/// <summary>
        /// Exports curtain object as one Brep.
        /// </summary>
        /// <param name="allSubElements">
        /// Collection of elements contained in the host curtain element.
        /// </param>
        /// <param name="wallElement">
        /// The curtain wall element.
        /// </param>
        /// <param name="exporterIFC">
        /// The ExporterIFC object.
        /// </param>
        /// <param name="setter">
        /// The PlacementSetter object.
        /// </param>
        /// <param name="localPlacement">
        /// The local placement handle.
        /// </param>
        /// <returns>
        /// The handle.
        /// </returns>
        public static IFCAnyHandle ExportCurtainObjectCommonAsOneBRep(ICollection <ElementId> allSubElements, Element wallElement,
                                                                      ExporterIFC exporterIFC, PlacementSetter setter, IFCAnyHandle localPlacement)
        {
            IFCAnyHandle prodDefRep = null;
            Document     document   = wallElement.Document;
            double       eps        = UnitUtil.ScaleLength(document.Application.VertexTolerance);

            IFCFile      file           = exporterIFC.GetFile();
            IFCAnyHandle contextOfItems = exporterIFC.Get3DContextHandle("Body");

            IFCGeometryInfo info = IFCGeometryInfo.CreateFaceGeometryInfo(eps);

            ISet <IFCAnyHandle> bodyItems = new HashSet <IFCAnyHandle>();

            // Want to make sure we don't accidentally add a mullion or curtain line more than once.
            HashSet <ElementId> alreadyVisited = new HashSet <ElementId>();
            bool    useFallbackBREP            = true;
            Options geomOptions = GeometryUtil.GetIFCExportGeometryOptions();

            foreach (ElementId subElemId in allSubElements)
            {
                Element         subElem  = wallElement.Document.GetElement(subElemId);
                GeometryElement geomElem = subElem.get_Geometry(geomOptions);
                if (geomElem == null)
                {
                    continue;
                }

                if (alreadyVisited.Contains(subElem.Id))
                {
                    continue;
                }
                alreadyVisited.Add(subElem.Id);


                // Export tessellated geometry when IFC4 Reference View is selected
                if (ExporterUtil.IsReferenceView())
                {
                    BodyExporterOptions bodyExporterOptions = new BodyExporterOptions(false);
                    IFCAnyHandle        triFaceSet          = BodyExporter.ExportBodyAsTriangulatedFaceSet(exporterIFC, subElem, bodyExporterOptions, geomElem);
                    if (!IFCAnyHandleUtil.IsNullOrHasNoValue(triFaceSet))
                    {
                        bodyItems.Add(triFaceSet);
                        useFallbackBREP = false;    // no need to do Brep since it is successful
                    }
                }
                // Export AdvancedFace before use fallback BREP
                else if (ExporterUtil.IsDesignTransferView())
                {
                    BodyExporterOptions bodyExporterOptions = new BodyExporterOptions(false);
                    IFCAnyHandle        advancedBRep        = BodyExporter.ExportBodyAsAdvancedBrep(exporterIFC, subElem, bodyExporterOptions, geomElem);
                    if (!IFCAnyHandleUtil.IsNullOrHasNoValue(advancedBRep))
                    {
                        bodyItems.Add(advancedBRep);
                        useFallbackBREP = false;    // no need to do Brep since it is successful
                    }
                }

                if (useFallbackBREP)
                {
                    ExporterIFCUtils.CollectGeometryInfo(exporterIFC, info, geomElem, XYZ.Zero, false);
                    HashSet <IFCAnyHandle> faces = new HashSet <IFCAnyHandle>(info.GetSurfaces());
                    IFCAnyHandle           outer = IFCInstanceExporter.CreateClosedShell(file, faces);

                    if (!IFCAnyHandleUtil.IsNullOrHasNoValue(outer))
                    {
                        bodyItems.Add(RepresentationUtil.CreateFacetedBRep(exporterIFC, document, outer, ElementId.InvalidElementId));
                    }
                }
            }

            if (bodyItems.Count == 0)
            {
                return(prodDefRep);
            }

            ElementId    catId = CategoryUtil.GetSafeCategoryId(wallElement);
            IFCAnyHandle shapeRep;

            // Use tessellated geometry in Reference View
            if (ExporterUtil.IsReferenceView() && !useFallbackBREP)
            {
                shapeRep = RepresentationUtil.CreateTessellatedRep(exporterIFC, wallElement, catId, contextOfItems, bodyItems, null);
            }
            else if (ExporterUtil.IsDesignTransferView() && !useFallbackBREP)
            {
                shapeRep = RepresentationUtil.CreateAdvancedBRepRep(exporterIFC, wallElement, catId, contextOfItems, bodyItems, null);
            }
            else
            {
                shapeRep = RepresentationUtil.CreateBRepRep(exporterIFC, wallElement, catId, contextOfItems, bodyItems);
            }

            if (IFCAnyHandleUtil.IsNullOrHasNoValue(shapeRep))
            {
                return(prodDefRep);
            }

            IList <IFCAnyHandle> shapeReps = new List <IFCAnyHandle>();

            shapeReps.Add(shapeRep);

            IFCAnyHandle boundingBoxRep = BoundingBoxExporter.ExportBoundingBox(exporterIFC, wallElement.get_Geometry(geomOptions), Transform.Identity);

            if (boundingBoxRep != null)
            {
                shapeReps.Add(boundingBoxRep);
            }

            prodDefRep = IFCInstanceExporter.CreateProductDefinitionShape(file, null, null, shapeReps);
            return(prodDefRep);
        }