CaloCellSelectorUtils.cxx

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/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
#include "TrackToCalo/CaloCellSelectorUtils.h"
 
#include <algorithm>
#include <cmath>
 
namespace Utils {
    double deltaPhi(double phi1, double phi2) {
        double dPhi = std::fabs(phi1 - phi2);
        if (dPhi > M_PI) dPhi = 2 * M_PI - dPhi;
        return dPhi;
    }
 
    double deltaR2(double eta1, double eta2, double phi1, double phi2) {
        double dPhi = deltaPhi(phi1, phi2);
        double dEta = std::fabs(eta1 - eta2);
        return dEta * dEta + dPhi * dPhi;
    }
 
    double deltaR(double eta1, double eta2, double phi1, double phi2) { return std::sqrt(deltaR2(eta1, eta2, phi1, phi2)); }
 
    void findNearestPoint(const Amg::Vector3D& inputPos, const Trk::CaloExtension* caloExtension, int& nearestIdx,
                          Amg::Vector3D& nearestPos, Amg::Vector3D& nearestMom) {
        const std::vector<Trk::CurvilinearParameters>& intersections = caloExtension->caloLayerIntersections();
        int nPts = intersections.size();
 
        int idxL, idxR, idxMid;
        Amg::Vector3D pos(0, 0, 0), mom(0, 0, 0);  // initialization should be(?) unnecessary, just to suppress scary warning msg...
        Amg::Vector3D posL(0, 0, 0), momL(0, 0, 0);
        Amg::Vector3D posR(0, 0, 0), momR(0, 0, 0);
 
        // find nearest crossing point
        idxL = 0;
        idxR = nPts - 1;
        while ((idxR - idxL) > 1) {
            idxMid = (idxL + idxR) / 2;
            pos = intersections[idxMid].position();
            mom = intersections[idxMid].momentum();
 
            if ((inputPos - pos).dot(mom) > 0) {
                idxL = idxMid;
                std::swap(posL, pos);
                std::swap(momL, mom);
            } else {
                idxR = idxMid;
                std::swap(posR, pos);
                std::swap(momR, mom);
            }
        }
 
        if (idxL == 0) {
            posL = intersections[0].position();
            momL = intersections[0].momentum();
        }
        if (idxR == (nPts - 1)) {
            posR = intersections[nPts - 1].position();
            momR = intersections[nPts - 1].momentum();
        }
 
        float mag2L = (inputPos - posL).mag2();
        float mag2R = (inputPos - posR).mag2();
        nearestIdx = (mag2L < mag2R) ? idxL : idxR;
        nearestPos = (mag2L < mag2R) ? posL : posR;
        nearestMom = (mag2L < mag2R) ? momL : momR;
    }
}  // namespace Utils