Re-add code, which got lost on last commit.

DDG4/src/Geant4FieldSetup.cpp

+// $Id: Geant4Setup.cpp 578 2013-05-17 22:33:09Z markus.frank $
+//====================================================================
+//  AIDA Detector description implementation for LCD
+//--------------------------------------------------------------------
+//
+//  Author     : M.Frank
+//
+//====================================================================
+// Framework include files
+#include "DD4hep/Handle.h"
+#include "DD4hep/Fields.h"
+#include "DDG4/Factories.h"
+#include "DDG4/Geant4Field.h"
+#include "DDG4/Geant4Converter.h"
+
+#include "G4TransportationManager.hh"
+#include "G4MagIntegratorStepper.hh"
+#include "G4Mag_EqRhs.hh"
+#include "G4ChordFinder.hh"
+#include "G4PropagatorInField.hh"
+
+using namespace std;
+using namespace DD4hep;
+using namespace DD4hep::Simulation;
+typedef DD4hep::Geometry::LCDD lcdd_t;
+
+namespace {
+  struct Geant4FieldSetup;
+  struct Geant4SetupPropertyMap {
+    const map<string,string>& vals;
+    Geant4SetupPropertyMap(const map<string,string>& v) : vals(v) {}
+    string value(const string& key) const;
+    double toDouble(const string& key) const;
+    bool operator[](const string& key) const  { return vals.find(key) != vals.end(); }
+  };
+
+  string Geant4SetupPropertyMap::value(const string& key) const {
+    lcdd_t::PropertyValues::const_iterator iV = vals.find(key);
+    return iV == vals.end() ? "" : (*iV).second;
+  }
+
+  double Geant4SetupPropertyMap::toDouble(const string& key) const {
+    return Geometry::_toDouble(this->value(key));
+  }
+}
+
+static long setup_fields(lcdd_t& lcdd, const Simulation::Geant4Converter& /* cnv */, const map<string,string>& vals) {
+  Geant4SetupPropertyMap pm(vals);
+  DD4hep::Geometry::OverlayedField fld  = lcdd.field();
+  G4MagIntegratorStepper*  stepper = 0;
+  G4MagneticField*         field = 0;
+  G4FieldManager*          fieldMgr = 0;
+  G4TransportationManager* tr = 0;
+  G4PropagatorInField*     propagator = 0;
+  G4ChordFinder*           chordFinder = 0;  
+
+  lcdd_t::PropertyValues::const_iterator iV;
+
+  string eq_typ      = pm.value("equation");
+  string stepper_typ = pm.value("stepper");
+  double value;
+
+  field    = new Simulation::Geant4Field(fld);
+  tr       = G4TransportationManager::GetTransportationManager();
+  fieldMgr = tr->GetFieldManager();
+
+  fieldMgr->SetFieldChangesEnergy(fld.changesEnergy());
+  fieldMgr->SetDetectorField(field);
+
+  G4Mag_EqRhs* equation = ROOT::Reflex::PluginService::Create<G4Mag_EqRhs*>(eq_typ,field);
+  stepper = ROOT::Reflex::PluginService::Create<G4MagIntegratorStepper*>(stepper_typ,equation);
+
+  iV = vals.find("min_chord_step");
+  value = Geometry::_toDouble((iV == vals.end()) ? string("1.0e-2 * mm") : (*iV).second);
+  chordFinder  = new G4ChordFinder(field,value,stepper);
+  propagator   = tr->GetPropagatorInField();
+  fieldMgr->SetChordFinder(chordFinder);
+
+  if ( pm["delta_chord"] ) {
+    chordFinder->SetDeltaChord(pm.toDouble("delta_chord"));
+  }
+  if ( pm["delta_one_step"] ) {
+    fieldMgr->SetAccuraciesWithDeltaOneStep(pm.toDouble("delta_one_step"));
+  }
+  if ( pm["delta_intersection"] ) {
+    fieldMgr->SetDeltaIntersection(pm.toDouble("delta_intersection"));
+  }
+  if ( pm["eps_min"] ) {
+    propagator->SetMinimumEpsilonStep(pm.toDouble("eps_min"));
+  }
+  if ( pm["eps_max"] ) {
+    propagator->SetMaximumEpsilonStep(pm.toDouble("eps_max"));
+  }
+  return 1;
+}
+DECLARE_GEANT4_SETUP(Geant4FieldSetup,setup_fields)