Geant4  9.6.p02
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G4RandomTools.hh
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25 //
26 //
27 // $Id$
28 //
29 //
30 // ---------------------------------------------------------------------------
31 // GEANT 4 class header file
32 // ---------------------------------------------------------------------------
33 // Class description:
34 //
35 // Utility functions
36 
37 // History:
38 //
39 // 07.11.08 - P.Gumplinger, based on implementation in G4OpBoundaryProcess
40 //
41 // ---------------------------------------------------------------------------
42 
43 #ifndef G4RANDOMTOOLS_HH
44 #define G4RANDOMTOOLS_HH
45 
47 
48 #include "globals.hh"
49 #include "Randomize.hh"
50 #include "G4RandomDirection.hh"
51 
52 // ---------------------------------------------------------------------------
53 // Returns a random lambertian unit vector
54 //
56 {
57  G4ThreeVector vect;
58  G4double ndotv;
59 
60  do
61  {
62  vect = G4RandomDirection();
63  ndotv = normal * vect;
64 
65  if (ndotv < 0.0)
66  {
67  vect = -vect;
68  ndotv = -ndotv;
69  }
70 
71  } while (!(G4UniformRand() < ndotv));
72 
73  return vect;
74 }
75 
76 // ---------------------------------------------------------------------------
77 // Chooses a random vector within a plane given by the unit normal
78 //
80 {
81  G4ThreeVector vec1 = normal.orthogonal();
82  G4ThreeVector vec2 = vec1.cross(normal);
83 
84  G4double phi = CLHEP::twopi*G4UniformRand();
85  G4double cosphi = std::cos(phi);
86  G4double sinphi = std::sin(phi);
87 
88  return cosphi * vec1 + sinphi * vec2;
89 }
90 
91 #endif /* G4RANDOMTOOLS_HH */