TrackUtils.cxx

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// our header
#include "lardata/ArtDataHelper/TrackUtils.h"

// LArSoft libraries
#include "larcore/CoreUtils/ServiceUtil.h"
#include "larcore/Geometry/Geometry.h"
#include "larcore/Geometry/WireReadout.h"
#include "larcorealg/CoreUtils/RealComparisons.h"
#include "larcorealg/Geometry/GeometryCore.h"
#include "larcorealg/Geometry/PlaneGeo.h"
#include "larcorealg/Geometry/TPCGeo.h"
#include "larcoreobj/SimpleTypesAndConstants/PhysicalConstants.h" // util::pi()
#include "larcoreobj/SimpleTypesAndConstants/geo_vectors.h"       // geo::Vector_t
#include "lardataobj/RecoBase/Track.h"

// framework libraries
#include "cetlib_except/exception.h"

// ROOT libraries

// C/C++ standard libraries
#include <cmath>

//------------------------------------------------------------------------------
double lar::util::TrackProjectedLength(recob::Track const& track, geo::View_t view)
{

  if (view == geo::kUnknown) {
    throw cet::exception("TrackProjectedLength") << "cannot provide projected length for "
                                                 << "unknown view\n";
  }
  double length = 0.;

  auto const& wireReadoutGeom = art::ServiceHandle<geo::WireReadout>()->Get();
  double angleToVert = 0.;
  for (auto const& plane : wireReadoutGeom.Iterate<geo::PlaneGeo>(geo::CryostatID{0})) {
    if (plane.View() == view) {
      angleToVert = plane.Wire(0).ThetaZ(false) - 0.5 * ::util::pi<>();
      break;
    }
  }

  // now loop over all points in the trajectory and add the contribution to the
  // to the desired view

  for (size_t p = 1; p < track.NumberTrajectoryPoints(); ++p) {
    const auto& pos_cur = track.LocationAtPoint(p);
    const auto& pos_prev = track.LocationAtPoint(p - 1);
    double dist =
      std::sqrt(std::pow(pos_cur.x() - pos_prev.x(), 2) + std::pow(pos_cur.y() - pos_prev.y(), 2) +
                std::pow(pos_cur.z() - pos_prev.z(), 2));

    // (sin(angleToVert),cos(angleToVert)) is the direction perpendicular to wire
    // fDir[p-1] is the direction between the two relevant points
    const auto& dir_prev = track.DirectionAtPoint(p - 1);
    double cosgamma =
      std::abs(std::sin(angleToVert) * dir_prev.Y() + std::cos(angleToVert) * dir_prev.Z());

    length += dist / cosgamma;
  } // end loop over distances between trajectory points

  return length;
} // lar::util::TrackProjectedLength()

//------------------------------------------------------------------------------
double lar::util::TrackPitchInView(recob::Track const& track,
                                   geo::View_t view,
                                   size_t trajectory_point /* = 0 */)
{
  /*
    * The plan:
    * 1. find the wire plane we are talking about
    *    (in the right TPC and with the right view)
    * 2. ask the plane the answer
    *
    */

  if (trajectory_point >= track.NumberTrajectoryPoints()) {
    cet::exception("TrackPitchInView")
      << "ERROR: Asking for trajectory point #" << trajectory_point
      << " when trajectory vector size is of size " << track.NumberTrajectoryPoints() << ".\n";
  }
  recob::Track::TrajectoryPoint_t const& point = track.TrajectoryPoint(trajectory_point);

  // this throws if the position is not in any TPC,
  // or if there is no view with specified plane
  auto const& geom = *(lar::providerFrom<geo::Geometry>());
  auto const& wireReadoutGeom = art::ServiceHandle<geo::WireReadout>()->Get();
  geo::PlaneGeo const& plane = wireReadoutGeom.Plane(geom.PositionToTPCID(point.position), view);

  //
  // 2. project the direction of the track on that plane
  //
  // this is the projection of the direction of the track on the wire plane;
  // it is 2D and its second component ("Y()") is on wire coordinate direction;
  // remember that the projection modulus is smaller than 1 because it is
  // the 3D direction versor, deprived of its drift direction component
  auto const& proj = plane.Projection(point.direction());

  if (lar::util::RealComparisons(1e-4).zero(proj.Y())) {
    throw cet::exception("Track") << "track at point #" << trajectory_point
                                  << " is almost parallel to the wires in view "
                                  << geo::PlaneGeo::ViewName(view) << " (wire direction is "
                                  << plane.GetWireDirection() << "; track direction is "
                                  << point.direction() << ", its projection on plane " << plane.ID()
                                  << " is " << proj << ").\n";
  }

  //
  // 3. scale that projection so that it covers a wire pitch worth in the wire
  //    coordinate direction;
  //    WirePitch() is what gives this vector a physical size [cm]
  //
  return proj.R() / std::abs(proj.Y()) * plane.WirePitch();

} // lar::util::TrackPitchInView()

//------------------------------------------------------------------------------