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//
// G4TessellatedGeometryAlgorithms
//
// 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.

// Author: P.R.Truscott (QinetiQ Ltd, UK), 07.08.2007 - Created, with member
//                            functions based on the work of Rickard Holmberg.
//         M.Gayer (CERN), 12.10.2012 - Reviewed and optimized implementation.
// --------------------------------------------------------------------
#ifndef G4TESSELLATEDGEOMETRYALGORITHMS_HH
#define G4TESSELLATEDGEOMETRYALGORITHMS_HH

#include "G4TwoVector.hh"

/**
 * @brief G4TessellatedGeometryAlgorithms contains standard methods to
 * determine whether (and if so where) simple geometric shapes intersect.
 */

class G4TessellatedGeometryAlgorithms
{
  public:

    /**
     * Determines whether there is an intersection between a line defined
     * by r = p + s.v and a triangle defined by vertices p0, p0+e0 and p0+e1.
     *  @param[in] p Coefficient of line equation.
     *  @param[in] v Coefficient of line equation.
     *  @param[in] p0 First vertex of triangle.
     *  @param[in] e0 Second vertex of triangle.
     *  @param[in] e1 Third vertex of triangle.
     *  @param[out] location The returned location of the intersection.
     *  @returns false if no intersection occours.
     */
    static G4bool IntersectLineAndTriangle2D (const G4TwoVector& p,
                                              const G4TwoVector& v,
                                              const G4TwoVector& p0, 
                                              const G4TwoVector& e0,
                                              const G4TwoVector& e1,
                                                    G4TwoVector location[2]);

    /**
     * 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.
     *  @param[in] p0 Coefficient of line equation.
     *  @param[in] d0 Coefficient of line equation.
     *  @param[in] p1 First line-segment end-point..
     *  @param[in] d1 Delta line-segment end-point.
     *  @param[out] location The returned location of the intersection.
     *  @returns false if no intersection occours.
     */
    static G4int IntersectLineAndLineSegment2D (const G4TwoVector& p0,
                                                const G4TwoVector& d0,
                                                const G4TwoVector& p1,
                                                const G4TwoVector& d1,
                                                      G4TwoVector location[2]);

    /**
     * Ficticious "cross-product" function for two 2D vectors.
     *  @param[in] v1 First 2D vector.
     *  @param[in] v2 Second 2D vector.
     *  @returns The cross-product of v1 and v2.
     */
    static G4double cross(const G4TwoVector& v1, const G4TwoVector& v2);
};

#endif