| 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 1.5 2008/03/19 17:00:20 gcosmo Exp $ |
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| 28 | // GEANT4 tag $Name: HEAD $ |
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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 | // Function 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 | // History: |
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| 43 | // 18.03.08 V. Grichine, unit radius sphere surface based algorithm |
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| 44 | // ~ 2007 M. Kossov, algorithm based on 8 Quadrants technique |
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| 45 | // |
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| 46 | // ------------------------------------------------------------ |
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| 47 | #ifndef G4RANDOMDIR_HH |
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| 48 | #define G4RANDOMDIR_HH |
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| 49 | |
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| 50 | #include "globals.hh" |
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| 51 | #include "Randomize.hh" |
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| 52 | #include "G4ThreeVector.hh" |
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| 53 | |
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| 54 | inline G4ThreeVector G4RandomDirection() |
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| 55 | { |
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| 56 | G4double cosTheta = 2.*G4UniformRand()-1.; |
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| 57 | G4double sinTheta2 = 1. - cosTheta*cosTheta; |
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| 58 | if( sinTheta2 < 0.) sinTheta2 = 0.; |
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| 59 | G4double sinTheta = std::sqrt(sinTheta2); |
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| 60 | G4double phi = twopi*G4UniformRand(); |
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| 61 | return G4ThreeVector(sinTheta*std::cos(phi), |
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| 62 | sinTheta*std::sin(phi), cosTheta).unit(); |
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| 63 | } |
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| 64 | |
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| 65 | #endif /* G4RANDOMDIR_HH */ |
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