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1 // 1 //
2 // ******************************************* 2 // ********************************************************************
3 // * License and Disclaimer << 3 // * DISCLAIMER *
4 // * 4 // * *
5 // * The Geant4 software is copyright of th << 5 // * The following disclaimer summarizes all the specific disclaimers *
6 // * the Geant4 Collaboration. It is provided << 6 // * of contributors to this software. The specific disclaimers,which *
7 // * conditions of the Geant4 Software License << 7 // * govern, are listed with their locations in: *
8 // * LICENSE and available at http://cern.ch/ << 8 // * http://cern.ch/geant4/license *
9 // * include a list of copyright holders. <<
10 // * 9 // * *
11 // * Neither the authors of this software syst 10 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing fin 11 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warran 12 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assum 13 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file << 14 // * use. *
16 // * for the full disclaimer and the limitatio <<
17 // * 15 // * *
18 // * This code implementation is the result << 16 // * This code implementation is the intellectual property of the *
19 // * technical work of the GEANT4 collaboratio << 17 // * GEANT4 collaboration. *
20 // * By using, copying, modifying or distri << 18 // * By copying, distributing or modifying the Program (or any work *
21 // * any work based on the software) you ag << 19 // * based on the Program) you indicate your acceptance of this *
22 // * use in resulting scientific publicati << 20 // * statement, and all its terms. *
23 // * acceptance of all terms of the Geant4 Sof <<
24 // ******************************************* 21 // ********************************************************************
25 // 22 //
26 // 23 //
>> 24 // $Id: G4RandomDirection.hh,v 1.2 2004/11/12 17:38:34 gcosmo Exp $
>> 25 // GEANT4 tag $Name: geant4-07-00-cand-03 $
27 // 26 //
28 // << 27 //
29 // ------------------------------------------- 28 // ------------------------------------------------------------
30 // GEANT 4 class header file << 29 // GEANT 4 class header file
31 // ------------------------------------------- 30 // ------------------------------------------------------------
32 // Class description: 31 // Class description:
33 // 32 //
34 // Function returning a unit 3-vector homogene << 33 // Funtion returning a unit 3-vector homogeneously randomised over 4pi
35 // solid angle. It can be used in any particle 34 // solid angle. It can be used in any particle scattering methods
36 // instead of: 35 // instead of:
37 // z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQR 36 // 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. 37 // 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 // ------------------------------------------- 38 // ------------------------------------------------------------
48 #ifndef G4RANDOMDIR_HH 39 #ifndef G4RANDOMDIR_HH
49 #define G4RANDOMDIR_HH 40 #define G4RANDOMDIR_HH
50 41
51 #include <CLHEP/Units/PhysicalConstants.h> <<
52 <<
53 #include "G4ThreeVector.hh" <<
54 #include "Randomize.hh" <<
55 #include "globals.hh" 42 #include "globals.hh"
>> 43 #include "Randomize.hh"
>> 44 #include "G4ThreeVector.hh"
56 45
57 // G.Marsaglia (1972) method <<
58 inline G4ThreeVector G4RandomDirection() 46 inline G4ThreeVector G4RandomDirection()
59 { 47 {
60 G4double u, v, b; << 48 // Randomization in one of 8 Quadrants (x>0, y>0, z>0)
61 do << 49 //
>> 50 G4double x=G4UniformRand(), y=G4UniformRand(), z=G4UniformRand();
>> 51 G4double r2= x*x+y*y+z*z;
>> 52 while(r2>1.||r2<.000001)
62 { 53 {
63 u = 2. * G4UniformRand() - 1.; << 54 x = G4UniformRand(); y = G4UniformRand(); z = G4UniformRand();
64 v = 2. * G4UniformRand() - 1.; << 55 r2=x*x+y*y+z*z;
65 b = u * u + v * v; << 56 }
66 } while(b > 1.); << 57 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 58
71 inline G4ThreeVector G4RandomDirection(G4doubl << 59 if(quad>0.5)
72 { << 60 {
73 G4double z = (1. - cosTheta) * G4UniformRa << 61 if(quad>0.75)
74 G4double rho = std::sqrt((1. + z) * (1. - z) << 62 {
75 G4double phi = CLHEP::twopi * G4UniformRand( << 63 if(quad>0.875) return G4ThreeVector(-x/r,-y/r,-z/r);
76 return G4ThreeVector(rho * std::cos(phi), rh << 64 else return G4ThreeVector(-x/r,-y/r, z/r);
>> 65 }
>> 66 else
>> 67 {
>> 68 if(quad>0.625) return G4ThreeVector(-x/r, y/r,-z/r);
>> 69 else return G4ThreeVector(-x/r, y/r, z/r);
>> 70 }
>> 71 }
>> 72 else
>> 73 {
>> 74 if(quad>0.25)
>> 75 {
>> 76 if(quad>0.375) return G4ThreeVector( x/r,-y/r,-z/r);
>> 77 else return G4ThreeVector( x/r,-y/r, z/r);
>> 78 }
>> 79 else if(quad>0.125) return G4ThreeVector( x/r, y/r,-z/r);
>> 80 }
>> 81 return G4ThreeVector( x/r, y/r, z/r);
77 } 82 }
78 83
79 #endif /* G4RANDOMDIR_HH */ << 84 #endif /* G4RANDOMDIR_HH */
80 85