G4Parabola.icc

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// $Id$
//
// --------------------------------------------------------------------
// GEANT 4 inline definitions file
//
// G4Parabola.icc
//
// Implementation of inline methods of G4Parabola
// --------------------------------------------------------------------

inline
void G4Parabola::Init(const G4Axis2Placement3D& position0,
                      G4double focalDist0)
{
  position= position0;
  focalDist= focalDist0;

  // focus
  F= position.GetLocation()+focalDist*position.GetPX();
  // line
  L0= position.GetLocation()-focalDist*position.GetPX();
  //l= position.GetPY();
}

inline
G4double G4Parabola::GetFocalDist() const
{
  return focalDist;
}


inline
G4double G4Parabola::GetPMax() const
{
  return -1;
}

inline
G4Point3D G4Parabola::GetPoint(G4double param) const
{
  return G4Point3D( position.GetLocation()
                    + focalDist* (param*param*position.GetPX()
                    + 2*param*position.GetPY()) );
}

inline
G4double G4Parabola::GetPPoint(const G4Point3D& pt) const
{
  G4Point3D ptLocal= position.GetToPlacementCoordinates()*pt;
  return ptLocal.y()/(2*focalDist);
}


/*
#include "G4CurveRayIntersection.hh"

inline
void G4Parabola::IntersectRay2D(const G4Ray& ray,
                                G4CurveRayIntersection& is)
{
  is.Init(*this, ray);

  const G4Point3D& S= ray.GetStart();
  const G4Vector3D& d= ray.GetDir();

  const G4Vector3D& l= position.GetPY();

  // a == 1
  G4Vector3D SMinusF= S-F;
  G4double bHalf= SMinusF*d - (d.x()*l.y()-d.y()*l.x());
  G4double c= SMinusF.mag2() + ( (S.x()-L0.x())*l.y() - (S.y()-L0.y())*l.x() );

  G4double discr= bHalf*bHalf-c;
  if (discr >= 0) {

    // 2 intersections (maybe 1, but this case is rare)
    G4double sqrtdiscr= std::sqrt(discr);
    // find the smallest positive i
    G4double i= -bHalf-sqrtdiscr;
    if (i<kCarTolerance) {
      i= -bHalf+sqrtdiscr;
      if (i<kCarTolerance) {
        return;
      }
    }
    G4CurveRayIntersection isTmp(*this, ray);
    isTmp.ResetDistance(i);
    is.Update(isTmp);

  }
}
*/

inline
G4int G4Parabola::IntersectRay2D(const G4Ray& ray)
{
  // NOT VERIFIED

  const G4Point3D&  S= ray.GetStart();
  const G4Vector3D& d= ray.GetDir();
  const G4Vector3D& l= position.GetPY();

  // a == 1
  G4Vector3D SMinusF= G4Vector3D( S-F );
  G4double bHalf= SMinusF*d - (d.x()*l.y()-d.y()*l.x());
  G4double c= SMinusF.mag2() + ( (S.x()-L0.x())*l.y() - (S.y()-L0.y())*l.x() );

  G4int nbinter = 0;

  G4double discr= bHalf*bHalf-c;
  if (discr >= 0) 
  {
    // 2 intersections (maybe 1, but this case is rare)
    G4double sqrtdiscr= std::sqrt(discr);
    
    G4double i= -bHalf-sqrtdiscr;
    if (i>kCarTolerance) 
      nbinter++;  
     
    i= -bHalf+sqrtdiscr;
    if (i>kCarTolerance) 
      nbinter++;        
  }

  return nbinter++; 
}

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