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1 // 1 //
2 // ******************************************* 2 // ********************************************************************
3 // * License and Disclaimer 3 // * License and Disclaimer *
4 // * 4 // * *
5 // * The Geant4 software is copyright of th 5 // * The Geant4 software is copyright of the Copyright Holders of *
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7 // * conditions of the Geant4 Software License 7 // * conditions of the Geant4 Software License, included in the file *
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9 // * include a list of copyright holders. 9 // * include a list of copyright holders. *
10 // * 10 // * *
11 // * Neither the authors of this software syst 11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing fin 12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warran 13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assum 14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file 15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitatio 16 // * for the full disclaimer and the limitation of liability. *
17 // * 17 // * *
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. *
20 // * By using, copying, modifying or distri 20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you ag 21 // * any work based on the software) you agree to acknowledge its *
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24 // ******************************************* 24 // ********************************************************************
25 // 25 //
26 // 26 //
>> 27 // $Id: G4RandomDirection.hh,v 1.3 2006/06/29 19:00:47 gunter Exp $
>> 28 // GEANT4 tag $Name: geant4-09-00 $
27 // 29 //
28 // << 30 //
29 // ------------------------------------------- 31 // ------------------------------------------------------------
30 // GEANT 4 class header file << 32 // GEANT 4 class header file
31 // ------------------------------------------- 33 // ------------------------------------------------------------
32 // Class description: 34 // Class description:
33 // 35 //
34 // Function returning a unit 3-vector homogene << 36 // Funtion returning a unit 3-vector homogeneously randomised over 4pi
35 // solid angle. It can be used in any particle 37 // solid angle. It can be used in any particle scattering methods
36 // instead of: 38 // instead of:
37 // z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQR 39 // 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. 40 // providing more performant results.
39 <<
40 // 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 <<
44 // 18.03.08 V. Grichine, unit radius sphere <<
45 // ~ 2007 M. Kossov, algorithm based on 8 <<
46 // <<
47 // ------------------------------------------- 41 // ------------------------------------------------------------
48 #ifndef G4RANDOMDIR_HH 42 #ifndef G4RANDOMDIR_HH
49 #define G4RANDOMDIR_HH 43 #define G4RANDOMDIR_HH
50 44
51 #include <CLHEP/Units/PhysicalConstants.h> <<
52 <<
53 #include "G4ThreeVector.hh" <<
54 #include "Randomize.hh" <<
55 #include "globals.hh" 45 #include "globals.hh"
>> 46 #include "Randomize.hh"
>> 47 #include "G4ThreeVector.hh"
56 48
57 // G.Marsaglia (1972) method <<
58 inline G4ThreeVector G4RandomDirection() 49 inline G4ThreeVector G4RandomDirection()
59 { 50 {
60 G4double u, v, b; << 51 // Randomization in one of 8 Quadrants (x>0, y>0, z>0)
61 do << 52 //
>> 53 G4double x=G4UniformRand(), y=G4UniformRand(), z=G4UniformRand();
>> 54 G4double r2= x*x+y*y+z*z;
>> 55 while(r2>1.||r2<.000001)
62 { 56 {
63 u = 2. * G4UniformRand() - 1.; << 57 x = G4UniformRand(); y = G4UniformRand(); z = G4UniformRand();
64 v = 2. * G4UniformRand() - 1.; << 58 r2=x*x+y*y+z*z;
65 b = u * u + v * v; << 59 }
66 } while(b > 1.); << 60 G4double r=std::sqrt(r2), quad=G4UniformRand();
67 G4double a = 2. * std::sqrt(1. - b); <<
68 return G4ThreeVector(a * u, a * v, 2. * b - <<
69 } <<
70 61
71 inline G4ThreeVector G4RandomDirection(G4doubl << 62 if(quad>0.5)
72 { << 63 {
73 G4double z = (1. - cosTheta) * G4UniformRa << 64 if(quad>0.75)
74 G4double rho = std::sqrt((1. + z) * (1. - z) << 65 {
75 G4double phi = CLHEP::twopi * G4UniformRand( << 66 if(quad>0.875) return G4ThreeVector(-x/r,-y/r,-z/r);
76 return G4ThreeVector(rho * std::cos(phi), rh << 67 else return G4ThreeVector(-x/r,-y/r, z/r);
>> 68 }
>> 69 else
>> 70 {
>> 71 if(quad>0.625) return G4ThreeVector(-x/r, y/r,-z/r);
>> 72 else return G4ThreeVector(-x/r, y/r, z/r);
>> 73 }
>> 74 }
>> 75 else
>> 76 {
>> 77 if(quad>0.25)
>> 78 {
>> 79 if(quad>0.375) return G4ThreeVector( x/r,-y/r,-z/r);
>> 80 else return G4ThreeVector( x/r,-y/r, z/r);
>> 81 }
>> 82 else if(quad>0.125) return G4ThreeVector( x/r, y/r,-z/r);
>> 83 }
>> 84 return G4ThreeVector( x/r, y/r, z/r);
77 } 85 }
78 86
79 #endif /* G4RANDOMDIR_HH */ << 87 #endif /* G4RANDOMDIR_HH */
80 88