AthenaTrackingAction.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "AthenaTrackingAction.h"
 
#include <iostream>
 
#include "G4Event.hh"
#include "G4EventManager.hh"
 
#include "MCTruth/AtlasG4EventUserInfo.h"
#include "MCTruth/PrimaryParticleInformation.h"
#include "MCTruth/TrackHelper.h"
#include "MCTruth/TrackInformation.h"
#include "MCTruthBase/AtlasTrajectory.h"
 
namespace G4UA
{
 
  //---------------------------------------------------------------------------
  // Constructor
  //---------------------------------------------------------------------------
  AthenaTrackingAction::AthenaTrackingAction(MSG::Level lvl,
                                             int secondarySavingLevel, int subDetVolLevel)
    : AthMessaging("AthenaTrackingAction")
    , m_secondarySavingLevel(secondarySavingLevel)
    , m_subDetVolLevel(subDetVolLevel)
  {
    setLevel(lvl);
  }
 
  //---------------------------------------------------------------------------
  // Pre-tracking action.
  //---------------------------------------------------------------------------
  void AthenaTrackingAction::PreUserTrackingAction(const G4Track* track)
  {
    ATH_MSG_DEBUG("Starting to track a new particle");
 
    // Use the TrackHelper code to identify the kind of particle.
    TrackHelper trackHelper(track);
 
    // Condition for storing the GenParticle in the AtlasG4EventUserInfo for later.
    if (trackHelper.IsPrimary() || trackHelper.IsRegisteredSecondary())
    {
      HepMC::GenParticlePtr currentGenParticle = trackHelper.GetTrackInformation()->GetCurrentGenParticle();
 
      // Assign the GenParticle to the AtlasG4EventUserInfo.
      AtlasG4EventUserInfo* atlasG4EvtUserInfo = static_cast<AtlasG4EventUserInfo*>
        (G4EventManager::GetEventManager()->GetConstCurrentEvent()->GetUserInformation());
      if (trackHelper.IsPrimary()) atlasG4EvtUserInfo->SetCurrentPrimaryGenParticle(currentGenParticle);
      atlasG4EvtUserInfo->SetCurrentGenParticle(std::move(currentGenParticle));
    }
 
    // Condition for creating a trajectory object to store truth.
    if (trackHelper.IsPrimary() ||
        (trackHelper.IsRegisteredSecondary() && m_secondarySavingLevel>1) ||
        (trackHelper.IsSecondary() && m_secondarySavingLevel>2))
    {
      ATH_MSG_DEBUG("Preparing an AtlasTrajectory for saving truth");
 
      // Create a new AtlasTrajectory for this particle
      AtlasTrajectory* trajectory = new AtlasTrajectory(track, m_subDetVolLevel);
 
      // Assign the trajectory to the tracking manager.
      // TODO: consider caching the tracking manager once to reduce overhead.
      auto trkMgr = G4EventManager::GetEventManager()->GetTrackingManager();
      //trajectory->setTrackingManager(trkMgr);
      trkMgr->SetStoreTrajectory(true);
      trkMgr->SetTrajectory(trajectory);
    }
  }
 
  //---------------------------------------------------------------------------
  // Post-tracking action.
  //---------------------------------------------------------------------------
  void AthenaTrackingAction::PostUserTrackingAction(const G4Track* /*track*/)
  {
    ATH_MSG_DEBUG("Finished tracking a particle");
 
    // We are done tracking this particle, so reset the trajectory.
    // TODO: consider caching the tracking manager once to reduce overhead.
    G4EventManager::GetEventManager()->GetTrackingManager()->
      SetStoreTrajectory(false);
  }
 
} // namespace G4UA