/* University College London Dept of Physics Course in C++ 3C59 
| all rights reserved 2000
|
| Utility: The Rod class implementation
|
|
| Author: P.Clarke 
*/

// Random angle generator class sold by Petes Enterprises inc.

#include "Rod.h"
#include "Photon.h"

#define M_PI 3.14159 


//---------------------
// Constructor. Note how we also construct the RanCom object.
Rod::Rod( float sourceEnergy, float electronMass )
  : angleGenerator( sourceEnergy,  electronMass )
  {
    m_sourceEnergy = sourceEnergy ;
    m_electronMass = electronMass ;
  }

 
//---------------------
// Main method to return a new photon to the client with an angle and energy
// corresponding to the true compton scattering distribution
Photon Rod::generatePhoton() 
  {
    // Generate a new random angle
    float angle = angleGenerator.scatter( ) ;

    // Calculate the corresponding energy
    float energy = this->calculateEnergy( angle ) ;

    // Create and return a photon
    Photon p( energy, angle ) ;

    return p ;
}


//--------------------
// This calculates the energy corresponding to the scattering angle
float Rod::calculateEnergy( float angle ) 
  {

     float angleInRadians = angle * M_PI / 180.0 ;

		 float invE = (1.0/m_sourceEnergy) + 
                  (1.0/m_electronMass) - 
                  ( cos( angleInRadians ) / m_electronMass ) ;

		 return 1.0/invE ;
}