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//
// $Id:
// GEANT4 tag $Name: geant4-09-03 $
//
// %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//
// MODULE:              G4TessellatedGeometryAlgorithms.hh
//
// Date:                07/08/2005
// Author:              Rickard Holmberg & Pete Truscott
// Organisation:        QinetiQ Ltd, UK (PT)
// Customer:            ESA-ESTEC / TEC-EES
// Contract:            
//
// %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//
// CHANGE HISTORY
// --------------
//
// 07 August 2007, P R Truscott, QinetiQ Ltd, UK - Created, with member
//                 functions based on the work of Rickard Holmberg.
//
// %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
//
// Class description:
//
//   The G4TessellatedGeometryAlgorithms class is used to contain standard
//   routines to determine whether (and if so where) simple geometric shapes
//   intersect.
//   
//   The constructor doesn't need to do anything, and neither does the
//   destructor.
//   
//   IntersectLineAndTriangle2D
//     Determines whether there is an intersection between a line defined
//     by r = p + s.v and a triangle defined by verticies P0, P0+E0 and P0+E1.
//     Here:
//        p = 2D vector
//        s = scaler on [0,infinity)
//        v = 2D vector
//        P0, E0 and E1 are 2D vectors
//     Information about where the intersection occurs is returned in the
//     variable location.
//
//   IntersectLineAndLineSegment2D
//     Determines whether there is an intersection between a line defined
//     by r = P0 + s.D0 and a line-segment with endpoints P1 and P1+D1.
//     Here:
//        P0 = 2D vector
//        s  = scaler on [0,infinity)
//        D0 = 2D vector
//        P1 and D1 are 2D vectors
//     Information about where the intersection occurs is returned in the
//     variable location.

///////////////////////////////////////////////////////////////////////////////
#ifndef G4TessellatedGeometryAlgorithms_hh
#define G4TessellatedGeometryAlgorithms_hh 1

#include "globals.hh"
#include "G4TwoVector.hh"

class G4TessellatedGeometryAlgorithms
{
  public:  // with description

    static G4TessellatedGeometryAlgorithms* GetInstance();
    G4bool IntersectLineAndTriangle2D (const G4TwoVector p,
                                       const G4TwoVector v,
                                       const G4TwoVector P0, 
                                       const G4TwoVector E0,
                                       const G4TwoVector E1,
                                             G4TwoVector location[2]);

    G4int IntersectLineAndLineSegment2D (const G4TwoVector P0,
                                         const G4TwoVector D0,
                                         const G4TwoVector P1,
                                         const G4TwoVector D1,
                                               G4TwoVector location[2]);

    inline G4double cross(const G4TwoVector v1, const G4TwoVector v2) const;

  protected:

    G4TessellatedGeometryAlgorithms();

  private:

    static G4TessellatedGeometryAlgorithms *fInstance;
};

#include "G4TessellatedGeometryAlgorithms.icc"

#endif
