LineIntersection2D.h

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/*
  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
*/
 
// LineIntersection2D.h, (c) ATLAS Detector software
 
#ifndef TRKEXUTILS_LINEINTERSECTION2D_H
#define TRKEXUTILS_LINEINTERSECTION2D_H
 
#include <cmath>
#include <utility>
 
#ifndef NUMERICALSTABLE
#define NUMERICALSTABLE 10e-7
#endif
 
namespace Trk {
 
/* @struct LineIntersction2D
 
  Helper method having 2 lines given with two sets of points each
 
  (x1,y1)(x2,y2) - line a
  (X1,Y1)(X2,Y2) - line b
 
  @author Andreas.Salzburger@cern.ch
 */
 
struct LineIntersection2D
{
 
  bool valid;
  double interX;
  double interY;
  double k, K, d, D;
 
  LineIntersection2D(double x1,
                     double y1,
                     double x2,
                     double y2,
                     double X1,
                     double Y1,
                     double X2,
                     double Y2)
  {
    // diffs, k's and d's
    double deltax = x2 - x1;
    double deltay = y2 - y1;
    double deltaX = X2 - X1;
    double deltaY = Y2 - Y1;
    k = deltay / deltax;
    K = deltaY / deltaX;
    d = y2 - k * x2;
    D = Y2 - K * X2;
    // check if valid
    valid = ((k - K) * (k - K) > NUMERICALSTABLE);
    if (valid) {
      interX = (D - d) / (k - K);
      interY = interX * k + d;
    } else {
      interX = -99999.;
      interY = -99999.;
    }
  }
};
 
} // end of namespace
 
#endif