GlobalFieldManagerTool.cxx

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/*
  Copyright (C) 2002-2020 CERN for the benefit of the ATLAS collaboration
*/
 
// Main header
#include "G4AtlasTools/GlobalFieldManagerTool.h"
 
// Local package include
#include "TightMuonSteppingFieldManager.h"
 
// Geant4 includes
#include "G4ChordFinder.hh"
#include "G4FieldManager.hh"
#include "G4MagIntegratorStepper.hh"
#include "G4MagneticField.hh"
#include "G4PropagatorInField.hh"
#include "G4TransportationManager.hh"
#include "G4Version.hh"
#include "G4VIntegrationDriver.hh"
 
//-----------------------------------------------------------------------------
// Tool constructor
//-----------------------------------------------------------------------------
GlobalFieldManagerTool::GlobalFieldManagerTool(const std::string& type,
                                               const std::string& name,
                                               const IInterface* parent)
  : G4FieldManagerToolBase(type, name, parent)
{
}
 
//-----------------------------------------------------------------------------
// Initialize a field manager
//-----------------------------------------------------------------------------
StatusCode GlobalFieldManagerTool::initializeField()
{
  ATH_MSG_DEBUG("initializeField");
 
  if (m_fieldOn) {
 
    // Retrieve the G4MagneticField
    G4MagneticField* field = m_fieldSvc->getField();
 
    // Retrieve the global field manager
    auto transpManager = G4TransportationManager::GetTransportationManager();
 
    auto* field_manager = [&] () -> G4FieldManager* {
      if (m_useTightMuonStepping){
        // In the case of tight stepping we need to make our own global field manager
        // Create a new field manager
        auto* stepping_field_manager = new TightMuonSteppingFieldManager();
 
        // Assign it to the global field manager
        transpManager->SetFieldManager(stepping_field_manager);
        return stepping_field_manager;
      } else {
        // Otherwise get the default from the transportation manager
        return transpManager->GetFieldManager();
      }
    }();
 
    // Configure the field manager
    field_manager->SetDetectorField(field);
    ATH_CHECK( setFieldParameters(field_manager) );
 
    // Create and configure the ChordFinder
    field_manager->CreateChordFinder(field);
 
#if G4VERSION_NUMBER < 1040
    ATH_MSG_DEBUG("Old style stepper setting");
    G4MagIntegratorStepper* stepper = getStepper(m_integratorStepper, field);
    G4MagInt_Driver* magDriver = field_manager->GetChordFinder()->GetIntegrationDriver();
    magDriver->RenewStepperAndAdjust(stepper);
#else
    ATH_MSG_DEBUG("New style stepper setting");
    G4VIntegrationDriver* driver = createDriverAndStepper(m_integratorStepper, field);
    G4ChordFinder* chordFinder = field_manager->GetChordFinder();
    chordFinder->SetIntegrationDriver(driver);
#endif
 
    // Configure the propagator
    G4PropagatorInField* propagator = transpManager->GetPropagatorInField();
    if (m_maxStep>0) propagator->SetLargestAcceptableStep(m_maxStep);
  }
 
  return StatusCode::SUCCESS;
}