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G4Field.hh
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25 //
26 // G4Field
27 //
28 // Class description:
29 //
30 // Abstract class for any kind of Field.
31 // It allows any kind of field (vector, scalar, tensor and any set of them)
32 // to be defined by implementing the inquiry function interface.
33 //
34 // The key method is GetFieldValue( const double Point[4],
35 // ************* double *fieldArr )
36 // Given an input position/time vector 'Point',
37 // this method must return the value of the field in "fieldArr".
38 //
39 // A field must also specify whether it changes a track's energy:
40 // DoesFieldChangeEnergy()
41 // *********************
42 // A field must co-work with a corresponding Equation of Motion, to
43 // enable the integration of a particle's position, momentum and, optionally,
44 // spin. For this a field and its equation of motion must follow the
45 // same convention for the order of field components in the array "fieldArr"
46 
47 // Created: John Apostolakis, 10.03.1997
48 // -------------------------------------------------------------------
49 #ifndef G4FIELD_HH
50 #define G4FIELD_HH
51 
52 #include "G4Types.hh"
53 #include "globals.hh"
54 
55 class G4Field
56 {
57  public: // with description
58 
59  G4Field( G4bool gravityOn = false);
60  G4Field( const G4Field& );
61  virtual ~G4Field();
62  G4Field& operator = (const G4Field& p);
63 
64  virtual void GetFieldValue( const G4double Point[4],
65  G4double* fieldArr ) const = 0;
66  // Given the position time vector 'Point',
67  // return the value of the field in the array fieldArr.
68  // Notes:
69  // 1) The 'Point' vector has the following structure:
70  // Point[0] is x ( position, in Geant4 units )
71  // Point[1] is y
72  // Point[2] is z
73  // Point[3] is t ( time, in Geant4 units )
74  // 2) The convention for the components of the field
75  // array 'fieldArr' are determined by the type of field.
76  // See for example the class G4ElectroMagneticField.
77 
78  virtual G4bool DoesFieldChangeEnergy() const = 0;
79  // Each type/class of field should respond this accordingly
80  // For example:
81  // - an electric field should return "true"
82  // - a pure magnetic field should return "false"
83 
84  inline G4bool IsGravityActive() const;
85  // Does this field include gravity?
86 
87  inline void SetGravityActive( G4bool OnOffFlag );
88 
89  virtual G4Field* Clone() const;
90  // Implements cloning, needed by multi-threading
91 
92  static constexpr G4int MAX_NUMBER_OF_COMPONENTS = 24;
93 
94  private:
95 
97 };
98 
99 // Inline methods ...
100 
102 {
103  return fGravityActive;
104 }
105 
106 inline void G4Field::SetGravityActive( G4bool OnOffFlag )
107 {
108  fGravityActive = OnOffFlag;
109 }
110 
111 #endif