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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