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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 *
6 // * the Geant4 Collaboration. It is provided 6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License 7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/ 8 // * LICENSE and available at http://cern.ch/geant4/license . These *
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 *
22 // * use in resulting scientific publicati 22 // * use in resulting scientific publications, and indicate your *
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24 // ******************************************* 24 // ********************************************************************
25 // 25 //
26 // 26 //
>> 27 // $Id: G4RandomDirection.hh,v 1.5 2008-03-19 17:00:20 gcosmo Exp $
>> 28 // GEANT4 tag $Name: geant4-09-04-patch-02 $
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 // Function 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 41
40 // History: 42 // 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 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> <<
52 <<
53 #include "G4ThreeVector.hh" <<
54 #include "Randomize.hh" <<
55 #include "globals.hh" 50 #include "globals.hh"
>> 51 #include "Randomize.hh"
>> 52 #include "G4ThreeVector.hh"
56 53
57 // G.Marsaglia (1972) method <<
58 inline G4ThreeVector G4RandomDirection() 54 inline G4ThreeVector G4RandomDirection()
59 { 55 {
60 G4double u, v, b; << 56 G4double cosTheta = 2.*G4UniformRand()-1.;
61 do << 57 G4double sinTheta2 = 1. - cosTheta*cosTheta;
62 { << 58 if( sinTheta2 < 0.) sinTheta2 = 0.;
63 u = 2. * G4UniformRand() - 1.; << 59 G4double sinTheta = std::sqrt(sinTheta2);
64 v = 2. * G4UniformRand() - 1.; << 60 G4double phi = twopi*G4UniformRand();
65 b = u * u + v * v; << 61 return G4ThreeVector(sinTheta*std::cos(phi),
66 } while(b > 1.); << 62 sinTheta*std::sin(phi), cosTheta).unit();
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 } 63 }
78 64
79 #endif /* G4RANDOMDIR_HH */ << 65 #endif /* G4RANDOMDIR_HH */
80 66