G4Field

Directory: source/geometry/magneticfield/include
File Name: G4Field.hh

Class Description :

  
  
   Abstract class for any kind of Field.
   It allows any kind of field (vector, scalar, tensor and any set of them)
   to be defined by implementing the inquiry function interface.
  
   The key method is  GetFieldValue( const  double Point[4],
                      *************         double *fieldArr ) 
   Given an input position/time vector 'Point', 
   this method must return the value of the field in "fieldArr".
  
   A field must also specify whether it changes a track's energy:
                      DoesFieldChangeEnergy() 
                      *********************
   A field must co-work with a corresponding Equation of Motion, to
   enable the integration of a particle's position, momentum and, optionally, 
   spin.  For this a field and its equation of motion must follow the
   same convention for the order of field components in the array "fieldArr"
   -------------------------------------------------------------------
   History:
   - Created:  John Apostolakis, 10.03.1997
   - Modified: 
     V. Grichine     8 Nov 2001: Extended "Point" arg to [4] array to add time
     J. Apostolakis  5 Nov 2003: Added virtual method DoesFieldChangeEnergy()
     J. Apostolakis 31 Aug 2004: Information on convention for components
   -------------------------------------------------------------------

Public members :

      virtual void  GetFieldValue( const  double Point[4],
                                          double *fieldArr ) const = 0;
       // Given the position time vector 'Point', 
       // return the value of the field in the array fieldArr.
       //  Notes: 
       //   1) The 'Point' vector has the following structure:
       //        Point[0]  is  x  ( position, in Geant4 units )
       //        Point[1]  is  y
       //        Point[2]  is  z
       //        Point[3]  is  t  ( time,  in Geant4 units )
       //   2) The convention for the components of the field
       //      array 'fieldArr' are determined by the type of field.
       //      See for example the class G4ElectroMagneticField.

      G4Field( G4bool gravityOn= false);
      G4Field( const G4Field & );
      virtual ~G4Field();
      inline G4Field& operator = (const G4Field &p); 

     // A field signature function that can be used to insure
     // that the Equation of motion object and the G4Field object
     // have the same "field signature"?
 
      virtual G4bool   DoesFieldChangeEnergy() const= 0 ;
       //  Each type/class of field should respond this accordingly
       //  For example:
       //    - an electric field     should return "true"
       //    - a pure magnetic field should return "false"

      G4bool   IsGravityActive() const 
       //  Does this field include gravity?
      inline void SetGravityActive( G4bool OnOffFlag );