static HepPoint3D pos1, pos2;
 
  traj1.getInfo( flt1(), pos1, dir1 );
  traj2.getInfo( flt2(), pos2, dir2 );
  Hep3Vector delta   = ( (CLHEP::Hep3Vector)pos2 ) - ( (CLHEP::Hep3Vector)pos1 );
  Hep3Vector between = dir1.cross( dir2 ); // cross-product
 
  if ( status().success() != 3 )
  { // Not parallel:
    between = between.unit();
    _doca   = delta.dot( between );
  }
  else
  { // Parallel:
    // Arbitrary sign convention
    double sign = ( dir1.dot( dir2 ) > 0. ) ? -1. : 1.;
    _doca       = ( delta - delta.dot( dir1 ) * dir1 ).mag();
    _doca *= sign;
  }
}