TVirtualMagField.cxx

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// @(#)root/geom:$Id$
 
/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
 
#include "TVirtualMagField.h"
 
#include "TGeoGlobalMagField.h"
 
/** \class TVirtualMagField
\ingroup Geometry_classes
Abstract class for magnetic field. Derived classes are encouraged to
use the TVirtualMagField named constructor and must implement the method:
 
~~~ {.cpp}
   Field(const Double_t *x, Double_t *B)
~~~
 
A field object can be made global via:
 
~~~ {.cpp}
   TGlobalMagField::Instance()->SetField(field)         [1]
~~~
 
A field which is made global is owned by the field manager. The used is not
allowed to delete it directly anymore (otherwise a Fatal() is issued). Global
field can be deleted by calling [1] with a different argument (which can be
NULL). Otherwise the global field is deleted together with the field manager.
*/
 
ClassImp(TVirtualMagField);
 
////////////////////////////////////////////////////////////////////////////////
/// Destructor. Unregisters the field.
 
TVirtualMagField::~TVirtualMagField()
{
   if (TGeoGlobalMagField::GetInstance()) {
      TVirtualMagField *global_field = TGeoGlobalMagField::GetInstance()->GetField();
      if (global_field == this)
         Fatal("~TVirtualMagField", "Not allowed to delete a field once set global. \
                \n To delete the field call: TGeoGlobalMagField::Instance()->SetField(NULL)");
   }
}
 
/** \class TGeoUniformMagField
\ingroup Geometry_classes
 
Implementation for uniform magnetic field.
*/
 
ClassImp(TGeoUniformMagField);
 
////////////////////////////////////////////////////////////////////////////////
/// Default constructor;
 
TGeoUniformMagField::TGeoUniformMagField()
                    :TVirtualMagField()
{
   fB[0] = 0.;
   fB[1] = 0.;
   fB[2] = 0.;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Default constructor;
 
TGeoUniformMagField::TGeoUniformMagField(Double_t Bx, Double_t By, Double_t Bz)
                    :TVirtualMagField("Uniform magnetic field")
{
   fB[0] = Bx;
   fB[1] = By;
   fB[2] = Bz;
}