Geant4  10.02.p02
G4RandomDirection.hh
Go to the documentation of this file.
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 //
27 // $Id: G4RandomDirection.hh 97527 2016-06-03 14:59:04Z gcosmo $
28 //
29 //
30 // ------------------------------------------------------------
31 // GEANT 4 class header file
32 // ------------------------------------------------------------
33 // Class description:
34 //
35 // Function returning a unit 3-vector homogeneously randomised over 4pi
36 // solid angle. It can be used in any particle scattering methods
37 // instead of:
38 // z=R1, x=SQRT(1-R1*R1)*SIN(2*pi*R2), y=SQRT(1-R1*R1)*COS(2*pi*R2)
39 // providing more performant results.
40 
41 // History:
42 // 15.03.16 E. Tcherniaev, removed unnecessary if and unit()
43 // 18.03.08 V. Grichine, unit radius sphere surface based algorithm
44 // ~ 2007 M. Kossov, algorithm based on 8 Quadrants technique
45 //
46 // ------------------------------------------------------------
47 #ifndef G4RANDOMDIR_HH
48 #define G4RANDOMDIR_HH
49 
50 #include <CLHEP/Units/PhysicalConstants.h>
51 
52 #include "globals.hh"
53 #include "Randomize.hh"
54 #include "G4ThreeVector.hh"
55 
57 {
58  G4double z = 2.*G4UniformRand() - 1.; // z = cos(theta)
59  G4double rho = std::sqrt((1.+z)*(1.-z)); // rho = sqrt(1-z*z)
61  return G4ThreeVector(rho*std::cos(phi), rho*std::sin(phi), z);
62 }
63 
64 #endif /* G4RANDOMDIR_HH */
CLHEP::Hep3Vector G4ThreeVector
G4double z
Definition: TRTMaterials.hh:39
G4ThreeVector G4RandomDirection()
#define G4UniformRand()
Definition: Randomize.hh:97
static const double twopi
Definition: G4SIunits.hh:75
double G4double
Definition: G4Types.hh:76