G4OCCT_STEPAssembly.cc

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// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2026 G4OCCT Contributors
 
 
// Two header worlds must not meet in the same TU:
//   DD4hep → ROOT → TString.h         declares: extern void Printf(...)
//   G4OCCT → OCCT → Standard_CString.h declares: int Printf(...)
// Keeping them in separate TUs (firewall pattern) resolves both this Printf
// conflict and the Handle(Class) macro collision.
// G4OCCT_STEPAssembly_impl.{hh,cc} is the OCCT-side TU; this file is the
// DD4hep-side TU.
#include <DD4hep/DetFactoryHelper.h>
#include <DD4hep/Printout.h>
 
#include "G4OCCT_STEPAssembly_impl.hh"
 
#include <G4Material.hh>
#include <G4NistManager.hh>
 
#include <map>
#include <stdexcept>
#include <string>
 
using namespace dd4hep;
 
static Ref_t create_step_assembly(Detector& description, xml_h e, SensitiveDetector /*sens*/) {
  xml_det_t x_det   = e;
  xml_comp_t x_step = x_det.child(_Unicode(step_file));
  xml_comp_t x_pos  = x_det.child(_Unicode(position));
  xml_comp_t x_map  = x_det.child(_Unicode(material_map));
 
  std::string name = x_det.nameStr();
  std::string path = x_step.attr<std::string>(_Unicode(path));
 
  // ── Build the material map from the compact XML entries ───────────────────
  std::map<std::string, G4Material*> materials;
  for (xml_coll_t it(x_map, _Unicode(entry)); it; ++it) {
    xml_comp_t x_entry        = it;
    std::string stepName      = x_entry.attr<std::string>(_Unicode(step_name));
    std::string dd4hepMatName = x_entry.attr<std::string>(_Unicode(dd4hep_material));
 
    // Resolve the G4Material via NIST manager (already constructed by DD4hep
    // material loading) — look up by the Geant4 material name.
    G4Material* g4mat = G4NistManager::Instance()->FindOrBuildMaterial(dd4hepMatName);
    if (!g4mat) {
      // Fall back to the Geant4 material table (materials defined inline in the
      // compact file are registered under their compact name, not a NIST name).
      g4mat = G4Material::GetMaterial(dd4hepMatName, /*warn=*/false);
    }
    if (!g4mat) {
      throw std::runtime_error("G4OCCT_STEPAssembly: Geant4 material '" + dd4hepMatName +
                               "' not found for STEP name '" + stepName + "'");
    }
    materials[stepName] = g4mat;
    printout(DEBUG, "G4OCCT_STEPAssembly", "Mapped STEP material '%s' → G4Material '%s'",
             stepName.c_str(), dd4hepMatName.c_str());
  }
 
  // ── Import the STEP assembly (OCCT side, separate TU) ────────────────────
  int nConstituents = G4OCCT_ImportSTEPAssembly(path, materials);
 
  // ── Create a DD4hep assembly container (no per-solid placements here) ────
  // Phase 1 limitation: the STEP assembly is imported on the OCCT side and its
  // constituent G4LogicalVolumes live in the Geant4 volume store, but they are
  // not placed into this dd4hep::Assembly.  The assembly is therefore empty
  // from the TGeo/DD4hep perspective.
  // @todo Phase 2: return per-solid placement data from the OCCT-side TU and
  // populate dd4hepAssembly with TGeo placeholder volumes so DD4hep and
  // visualisation tools can see the constituent geometry.
  Assembly dd4hepAssembly(name + "_assembly");
 
  printout(INFO, "G4OCCT_STEPAssembly",
           "Imported STEP assembly '%s' from '%s'; %d constituent solid(s) on "
           "OCCT side; created empty dd4hep::Assembly '%s' as top-level container",
           name.c_str(), path.c_str(), nConstituents, (name + "_assembly").c_str());
 
  // ── DetElement and placement ─────────────────────────────────────────────
  DetElement det(name, x_det.id());
  Position pos(x_pos.x(), x_pos.y(), x_pos.z());
 
  PlacedVolume pv = description.pickMotherVolume(det).placeVolume(dd4hepAssembly, pos);
  pv.addPhysVolID("system", x_det.id());
  det.setPlacement(pv);
  return det;
}
 
DECLARE_DETELEMENT(G4OCCT_STEPAssembly, create_step_assembly)