| [833] | 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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