include/Geant4/G4INCLIntersection.hh

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0025 //
0026 // INCL++ intra-nuclear cascade model
0027 // Alain Boudard, CEA-Saclay, France
0028 // Joseph Cugnon, University of Liege, Belgium
0029 // Jean-Christophe David, CEA-Saclay, France
0030 // Pekka Kaitaniemi, CEA-Saclay, France, and Helsinki Institute of Physics, Finland
0031 // Sylvie Leray, CEA-Saclay, France
0032 // Davide Mancusi, CEA-Saclay, France
0033 //
0034 #define INCLXX_IN_GEANT4_MODE 1
0035
0036 #include "globals.hh"
0037
0038 /** \file G4INCLIntersection.hh
0039  * \brief Simple class for computing intersections between a straight line and a sphere.
0040  *
0041  * \date 12 December 2011
0042  * \author Davide Mancusi
0043  */
0044
0045 #ifndef G4INCLINTERSECTION_HH
0046 #define G4INCLINTERSECTION_HH 1
0047
0048 #include "G4INCLThreeVector.hh"
0049 #include <utility>
0050
0051 namespace G4INCL {
0052
0053   /** \brief Intersection-point structure
0054    *
0055    * The structure contains the time and position of the intersection point
0056    * of a trajectory with a surface, if it exists.
0057    */
0058   struct Intersection {
0059     Intersection(const G4bool e, const G4double t, const ThreeVector &p) :
0060       exists(e), time(t), position(p) {}
0061     G4bool exists;
0062     G4double time;
0063     ThreeVector position;
0064   };
0065
0066   namespace IntersectionFactory {
0067
0068     /** \brief Compute the first intersection of a straight particle
0069      *         trajectory with a sphere.
0070      *
0071      * \param x0 the starting position of the trajectory
0072      * \param p the trajectory direction
0073      * \param r the radius of the sphere (centred in the origin)
0074      * \return an Intersection. The G4bool is true if an intersection exists,
0075      *         in which case its position is stored in the ThreeVector and
0076      *         its time in the G4double.
0077      */
0078     Intersection getEarlierTrajectoryIntersection(const ThreeVector &x0, const ThreeVector &p, const G4double r);
0079     /** \brief Compute the second intersection of a straight particle
0080      *         trajectory with a sphere.
0081      *
0082      * \param x0 the starting position of the trajectory
0083      * \param p the trajectory direction
0084      * \param r the radius of the sphere (centred in the origin)
0085      * \return an Intersection. The G4bool is true if an intersection exists,
0086      *         in which case its position is stored in the ThreeVector and
0087      *         its time in the G4double.
0088      */
0089     Intersection getLaterTrajectoryIntersection(const ThreeVector &x0, const ThreeVector &p, const G4double r);
0090     /** \brief Compute both intersections of a straight particle
0091      *         trajectory with a sphere.
0092      *
0093      * \param x0 the starting position of the trajectory
0094      * \param p the trajectory direction
0095      * \param r the radius of the sphere (centred in the origin)
0096      * \return an Intersection. The G4bool is true if an intersection exists,
0097      *         in which case its position is stored in the ThreeVector and
0098      *         its time in the G4double.
0099      */
0100     std::pair<Intersection,Intersection> getTrajectoryIntersections(const ThreeVector &x0, const ThreeVector &p, const G4double r);
0101
0102     namespace {
0103
0104       Intersection getTrajectoryIntersection(const ThreeVector &x0, const ThreeVector &v, const G4double r, const G4bool earliest) {
0105         const G4double scalarVelocity = v.mag();
0106         ThreeVector velocityUnitVector = v / scalarVelocity;
0107
0108         ThreeVector positionTransverse = x0 - velocityUnitVector * x0.dot(velocityUnitVector);
0109         const G4double impactParameter = positionTransverse.mag();
0110
0111         const G4double r2 = r*r;
0112         G4double distanceZ2 = r2 - impactParameter * impactParameter;
0113         if(distanceZ2 < 0.0)
0114           return Intersection(false, 0.0, ThreeVector());
0115
0116         const G4double distanceZ = std::sqrt(distanceZ2);
0117         const ThreeVector position = positionTransverse + velocityUnitVector * (earliest ? -distanceZ : distanceZ);
0118         const G4double time = (position-x0).dot(velocityUnitVector)/scalarVelocity;
0119         return Intersection(true, time, position);
0120       }
0121
0122     }
0123
0124     inline Intersection getEarlierTrajectoryIntersection(const ThreeVector &x0, const ThreeVector &p, const G4double r) {
0125       return getTrajectoryIntersection(x0, p, r, true);
0126     }
0127
0128     inline Intersection getLaterTrajectoryIntersection(const ThreeVector &x0, const ThreeVector &p, const G4double r) {
0129       return getTrajectoryIntersection(x0, p, r, false);
0130     }
0131
0132     inline std::pair<Intersection,Intersection> getTrajectoryIntersections(const ThreeVector &x0, const ThreeVector &p, const G4double r) {
0133       return std::make_pair(
0134                             getTrajectoryIntersection(x0, p, r, true),
0135                             getTrajectoryIntersection(x0, p, r, false)
0136                            );
0137     }
0138   }
0139
0140 }
0141
0142 #endif /* G4INCLINTERSECTION_HH */