buildSolid.cc

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// gemc
#include "gutilities.h"
 
// g4system
#include "cadSystemFactory.h"
 
// ───────────────── CADMesh single-header library ────────────────
// https://github.com/christopherpoole/CADMesh
//
// *Modifications applied to the vendor header:*
//   - Marked the following classes `final`
//       • BuiltInReader
//       • TessellatedMesh
//   - Reason: https://devblogs.microsoft.com/oldnewthing/20200619-00/?p=103877
//
// *Optional Dependencies*
// Define `USE_CADMESH_ASSIMP_READER` **before** including `CADMesh.hh`
// to enable Assimp-based file loading.
//
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// !!! SET THIS BEFORE INCLUDING CADMESH.HH TO USE THE ASSIMP READER
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
#define USE_CADMESH_ASSIMP_READER
// If you want Assimp to be the default reader, uncomment:
// #define CADMESH_DEFAULT_READER ASSIMP
 
#include "CADMesh.hh"
 
// Geant4 units
#include "CLHEP/Units/SystemOfUnits.h"
 
namespace {
    bool numeric_value(const std::string& value, double& result) {
        try {
            size_t parsed = 0;
            result = std::stod(value, &parsed);
            return parsed == value.size();
        }
        catch (const std::exception&) { return false; }
    }
}
 
G4VSolid* G4CadSystemFactory::buildSolid(const GVolume* s,
                                         std::unordered_map<std::string,
                                                            G4Volume*>* g4s) {
    std::string g4name = s->getG4Name();
 
    // Dependency check: solids can require other solids (copy/boolean operations).
    if (!checkSolidDependencies(s, g4s)) return nullptr;
 
    // Locate or allocate the wrapper used to cache solid/logical/physical pointers.
    auto thisG4Volume = getOrCreateG4Volume(g4name, g4s);
    if (thisG4Volume->getSolid() != nullptr) return thisG4Volume->getSolid();
 
    // If this is a copy of another volume, reuse the source mesh solid instead of loading a mesh:
    // the copy carries no mesh file of its own (e.g. the LTCC frame plates placed in every sector).
    const auto& copyOf = s->getCopyOf();
    if (copyOf) {
        auto sourceName     = s->getSystem() + "/" + *copyOf;
        auto sourceG4Volume = getOrCreateG4Volume(sourceName, g4s);
        if (sourceG4Volume->getSolid() != nullptr) return sourceG4Volume->getSolid();
    }
 
    // Current rows store "<mesh path>, <scale>" in parameters. For compatibility, an old row may
    // store only its numeric scale there and its mesh path in description.
    std::string fileName = s->getDescription();
    double      scale    = 1.0;
    std::vector<std::string> cadParameters;
    if (s->getParameters()) {
        cadParameters = gutilities::getStringVectorFromStringWithDelimiter(*s->getParameters(), ",");
    }
    if (cadParameters.size() > 1) {
        fileName = cadParameters[0];
        if (!numeric_value(cadParameters[1], scale)) {
            log->warning("G4CadSystemFactory: volume <", g4name,
                         "> has a non-numeric scale <", cadParameters[1], ">; using 1.0");
            scale = 1.0;
        }
    }
    else if (cadParameters.size() == 1) {
        double legacyScale = 1.0;
        if (numeric_value(cadParameters[0], legacyScale)) { scale = legacyScale; }
        else { fileName = cadParameters[0]; }
    }
 
    G4String    g4filename = fileName;
 
    // File extension (last token after '.').
    std::string extension =
        gutilities::getStringVectorFromStringWithDelimiter(fileName, ".").back();
 
    // PLY / STL via CADMesh & Assimp reader.
    if (extension == "ply" || extension == "stl") {
        auto mesh = CADMesh::TessellatedMesh::From(g4filename,
                                                   CADMesh::File::ASSIMP());
 
        // The CAD file is interpreted in millimetres (times the per-volume scale) to match
        // typical detector CAD conventions.
        mesh->SetScale(CLHEP::mm * scale);
 
        // Do not flip vertex winding unless the CAD source requires it.
        mesh->SetReverse(false);
 
        thisG4Volume->setSolid(mesh->GetSolid(), log);
        return thisG4Volume->getSolid();
    }
 
    // Unsupported extension: return nullptr so the caller can decide whether to treat it as fatal.
    log->warning("G4CadSystemFactory: file <", fileName,
                 "> has unsupported extension <", extension, ">");
    return nullptr;
}