1 | // |
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2 | // ******************************************************************** |
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3 | // * License and Disclaimer * |
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4 | // * * |
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5 | // * The Geant4 software is copyright of the Copyright Holders of * |
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6 | // * the Geant4 Collaboration. It is provided under the terms and * |
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7 | // * conditions of the Geant4 Software License, included in the file * |
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8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
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9 | // * include a list of copyright holders. * |
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10 | // * * |
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11 | // * Neither the authors of this software system, nor their employing * |
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12 | // * institutes,nor the agencies providing financial support for this * |
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13 | // * work make any representation or warranty, express or implied, * |
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14 | // * regarding this software system or assume any liability for its * |
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15 | // * use. Please see the license in the file LICENSE and URL above * |
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16 | // * for the full disclaimer and the limitation of liability. * |
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17 | // * * |
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18 | // * This code implementation is the result of the scientific and * |
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19 | // * technical work of the GEANT4 collaboration. * |
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20 | // * By using, copying, modifying or distributing the software (or * |
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21 | // * any work based on the software) you agree to acknowledge its * |
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22 | // * use in resulting scientific publications, and indicate your * |
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23 | // * acceptance of all terms of the Geant4 Software license. * |
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24 | // ******************************************************************** |
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25 | // |
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26 | // |
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27 | // $Id: G4RandomDirection.hh,v 1.3 2006/06/29 19:00:47 gunter Exp $ |
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28 | // GEANT4 tag $Name: geant4-09-01-patch-02 $ |
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29 | // |
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30 | // |
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31 | // ------------------------------------------------------------ |
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32 | // GEANT 4 class header file |
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33 | // ------------------------------------------------------------ |
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34 | // Class description: |
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35 | // |
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36 | // Funtion returning a unit 3-vector homogeneously randomised over 4pi |
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37 | // solid angle. It can be used in any particle scattering methods |
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38 | // instead of: |
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39 | // z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQRT(1-R1*R1)*COS(2*pi*R2) |
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40 | // providing more performant results. |
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41 | // ------------------------------------------------------------ |
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42 | #ifndef G4RANDOMDIR_HH |
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43 | #define G4RANDOMDIR_HH |
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44 | |
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45 | #include "globals.hh" |
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46 | #include "Randomize.hh" |
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47 | #include "G4ThreeVector.hh" |
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48 | |
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49 | inline G4ThreeVector G4RandomDirection() |
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50 | { |
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51 | // Randomization in one of 8 Quadrants (x>0, y>0, z>0) |
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52 | // |
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53 | G4double x=G4UniformRand(), y=G4UniformRand(), z=G4UniformRand(); |
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54 | G4double r2= x*x+y*y+z*z; |
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55 | while(r2>1.||r2<.000001) |
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56 | { |
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57 | x = G4UniformRand(); y = G4UniformRand(); z = G4UniformRand(); |
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58 | r2=x*x+y*y+z*z; |
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59 | } |
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60 | G4double r=std::sqrt(r2), quad=G4UniformRand(); |
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61 | |
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62 | if(quad>0.5) |
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63 | { |
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64 | if(quad>0.75) |
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65 | { |
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66 | if(quad>0.875) return G4ThreeVector(-x/r,-y/r,-z/r); |
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67 | else return G4ThreeVector(-x/r,-y/r, z/r); |
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68 | } |
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69 | else |
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70 | { |
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71 | if(quad>0.625) return G4ThreeVector(-x/r, y/r,-z/r); |
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72 | else return G4ThreeVector(-x/r, y/r, z/r); |
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73 | } |
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74 | } |
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75 | else |
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76 | { |
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77 | if(quad>0.25) |
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78 | { |
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79 | if(quad>0.375) return G4ThreeVector( x/r,-y/r,-z/r); |
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80 | else return G4ThreeVector( x/r,-y/r, z/r); |
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81 | } |
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82 | else if(quad>0.125) return G4ThreeVector( x/r, y/r,-z/r); |
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83 | } |
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84 | return G4ThreeVector( x/r, y/r, z/r); |
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85 | } |
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86 | |
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87 | #endif /* G4RANDOMDIR_HH */ |
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