JMARKOV::JDirectedSource Class Reference

Implementation of the JSourceModel class that represents a directed source with a flat intensity distribution. More...

#include <JScatteringModel.hh>

Inheritance diagram for JMARKOV::JDirectedSource:

Public Member Functions
	JDirectedSource (JVersor3D _source_dir, double _alpha, bool _cutSurface=false, const JVersor3D _surface_normal=JVersor3D())
	Constructor. More...
double	getOpeningAngle () const
	return the opening angle in radians More...
JVersor3D	getDirection () const
	return the source direction More...
double	getEmissionProbability (JVersor3D dir)
	Return the probability density. More...
JVersor3D	generateDirection ()
	Return a randomly generated direction according to the emission distribution. More...
void	setPosition (JPosition3D &_pos)
const JPosition3D &	getPosition () const

Protected Member Functions
double	getPhiMax (double theta)
	For a given angle theta with respect to the beam direction, and a given surface normal, we define phi as the rotation angle around the beam, where phi=0 corresponds to the direction sticking out over the surface a much as possible. More...

Protected Attributes
JVersor3D	source_dir
double	ctmin
double	alpha
bool	cutSurface
JVersor3D	surface_normal
double	delta
double	omega
JPosition3D	pos

Detailed Description

Implementation of the JSourceModel class that represents a directed source with a flat intensity distribution.

When _cutSurface = true, photons that would be emitted into the surface (defined by the surface normal) will not be emitted.

Definition at line 143 of file JScatteringModel.hh.

Constructor & Destructor Documentation

JMARKOV::JDirectedSource::JDirectedSource ( JVersor3D  _source_dir, double  _alpha, bool  _cutSurface = false, const JVersor3D  _surface_normal = JVersor3D()  )

inline

Constructor.

_source_dir is the source direction _alpha is the opening angle in radians

note that _alpha should be > -1

Definition at line 153 of file JScatteringModel.hh.

                                                                                                                                 :
      source_dir(_source_dir), ctmin(cos(0.5*_alpha)), alpha(_alpha), cutSurface(_cutSurface), surface_normal(_surface_normal) {
      // we have to find out which fraction of photons would be emitted into the surface, given
      // the direction and opening angle
      // as far as I can tell, this is a non-trivial integral, so I solve it numerically

      // delta is the angle of the beam direction over the surface 
      // (negative means the beam points into the surface)
      delta = 0.5*M_PI - acos(surface_normal.getDot(source_dir)) ;
      omega = 2.0*M_PI*(1.0-ctmin) ; // space angle of beam ("spherical cap")

      if( cutSurface ) {
        if( delta>0.0 && delta>0.5*_alpha )  {
          // no part of the beam points into the surface
          //fraction_into_surface = 0.0 ;
        } else if( delta<=0 && fabs(delta)>=0.5*alpha ) {
          // the beam points completely into the surface, throw an error
          //fraction_into_surface = 1.0 ;
          omega = 0.0 ;
          cerr << "FATAL ERROR in JDirectedSource: beam points completely into the surface." << endl ;
          exit(1) ;
        } else {
          // part of the beam points into the surface, which effectively reduces
          // the space angle omega
          // here we numerically compute omega

          // only at theta=delta to alpha/2 is part of the beam absorbed
          // we calculate the space angle of the absorbed beam part
          double omega_absorbed = 0.0 ;
          const int __nct = 100000 ;
          const double __ctmin = cos(0.5*alpha) ;
          const double __ctmax = cos(delta) ;
          const double __dct   = (__ctmax - __ctmin)/__nct ;
          for( int i=0; i<__nct; ++i ) {
            double __ct = __ctmin + (i+0.5) * __dct ;
            double __theta = acos(__ct) ;
            double __phirange = 2.0*(M_PI-getPhiMax(__theta)) ; 
            omega_absorbed += __phirange ;
          }
          omega_absorbed *= __dct ;
          omega -= omega_absorbed ;

          // if the beam direction is into the surface, this part gets absorbed completely
          if( delta<0 ) {
            omega -= 2.0 * M_PI * (1.0-cos(delta)) ;
          }
        }
      }
    }

Member Function Documentation

double JMARKOV::JDirectedSource::getOpeningAngle ( ) const

inline

return the opening angle in radians

Definition at line 204 of file JScatteringModel.hh.

{ return alpha ; }

JVersor3D JMARKOV::JDirectedSource::getDirection ( ) const

inline

return the source direction

Definition at line 207 of file JScatteringModel.hh.

{ return source_dir ; }

double JMARKOV::JDirectedSource::getEmissionProbability ( JVersor3D  dir )

inlinevirtual

Return the probability density.

dP / dOmega = dP / dCosTheta dPhi

that a photon from this source is emitted in a given direction, given that a photon is emitted.

Implements JMARKOV::JSourceModel.

Definition at line 209 of file JScatteringModel.hh.

                                                   {
      double ct = dir.getDot(source_dir) ;
      if( ct>ctmin ) {
        if( cutSurface && dir.getDot(surface_normal)<0 ) return 0.0 ;
        return 1.0/omega ;
      }
      return 0.0 ;
    }

JVersor3D JMARKOV::JDirectedSource::generateDirection ( )

inlinevirtual

Return a randomly generated direction according to the emission distribution.

This uses gRandom.

Implements JMARKOV::JSourceModel.

Definition at line 218 of file JScatteringModel.hh.

                                  {
      while(true) {
        double phi = gRandom->Uniform(0,2*M_PI) ;
        double ct  = gRandom->Uniform(ctmin,1) ;
        JVersor3D _dir( JAngle3D(acos(ct),phi) ) ;      
        JRotation3D R( source_dir ) ; 
        JVersor3D dir(_dir.rotate_back(R)) ;
        if( !cutSurface ) return dir ;
        if( dir.getDot(surface_normal)>0 ) return dir ;
      }
    }

double JMARKOV::JDirectedSource::getPhiMax ( double  theta )

inlineprotected

For a given angle theta with respect to the beam direction, and a given surface normal, we define phi as the rotation angle around the beam, where phi=0 corresponds to the direction sticking out over the surface a much as possible.

This function returns 'phi max', which is the largest value of phi for which the direction does not point into the surface.

Definition at line 241 of file JScatteringModel.hh.

                                     {
      if( delta>0 ) {
        if( theta<delta ) return M_PI ;
        if( theta+delta > M_PI ) return 0.0 ;
      }
      if( delta<0 ) {
        if( theta<fabs(delta) ) return 0.0 ;
        if( theta+fabs(delta) > M_PI ) return M_PI ;
      }
      double phimax = acos(-tan(delta)/tan(theta)) ;
      return phimax ;
    }

void JMARKOV::JSourceModel::setPosition ( JPosition3D &  _pos )

inlineinherited

Definition at line 107 of file JScatteringModel.hh.

{ pos = _pos ; }

const JPosition3D& JMARKOV::JSourceModel::getPosition ( ) const

inlineinherited

Definition at line 109 of file JScatteringModel.hh.

{ return pos ; }

Member Data Documentation

JVersor3D JMARKOV::JDirectedSource::source_dir

protected

Definition at line 255 of file JScatteringModel.hh.

double JMARKOV::JDirectedSource::ctmin

protected

Definition at line 256 of file JScatteringModel.hh.

double JMARKOV::JDirectedSource::alpha

protected

Definition at line 257 of file JScatteringModel.hh.

bool JMARKOV::JDirectedSource::cutSurface

protected

Definition at line 258 of file JScatteringModel.hh.

JVersor3D JMARKOV::JDirectedSource::surface_normal

protected

Definition at line 259 of file JScatteringModel.hh.

double JMARKOV::JDirectedSource::delta

protected

Definition at line 260 of file JScatteringModel.hh.

double JMARKOV::JDirectedSource::omega

protected

Definition at line 262 of file JScatteringModel.hh.

JPosition3D JMARKOV::JSourceModel::pos

protectedinherited

Definition at line 113 of file JScatteringModel.hh.

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The documentation for this class was generated from the following file:

• JScatteringModel.hh