refactor: Some refactorings around the G4 simulation

Examples/Algorithms/Geant4/include/ActsExamples/Geant4/Geant4Simulation.hpp

@@ -134,10 +134,6 @@ class Geant4Simulation final : public Geant4SimulationBase {
     /// If a physics list has to be instantiated this one is chosen.
     std::string physicsList = "FTFP_BERT";
 
-    std::vector<std::string> volumeMappings;
-
-    std::vector<std::string> materialMappings = {"Silicon"};
-
     std::shared_ptr<const Acts::Volume> killVolume;
     double killAfterTime = std::numeric_limits<double>::infinity();
     bool killSecondaries = false;

Examples/Algorithms/Geant4/src/Geant4Simulation.cpp

@@ -299,7 +299,10 @@ ActsExamples::Geant4Simulation::~Geant4Simulation() = default;
 
 ActsExamples::ProcessCode ActsExamples::Geant4Simulation::execute(
     const ActsExamples::AlgorithmContext& ctx) const {
-  Geant4SimulationBase::execute(ctx);
+  auto ret = Geant4SimulationBase::execute(ctx);
+  if (ret != ProcessCode::SUCCESS) {
+    return ret;
+  }
 
   // Output handling: Simulation
   m_outputParticlesInitial(
@@ -401,7 +404,10 @@ ActsExamples::Geant4MaterialRecording::~Geant4MaterialRecording() = default;
 
 ActsExamples::ProcessCode ActsExamples::Geant4MaterialRecording::execute(
     const ActsExamples::AlgorithmContext& ctx) const {
-  Geant4SimulationBase::execute(ctx);
+  const auto ret = Geant4SimulationBase::execute(ctx);
+  if (ret != ProcessCode::SUCCESS) {
+    return ret;
+  }
 
   // Output handling: Material tracks
   m_outputMaterialTracks(

Examples/Algorithms/Geant4/src/SensitiveSteppingAction.cpp

@@ -132,8 +132,7 @@ void ActsExamples::SensitiveSteppingAction::UserSteppingAction(
   // Get the physical volume & check if it has the sensitive string name
   const G4VPhysicalVolume* volume = track->GetVolume();
   if (volume == nullptr) {
-    ACTS_ERROR("No volume found for track " << track->GetTrackID());
-    std::terminate();
+    throw std::runtime_error("No volume found, terminate simulation");
   }
   std::string volumeName = volume->GetName();
 

Examples/Io/Root/src/RootSimHitReader.cpp

@@ -72,6 +72,9 @@ RootSimHitReader::RootSimHitReader(const RootSimHitReader::Config& config,
   m_inputChain->SetBranchStatus("event_id", true);
 
   auto nEntries = static_cast<std::size_t>(m_inputChain->GetEntriesFast());
+  if (nEntries == 0) {
+    throw std::runtime_error("Did not find any entries in input file");
+  }
 
   // Add the first entry
   m_inputChain->GetEntry(0);

Examples/Python/python/acts/examples/simulation.py

@@ -724,8 +724,6 @@ def addGeant4(
         sensitiveSurfaceMapper=sensitiveMapper,
         magneticField=field,
         physicsList=physicsList,
-        volumeMappings=volumeMappings,
-        materialMappings=materialMappings,
         killVolume=killVolume,
         killAfterTime=killAfterTime,
         killSecondaries=killSecondaries,

Examples/Python/src/Geant4Component.cpp

@@ -178,8 +178,6 @@ PYBIND11_MODULE(ActsPythonBindingsGeant4, mod) {
     ACTS_PYTHON_MEMBER(sensitiveSurfaceMapper);
     ACTS_PYTHON_MEMBER(magneticField);
     ACTS_PYTHON_MEMBER(physicsList);
-    ACTS_PYTHON_MEMBER(volumeMappings);
-    ACTS_PYTHON_MEMBER(materialMappings);
     ACTS_PYTHON_MEMBER(killVolume);
     ACTS_PYTHON_MEMBER(killAfterTime);
     ACTS_PYTHON_MEMBER(killSecondaries);

Examples/Scripts/Python/geant4.py

@@ -8,12 +8,6 @@
 from acts.examples.simulation import addParticleGun, addGeant4, EtaConfig
 from acts.examples.odd import getOpenDataDetector, getOpenDataDetectorDirectory
 
-from acts.examples.dd4hep import (
-    DD4hepDetector,
-    DD4hepDetectorOptions,
-    DD4hepGeometryService,
-)
-
 u = acts.UnitConstants
 
 
@@ -22,6 +16,7 @@ def runGeant4(
     trackingGeometry,
     field,
     outputDir,
+    materialMappings=["Silicon"],
     s: acts.examples.Sequencer = None,
 ):
     s = s or acts.examples.Sequencer(events=100, numThreads=1)
@@ -41,6 +36,7 @@ def runGeant4(
         outputDirCsv=outputDir / "csv",
         outputDirRoot=outputDir,
         rnd=rnd,
+        materialMappings=materialMappings,
     )
     return s
 
@@ -59,6 +55,12 @@ def runGeant4(
     field = acts.ConstantBField(acts.Vector3(0, 0, 2 * u.T))
 
     if args.experimental:
+        from acts.examples.dd4hep import (
+            DD4hepDetector,
+            DD4hepDetectorOptions,
+            DD4hepGeometryService,
+        )
+
         print(">>> Running experimental geometry <<<")
         odd_xml = getOpenDataDetectorDirectory() / "xml" / "OpenDataDetector.xml"
 

Examples/Scripts/Python/truth_tracking_kalman.py

@@ -15,6 +15,7 @@ def runTruthTrackingKalman(
     digiConfigFile: Path,
     outputDir: Path,
     inputParticlePath: Optional[Path] = None,
+    inputHitsPath: Optional[Path] = None,
     decorators=[],
     directNavigation=False,
     reverseFilteringMomThreshold=0 * u.GeV,
@@ -46,6 +47,8 @@ def runTruthTrackingKalman(
     rnd = acts.examples.RandomNumbers(seed=42)
     outputDir = Path(outputDir)
 
+    logger = acts.logging.getLogger("Truth tracking example")
+
     if inputParticlePath is None:
         addParticleGun(
             s,
@@ -61,9 +64,7 @@ def runTruthTrackingKalman(
             rnd=rnd,
         )
     else:
-        acts.logging.getLogger("Truth tracking example").info(
-            "Reading particles from %s", inputParticlePath.resolve()
-        )
+        logger.info("Reading particles from %s", inputParticlePath.resolve())
         assert inputParticlePath.exists()
         s.addReader(
             acts.examples.RootParticleReader(
@@ -72,14 +73,26 @@ def runTruthTrackingKalman(
                 outputParticles="particles_input",
             )
         )
+        s.addWhiteboardAlias("particles", "particles_input")
 
-    addFatras(
-        s,
-        trackingGeometry,
-        field,
-        rnd=rnd,
-        enableInteractions=True,
-    )
+    if inputHitsPath is None:
+        addFatras(
+            s,
+            trackingGeometry,
+            field,
+            rnd=rnd,
+            enableInteractions=True,
+        )
+    else:
+        logger.info("Reading hits from %s", inputHitsPath.resolve())
+        assert inputHitsPath.exists()
+        s.addReader(
+            acts.examples.RootSimHitReader(
+                level=acts.logging.INFO,
+                filePath=str(inputHitsPath.resolve()),
+                outputSimHits="simhits",
+            )
+        )
 
     addDigitization(
         s,