G4OCCT_STEPSolid.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 described above.
// G4OCCT_STEPSolid_impl.{hh,cc} is the OCCT-side TU; this file is the
// DD4hep-side TU.
#include <DD4hep/DetFactoryHelper.h>
#include <DD4hep/Printout.h>
#include <TGeoTessellated.h>
 
#include "G4OCCT_STEPSolid_impl.hh"
 
#include <cstddef>
#include <limits>
#include <stdexcept>
#include <string>
 
using namespace dd4hep;
 
static Ref_t create_step_solid(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_rot  = x_det.child(_Unicode(rotation));
  xml_comp_t x_mat  = x_det.child(_Unicode(material));
 
  std::string name = x_det.nameStr();
  std::string path = x_step.attr<std::string>(_Unicode(path));
 
  // ── Import STEP solid and tessellate (OCCT side, separate TU) ───────────
  G4OCCT_STEPSolidGeometry geom = G4OCCT_ImportSTEPSolid(name, path);
 
  printout(INFO, "G4OCCT_STEPSolid", "Imported '%s' from '%s'; %zu triangles in tessellated solid",
           name.c_str(), path.c_str(), geom.triangles.size());
 
  // ── Build a TessellatedSolid for the TGeo/DD4hep representation ──────────
  // TessellatedSolid wraps ROOT's TGeoTessellated: a polyhedral mesh solid
  // that can be visualised and used for navigation by TGeo-based tools.
  // We pass the triangle count as a capacity hint, then add facets one by one.
  const std::size_t nTriangles = geom.triangles.size();
  if (nTriangles > static_cast<std::size_t>(std::numeric_limits<int>::max())) {
    throw std::runtime_error("G4OCCT_STEPSolid: tessellation of '" + path + "' produced " +
                             std::to_string(nTriangles) +
                             " triangles, which exceeds TessellatedSolid's int capacity");
  }
  TessellatedSolid tess(name + "_tess", static_cast<int>(nTriangles));
  for (const auto& tri : geom.triangles) {
    tess.addFacet(TessellatedSolid::Vertex(tri.v[0].x, tri.v[0].y, tri.v[0].z),
                  TessellatedSolid::Vertex(tri.v[1].x, tri.v[1].y, tri.v[1].z),
                  TessellatedSolid::Vertex(tri.v[2].x, tri.v[2].y, tri.v[2].z));
  }
  tess.ptr()->CloseShape(/*check=*/true, /*fixFlipped=*/true, /*verbose=*/false);
 
  // ── DD4hep volume and placement ──────────────────────────────────────────
  Material mat = description.material(x_mat.attr<std::string>(_Unicode(name)));
  Volume vol(name + "_vol", tess, mat);
  vol.setVisAttributes(description, x_det.visStr());
 
  DetElement det(name, x_det.id());
  Position pos(x_pos.x(), x_pos.y(), x_pos.z());
  RotationZYX rot(x_rot.z(), x_rot.y(), x_rot.x());
  PlacedVolume pv = description.pickMotherVolume(det).placeVolume(vol, Transform3D(rot, pos));
  pv.addPhysVolID("system", x_det.id());
  det.setPlacement(pv);
  return det;
}
 
DECLARE_DETELEMENT(G4OCCT_STEPSolid, create_step_solid)