Gabriele Cosmo
176 lines
5.6 KiB
C++
176 lines
5.6 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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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. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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//
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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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// Utility functions
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// History:
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//
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// 24.08.17 - E.Tcherniaev, added G4RandomRadiusInRing, G4RandomPointInEllipse
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// G4RandomPointOnEllipse, G4RandomPointOnEllipsoid
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// 07.11.08 - P.Gumplinger, based on implementation in G4OpBoundaryProcess
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//
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// ---------------------------------------------------------------------------
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#ifndef G4RANDOMTOOLS_HH
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#define G4RANDOMTOOLS_HH
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#include <CLHEP/Units/PhysicalConstants.h>
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#include "globals.hh"
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#include "Randomize.hh"
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#include "G4TwoVector.hh"
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#include "G4ThreeVector.hh"
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#include "G4RandomDirection.hh"
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// ---------------------------------------------------------------------------
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// Returns a random lambertian unit vector (rejection sampling)
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//
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inline G4ThreeVector G4LambertianRand(const G4ThreeVector& normal)
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{
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G4ThreeVector vect;
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G4double ndotv;
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G4int count=0;
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const G4int max_trials = 1024;
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do
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{
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++count;
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vect = G4RandomDirection();
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ndotv = normal * vect;
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if (ndotv < 0.0)
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{
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vect = -vect;
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ndotv = -ndotv;
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}
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} while (!(G4UniformRand() < ndotv) && (count < max_trials));
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return vect;
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}
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// ---------------------------------------------------------------------------
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// Chooses a random vector within a plane given by the unit normal
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//
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inline G4ThreeVector G4PlaneVectorRand(const G4ThreeVector& normal)
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{
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G4ThreeVector vec1 = normal.orthogonal();
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G4ThreeVector vec2 = vec1.cross(normal);
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G4double phi = CLHEP::twopi*G4UniformRand();
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G4double cosphi = std::cos(phi);
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G4double sinphi = std::sin(phi);
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return cosphi * vec1 + sinphi * vec2;
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}
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// ---------------------------------------------------------------------------
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// Returns a random radius in annular ring
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//
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inline G4double G4RandomRadiusInRing(G4double rmin, G4double rmax)
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{
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if (rmin == rmax)
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{
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return rmin;
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}
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G4double k = G4UniformRand();
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return (rmin <= 0) ? rmax*std::sqrt(k)
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: std::sqrt(k*rmax*rmax + (1.-k)*rmin*rmin);
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}
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// ---------------------------------------------------------------------------
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// Returns a random point in ellipse (x/a)^2 + (y/b)^2 = 1
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// (rejection sampling)
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//
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inline G4TwoVector G4RandomPointInEllipse(G4double a, G4double b)
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{
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G4double aa = (a*a == 0) ? 0 : 1/(a*a);
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G4double bb = (b*b == 0) ? 0 : 1/(b*b);
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for (G4int i=0; i<1000; ++i)
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{
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G4double x = a*(2*G4UniformRand() - 1);
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G4double y = b*(2*G4UniformRand() - 1);
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if (x*x*aa + y*y*bb <= 1) return G4TwoVector(x,y);
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}
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return G4TwoVector(0,0);
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}
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// ---------------------------------------------------------------------------
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// Returns a random point on ellipse (x/a)^2 + (y/b)^2 = 1
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// (rejection sampling)
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//
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inline G4TwoVector G4RandomPointOnEllipse(G4double a, G4double b)
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{
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G4double A = std::abs(a);
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G4double B = std::abs(b);
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G4double mu_max = std::max(A,B);
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G4double x,y;
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for (G4int i=0; i<1000; ++i)
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{
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G4double phi = CLHEP::twopi*G4UniformRand();
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x = std::cos(phi);
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y = std::sin(phi);
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G4double mu = std::sqrt((B*x)*(B*x) + (A*y)*(A*y));
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if (mu_max*G4UniformRand() <= mu) break;
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}
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return G4TwoVector(A*x,B*y);
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}
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// ---------------------------------------------------------------------------
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// Returns a random point on ellipsoid (x/a)^2 + (y/b)^2 + (z/c)^2 = 1
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// (rejection sampling)
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//
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inline
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G4ThreeVector G4RandomPointOnEllipsoid(G4double a, G4double b, G4double c)
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{
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G4double A = std::abs(a);
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G4double B = std::abs(b);
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G4double C = std::abs(c);
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G4double mu_max = std::max(std::max(A*B,A*C),B*C);
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G4ThreeVector p;
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for (G4int i=0; i<1000; ++i)
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{
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p = G4RandomDirection();
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G4double xbc = p.x()*B*C;
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G4double yac = p.y()*A*C;
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G4double zab = p.z()*A*B;
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G4double mu = std::sqrt(xbc*xbc + yac*yac + zab*zab);
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if (mu_max*G4UniformRand() <= mu) break;
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}
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return G4ThreeVector(A*p.x(),B*p.y(),C*p.z());
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}
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#endif /* G4RANDOMTOOLS_HH */
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