Function ProcessBooleanExtrudedAreaSolidDifference

code/AssetLib/IFC/IFCBoolean.cpp:672–718

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// ------------------------------------------------------------------------------------------------
void ProcessBooleanExtrudedAreaSolidDifference(const Schema_2x3::IfcExtrudedAreaSolid *as,
        TempMesh &result,
        const TempMesh &first_operand,
        ConversionData &conv) {
    ai_assert(as != nullptr);

    // This case is handled by reduction to an instance of the quadrify() algorithm.
    // Obviously, this won't work for arbitrarily complex cases. In fact, the first
    // operand should be near-planar. Luckily, this is usually the case in Ifc
    // buildings.

    std::shared_ptr<TempMesh> meshtmp = std::make_shared<TempMesh>();
    ProcessExtrudedAreaSolid(*as, *meshtmp, conv, false);

    std::vector<TempOpening> openings(1, TempOpening(as, IfcVector3(0, 0, 0), std::move(meshtmp), std::shared_ptr<TempMesh>()));

    result = first_operand;

    TempMesh temp;

    std::vector<IfcVector3>::const_iterator vit = first_operand.mVerts.begin();
    for (unsigned int pcount : first_operand.mVertcnt) {
        temp.Clear();

        temp.mVerts.insert(temp.mVerts.end(), vit, vit + pcount);
        temp.mVertcnt.push_back(pcount);

        // The algorithms used to generate mesh geometry sometimes
        // spit out lines or other degenerates which must be
        // filtered to avoid running into assertions later on.

        // ComputePolygonNormal returns the Newell normal, so the
        // length of the normal is the area of the polygon.
        const IfcVector3 &normal = temp.ComputeLastPolygonNormal(false);
        if (normal.SquareLength() < static_cast<IfcFloat>(1e-5)) {
            IFCImporter::LogWarn("skipping degenerate polygon (ProcessBooleanExtrudedAreaSolidDifference)");
            continue;
        }

        GenerateOpenings(openings, temp, false, true);
        result.Append(temp);

        vit += pcount;
    }

    IFCImporter::LogVerboseDebug("generating CSG geometry by geometric difference to a solid (IfcExtrudedAreaSolid)");
}

// ------------------------------------------------------------------------------------------------
void ProcessBoolean(const Schema_2x3::IfcBooleanResult &boolean, TempMesh &result, ConversionData &conv) {