G4OCCT_STEPAssembly_impl.cc

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// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2026 G4OCCT Contributors
 
 
#include "G4OCCT_STEPAssembly_impl.hh"
 
#include "G4OCCT/G4OCCTAssemblyVolume.hh"
#include "G4OCCT/G4OCCTMaterialMap.hh"
 
#include <map>
#include <stdexcept>
#include <string>
 
class G4Material;
 
int G4OCCT_ImportSTEPAssembly(const std::string& path,
                              const std::map<std::string, G4Material*>& materials) {
  G4OCCTMaterialMap matMap;
  for (const auto& [stepName, g4mat] : materials) {
    matMap.Add(stepName, g4mat);
  }
 
  G4OCCTAssemblyVolume* assembly = nullptr;
  try {
    assembly = G4OCCTAssemblyVolume::FromSTEP(path, matMap);
  } catch (const std::exception& ex) {
    throw std::runtime_error("G4OCCT_STEPAssembly: failed to import '" + path + "' (" + ex.what() +
                             ")");
  }
 
  // Extract the constituent count before releasing the assembly.
  // G4OCCTAssemblyVolume::FromSTEP() returns a heap-allocated object owned by
  // the caller.  We only need the count here; the G4 logical volumes that
  // FromSTEP() registered in the Geant4 volume store remain valid after this.
  const int nConstituents = static_cast<int>(assembly->GetLogicalVolumes().size());
  delete assembly;
  assembly = nullptr;
  return nConstituents;
}