CalcCurvatureSignum.h

/**************************************************************************
 * basf2 (Belle II Analysis Software Framework)                           *
 * Author: The Belle II Collaboration                                     *
 *                                                                        *
 * See git log for contributors and copyright holders.                    *
 * This file is licensed under LGPL-3.0, see LICENSE.md.                  *
 **************************************************************************/
 
#pragma once
#include <framework/geometry/B2Vector3.h>
 
 
namespace Belle2 {
  inline short calcCurvatureSignum(std::vector<SpacePoint const*> const& measurements)
  {
    if (measurements.size() < 3) return 0;
    float sumOfCurvature = 0.;
    for (unsigned int i = 0; i < measurements.size() - 2; ++i) {
      B2Vector3D ab = measurements.at(i + 1)->getPosition() - measurements.at(i)->getPosition();
      ab.SetZ(0.);
      B2Vector3D bc = measurements.at(i + 2)->getPosition() - measurements.at(i + 1)->getPosition();
      bc.SetZ(0.);
      sumOfCurvature += bc.Orthogonal() * ab; //normal vector of m_vecBC times segment of ba
    }
    // signum
    return (0 < sumOfCurvature) - (sumOfCurvature < 0);
  }

}