---

Field.cxx

Go to the documentation of this file.

// $Id: Field.cxx,v 1.1.1.1 1999/12/20 22:28:41 burnett Exp $
//
// This file is part of Gismo 2
//
//
//    Implementation of class Field member functions
//


#include "gismo/Field.h"

#include "geometry/Ray.h"
#include "geometry/Helix.h"
#include "gismo/Units.h"

#include "facilities/error.h"
#include <float.h>
#include <string.h>

Field::Field_list Field::theFields;     // a list of unique fields


Field::Field(double bx, double by, double bz)
  : constB(bx,by,bz)
{
    checkAppend();
}

Field::Field():constB(0,0,0),id(0){}

void Field::checkAppend()
{

    // check to see if it already exists
    for(id = 0; id<theFields.size(); id++)
        if(theFields[id]->constB == constB)
            break;

    if( id == theFields.size() )
        theFields.push_back(this);

}

Ray*
Field::CreateRay(const Point& r, const Vector& p, float q, float)const
{
  Vector        bField = valueAt(r);
  float         bMag = bField.magnitude();
  float       pmag = p.magnitude();
  if (pmag == 0.) return 0;
  Vector  t=  p.unit() ;


    // --- Neutral Particle or no field: straight line Ray

  if (q == 0 || bMag < 0.001 )
    return new Ray(r, t);

  // --- otherwise the Helix

  Vector    bHat = bField.unit();  // unit vector in direction of field

  float pPerp = pmag * (bHat.cross(t)).mag();
  float rho = pPerp/ ( Units::ec() * q * bMag );
  if(fabs(rho) < 1000.* FLT_EPSILON ) return new Ray(r, t);
  else                                return new Helix(r, t, bHat, rho);

}

void Field::printOn( std::ostream& os ) const
{
 //  printing function, uses C++ ostream class object
        os << "Magnetic Field Base Class: constant field = " << constB << "\n";
}

---