TRT_OverlapDescriptor.cxx

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/*
  Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
*/

// TRT_OverlapDescriptor.cxx, (c) ATLAS Detector software
 
// InDet
#include "InDetTrackingGeometry/TRT_OverlapDescriptor.h"
#include "TRT_ReadoutGeometry/TRT_BaseElement.h"
// Trk
#include "TrkSurfaces/Surface.h"
#include "TrkSurfaces/SurfaceBounds.h"

bool
InDet::TRT_OverlapDescriptor::reachableSurfaces(
  std::vector<Trk::SurfaceIntersection>& cSurfaces,
  const Trk::Surface& tsf,
  const Amg::Vector3D& position,
  const Amg::Vector3D& momentum) const
 
{
  const Amg::Vector3D dir = momentum.unit();
  // first add the target surface - if it fits
  int nextInt = checkAndFill(cSurfaces, tsf, position, dir);
  if (!nextInt)
    return true;
 
  // make sure we have the correct associated element
  const auto* tmp = tsf.associatedDetectorElement();
  const InDetDD::TRT_BaseElement* trtBaseElement =
    tmp->detectorType() == Trk::DetectorElemType::TRT
      ? static_cast<const InDetDD::TRT_BaseElement*>(tmp)
      : nullptr;
 
  // we have a trt base element
  if (trtBaseElement) {
 
    Identifier strawID = tsf.associatedDetectorElementIdentifier();
 
    // straw Max
    int strawMax = trtBaseElement->nStraws() - 1;
    int strawInt = m_trtIdHelper->straw(strawID);
 
    if (strawInt != 0 && strawInt < strawMax && strawMax != -999) {
      // get the next straw
      Identifier nextID =
        m_trtIdHelper->straw_id(trtBaseElement->identify(), strawInt + nextInt);
      const Trk::Surface* nextStraw = (strawInt > 1 && strawInt < strawMax)
                                        ? (&(trtBaseElement->surface(nextID)))
                                        : nullptr;
      if (nextStraw)
        nextInt = checkAndFill(cSurfaces, *nextStraw, position, dir);
    }
  }
 
  return true;
}
 
int
InDet::TRT_OverlapDescriptor::checkAndFill(
  std::vector<Trk::SurfaceIntersection>& cSurfaces,
  const Trk::Surface& sf,
  const Amg::Vector3D& pos,
  const Amg::Vector3D& dir) const
{
  Trk::Intersection sfIntersection =
    sf.straightLineIntersection(pos, dir, false, false);
  // we have a valid intersection - is it within tolerance ?
  if (sfIntersection.valid) {
    // this is the boundary cylinder of the straw surface
    double rSurface2 = sf.bounds().r() * sf.bounds().r();
    // what's the distance - hess' normal form
    const Amg::Vector3D& sCenter = sf.center();
    const Amg::Vector3D sDirection = sf.transform().rotation().col(2);
    // d^2 = | (dir) x
    double d2 =
      (sDirection.cross((sfIntersection.position - sCenter))).squaredNorm();
    // check it
    bool acceptSurface =
      d2 < (m_outsideTolerance * m_outsideTolerance * rSurface2);
    if (acceptSurface)
      cSurfaces.emplace_back(sfIntersection, &sf);
    // give the break signal if it's really inside
    return (d2 < (m_breakTolerance * m_breakTolerance * rSurface2)
              ? 0
              : (sfIntersection.position.phi() > sf.center().phi() ? 1 : -1));
  }
  // base the decision on the position phi value
  return (pos.phi() > sf.center().phi() ? 1 : -1);
}