INQ: Documentation of Exchange Requirement setting

[thumDer]

Inquiry description

Currently there is no information about what is the effect of changing the Exchange Requirement when exporting IFC4. Browsing the code the only clues I've found, that if it is Structural, then

• it exports parts: https://github.com/Autodesk/revit-ifc/blob/6498fbdae7f3889708ebded66d90ca829d165f82/Source/Revit.IFC.Export/Exporter/PartExporter.cs#L985

    /// <summary>
    /// Identifies if the host element should be exported as parts.
    /// If MVD is older then IFC4 we rely on ExportOptionsCache.ExportParts option.
    /// If MVD is IFC4RV and if Exchange type is Structural we need to export Parts if they exist. If number of parts is 1 we need to export it as ShapeAspect and not as Part.
    /// </summary>
    /// <param name="hostElement">The host element.</param>
    /// <param name="layersCount">The number of layers or parts the hostElemnt consists of.</param>
    /// <returns>True if host element should be exported as parts, false otherwise.</returns>
    public static bool ShouldExportParts(Element hostElement, int layersCount)
    {
       return hostElement != null && (ExporterCacheManager.ExportOptionsCache.ExportParts ||
          (ExporterCacheManager.ExportOptionsCache.ExportAs4ReferenceView &&
          ExporterCacheManager.ExportOptionsCache.ExchangeRequirement == KnownERNames.Structural &&
          layersCount > 1));
    }

• exports ramps as IFCSlabs: https://github.com/Autodesk/revit-ifc/blob/6498fbdae7f3889708ebded66d90ca829d165f82/Source/Revit.IFC.Export/Exporter/RampExporter.cs#L714

    static IFCExportInfoPair CreateRampExportInfoPair(IFCEntityType entityName, IFCEntityType entityType, string predefType)
    {
       // For IFC4 and Structural Exchange Requirement export, ramps will be exported as IFCSlab type
       if (ExporterCacheManager.ExportOptionsCache.ExportAs4 && 
          (ExporterCacheManager.ExportOptionsCache.ExchangeRequirement == KnownERNames.Structural))
       {
          entityName = IFCEntityType.IfcSlab;
          entityType = IFCEntityType.IfcSlabType;
       }
  
       return new IFCExportInfoPair(entityName, entityType, predefType);
    }

Are there anything else?

Revit Version

2024.0.x

IFC for Revit Addon Version

24.x.x

Windows Version

11 22H2

[AngelVelezSosa]

buildingSMART has some specification of what the different exchange requirements are supposed to do: (https://standards.buildingsmart.org/MVD/RELEASE/IFC4/ADD2_TC1/RV1_2/HTML/schema/views/reference-view/index.htm)