Gabriele Cosmo
85 lines
3.1 KiB
C++
85 lines
3.1 KiB
C++
//
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// ********************************************************************
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// * DISCLAIMER *
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// * *
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// * The following disclaimer summarizes all the specific disclaimers *
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// * of contributors to this software. The specific disclaimers,which *
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// * govern, are listed with their locations in: *
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// * http://cern.ch/geant4/license *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. *
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// * *
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// * This code implementation is the intellectual property of the *
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// * GEANT4 collaboration. *
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// * By copying, distributing or modifying the Program (or any work *
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// * based on the Program) you indicate your acceptance of this *
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// * statement, and all its terms. *
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// ********************************************************************
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//
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//
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// $Id: G4RandomDirection.hh,v 1.2 2004/11/12 17:38:34 gcosmo Exp $
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// GEANT4 tag $Name: geant4-07-01 $
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//
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//
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// ------------------------------------------------------------
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// GEANT 4 class header file
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// ------------------------------------------------------------
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// Class description:
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//
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// Funtion returning a unit 3-vector homogeneously randomised over 4pi
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// solid angle. It can be used in any particle scattering methods
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// instead of:
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// z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQRT(1-R1*R1)*COS(2*pi*R2)
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// providing more performant results.
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// ------------------------------------------------------------
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#ifndef G4RANDOMDIR_HH
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#define G4RANDOMDIR_HH
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#include "globals.hh"
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#include "Randomize.hh"
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#include "G4ThreeVector.hh"
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inline G4ThreeVector G4RandomDirection()
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{
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// Randomization in one of 8 Quadrants (x>0, y>0, z>0)
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//
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G4double x=G4UniformRand(), y=G4UniformRand(), z=G4UniformRand();
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G4double r2= x*x+y*y+z*z;
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while(r2>1.||r2<.000001)
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{
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x = G4UniformRand(); y = G4UniformRand(); z = G4UniformRand();
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r2=x*x+y*y+z*z;
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}
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G4double r=std::sqrt(r2), quad=G4UniformRand();
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if(quad>0.5)
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{
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if(quad>0.75)
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{
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if(quad>0.875) return G4ThreeVector(-x/r,-y/r,-z/r);
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else return G4ThreeVector(-x/r,-y/r, z/r);
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}
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else
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{
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if(quad>0.625) return G4ThreeVector(-x/r, y/r,-z/r);
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else return G4ThreeVector(-x/r, y/r, z/r);
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}
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}
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else
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{
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if(quad>0.25)
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{
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if(quad>0.375) return G4ThreeVector( x/r,-y/r,-z/r);
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else return G4ThreeVector( x/r,-y/r, z/r);
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}
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else if(quad>0.125) return G4ThreeVector( x/r, y/r,-z/r);
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}
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return G4ThreeVector( x/r, y/r, z/r);
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}
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#endif /* G4RANDOMDIR_HH */
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