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G4RandomDirection.hh
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27 // $Id: G4RandomDirection.hh 96120 2016-03-16 20:29:21Z gcosmo $
28 //
29 //
30 // ------------------------------------------------------------
31 // GEANT 4 class header file
32 // ------------------------------------------------------------
33 // Class description:
34 //
35 // Function returning a unit 3-vector homogeneously randomised over 4pi
36 // solid angle. It can be used in any particle scattering methods
37 // instead of:
38 // z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQRT(1-R1*R1)*COS(2*pi*R2)
39 // providing more performant results.
40 
41 // History:
42 // 15.03.16 E. Tcherniaev, removed unnecessary if and unit()
43 // 18.03.08 V. Grichine, unit radius sphere surface based algorithm
44 // ~ 2007 M. Kossov, algorithm based on 8 Quadrants technique
45 //
46 // ------------------------------------------------------------
47 #ifndef G4RANDOMDIR_HH
48 #define G4RANDOMDIR_HH
49 
51 
52 #include "globals.hh"
53 #include "Randomize.hh"
54 #include "G4ThreeVector.hh"
55 
57 {
58  G4double z = 2.*G4UniformRand() - 1.; // z = cos(theta)
59  G4double rho = std::sqrt((1.+z)*(1.-z)); // rho = sqrt(1-z*z)
61  return G4ThreeVector(rho*std::cos(phi), rho*std::sin(phi), z);
62 }
63 
64 #endif /* G4RANDOMDIR_HH */
CLHEP::Hep3Vector G4ThreeVector
G4ThreeVector G4RandomDirection()
#define G4UniformRand()
Definition: Randomize.hh:97
tuple z
Definition: test.py:28
double G4double
Definition: G4Types.hh:76
static constexpr double twopi
Definition: SystemOfUnits.h:55