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1 // 1 //
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4 // * 4 // * *
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18 // * This code implementation is the result 18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboratio 19 // * technical work of the GEANT4 collaboration. *
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24 // ******************************************* 24 // ********************************************************************
25 // 25 //
26 // 26 //
>> 27 // $Id: G4RandomDirection.hh 97527 2016-06-03 14:59:04Z gcosmo $
27 // 28 //
28 // << 29 //
29 // ------------------------------------------- 30 // ------------------------------------------------------------
30 // GEANT 4 class header file << 31 // GEANT 4 class header file
31 // ------------------------------------------- 32 // ------------------------------------------------------------
32 // Class description: 33 // Class description:
33 // 34 //
34 // Function returning a unit 3-vector homogene 35 // Function returning a unit 3-vector homogeneously randomised over 4pi
35 // solid angle. It can be used in any particle 36 // solid angle. It can be used in any particle scattering methods
36 // instead of: 37 // instead of:
37 // z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQR 38 // z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQRT(1-R1*R1)*COS(2*pi*R2)
38 // providing more performant results. 39 // providing more performant results.
39 40
40 // History: 41 // History:
41 // 19.10.17 E. Tcherniaev, use of G.Marsagl <<
42 // 06.04.17 E. Tcherniaev, added G4RandomDi <<
43 // 15.03.16 E. Tcherniaev, removed unnecess 42 // 15.03.16 E. Tcherniaev, removed unnecessary if and unit()
44 // 18.03.08 V. Grichine, unit radius sphere 43 // 18.03.08 V. Grichine, unit radius sphere surface based algorithm
45 // ~ 2007 M. Kossov, algorithm based on 8 44 // ~ 2007 M. Kossov, algorithm based on 8 Quadrants technique
46 // 45 //
47 // ------------------------------------------- 46 // ------------------------------------------------------------
48 #ifndef G4RANDOMDIR_HH 47 #ifndef G4RANDOMDIR_HH
49 #define G4RANDOMDIR_HH 48 #define G4RANDOMDIR_HH
50 49
51 #include <CLHEP/Units/PhysicalConstants.h> 50 #include <CLHEP/Units/PhysicalConstants.h>
52 51
53 #include "G4ThreeVector.hh" <<
54 #include "Randomize.hh" <<
55 #include "globals.hh" 52 #include "globals.hh"
>> 53 #include "Randomize.hh"
>> 54 #include "G4ThreeVector.hh"
56 55
57 // G.Marsaglia (1972) method <<
58 inline G4ThreeVector G4RandomDirection() 56 inline G4ThreeVector G4RandomDirection()
59 { 57 {
60 G4double u, v, b; << 58 G4double z = 2.*G4UniformRand() - 1.; // z = cos(theta)
61 do << 59 G4double rho = std::sqrt((1.+z)*(1.-z)); // rho = sqrt(1-z*z)
62 { << 60 G4double phi = CLHEP::twopi*G4UniformRand();
63 u = 2. * G4UniformRand() - 1.; << 61 return G4ThreeVector(rho*std::cos(phi), rho*std::sin(phi), z);
64 v = 2. * G4UniformRand() - 1.; <<
65 b = u * u + v * v; <<
66 } while(b > 1.); <<
67 G4double a = 2. * std::sqrt(1. - b); <<
68 return G4ThreeVector(a * u, a * v, 2. * b - <<
69 } <<
70 <<
71 inline G4ThreeVector G4RandomDirection(G4doubl <<
72 { <<
73 G4double z = (1. - cosTheta) * G4UniformRa <<
74 G4double rho = std::sqrt((1. + z) * (1. - z) <<
75 G4double phi = CLHEP::twopi * G4UniformRand( <<
76 return G4ThreeVector(rho * std::cos(phi), rh <<
77 } 62 }
78 63
79 #endif /* G4RANDOMDIR_HH */ << 64 #endif /* G4RANDOMDIR_HH */
80 65