/// <summary>
        /// Creates a simple swept solid from a list of curve loops.
        /// </summary>
        /// <param name="exporterIFC">The exporter.</param>
        /// <param name="profileName">The profile name.</param>
        /// <param name="profileCurveLoops">The profile curve loops.</param>
        /// <param name="normal">The normal of the plane that the path lies on.</param>
        /// <param name="directrix">The path curve.</param>
        /// <returns>The swept solid handle.</returns>
        public static IFCAnyHandle CreateSimpleSweptSolid(ExporterIFC exporterIFC, string profileName, IList <CurveLoop> profileCurveLoops,
                                                          XYZ normal, Curve directrix)
        {
            // see definition of IfcSurfaceCurveSweptAreaSolid from
            // http://www.buildingsmart-tech.org/ifc/IFC2x4/rc4/html/schema/ifcgeometricmodelresource/lexical/ifcsurfacecurvesweptareasolid.htm

            IFCAnyHandle simpleSweptSolidHnd = null;

            if (profileCurveLoops.Count == 0)
            {
                return(simpleSweptSolidHnd);
            }

            IFCFile file = exporterIFC.GetFile();

            XYZ startPoint         = directrix.get_EndPoint(0);
            XYZ profilePlaneNormal = null;
            XYZ profilePlaneXDir   = null;
            XYZ profilePlaneYDir   = null;

            IFCAnyHandle curveHandle = null;

            double startParam = 0, endParam = 1;
            Plane  scaledReferencePlane = null;

            if (directrix is Line)
            {
                Line line = directrix as Line;
                startParam         = 0.0;
                endParam           = 1.0;
                profilePlaneNormal = line.Direction;
                profilePlaneYDir   = normal;
                profilePlaneXDir   = profilePlaneNormal.CrossProduct(profilePlaneYDir);

                XYZ linePlaneNormal = profilePlaneYDir;
                XYZ linePlaneXDir   = profilePlaneXDir;
                XYZ linePlaneYDir   = linePlaneNormal.CrossProduct(linePlaneXDir);
                XYZ linePlaneOrig   = startPoint;

                scaledReferencePlane = GeometryUtil.CreateScaledPlane(exporterIFC, linePlaneXDir, linePlaneYDir, linePlaneOrig);
                curveHandle          = GeometryUtil.CreateLine(exporterIFC, line, scaledReferencePlane);
            }
            else if (directrix is Arc)
            {
                Arc arc = directrix as Arc;

                // profilePlaneXDir is set relative to the startPoint of the directrix.  This effectively resets the start parameter to 0.0, and end parameter = length of curve.
                startParam = 0.0;
                endParam   = (MathUtil.PutInRange(arc.get_EndParameter(1), Math.PI, 2 * Math.PI) - MathUtil.PutInRange(arc.get_EndParameter(0), Math.PI, 2 * Math.PI)) * (180 / Math.PI);

                profilePlaneNormal = directrix.ComputeDerivatives(0, true).BasisX;
                profilePlaneXDir   = (arc.Center - startPoint).Normalize();
                profilePlaneYDir   = profilePlaneNormal.CrossProduct(profilePlaneXDir).Normalize();

                XYZ arcPlaneNormal = arc.Normal;
                XYZ arcPlaneXDir   = profilePlaneXDir;
                XYZ arcPlaneYDir   = arcPlaneNormal.CrossProduct(arcPlaneXDir);
                XYZ arcPlaneOrig   = startPoint;

                scaledReferencePlane = GeometryUtil.CreateScaledPlane(exporterIFC, arcPlaneXDir, arcPlaneYDir, arcPlaneOrig);
                curveHandle          = GeometryUtil.CreateArc(exporterIFC, arc, scaledReferencePlane);
            }
            else
            {
                return(simpleSweptSolidHnd);
            }

            IFCAnyHandle referencePlaneAxisHandle = ExporterUtil.CreateAxis(file, scaledReferencePlane.Origin, scaledReferencePlane.Normal, scaledReferencePlane.XVec);
            IFCAnyHandle referencePlaneHandle     = IFCInstanceExporter.CreatePlane(file, referencePlaneAxisHandle);

            Plane profilePlane = new Plane(profilePlaneXDir, profilePlaneYDir, startPoint);

            IList <CurveLoop> curveLoops = null;

            try
            {
                // Check that curve loops are valid.
                curveLoops = ExporterIFCUtils.ValidateCurveLoops(profileCurveLoops, profilePlaneNormal);
            }
            catch (Exception)
            {
                return(null);
            }

            if (curveLoops == null || curveLoops.Count == 0)
            {
                return(simpleSweptSolidHnd);
            }

            IFCAnyHandle sweptArea = ExtrusionExporter.CreateSweptArea(exporterIFC, profileName, curveLoops, profilePlane, profilePlaneNormal);

            if (IFCAnyHandleUtil.IsNullOrHasNoValue(sweptArea))
            {
                return(simpleSweptSolidHnd);
            }

            profilePlane = GeometryUtil.GetScaledPlane(exporterIFC, profilePlane);
            IFCAnyHandle solidAxis = ExporterUtil.CreateAxis(file, profilePlane.Origin, profilePlane.Normal, profilePlane.XVec);

            simpleSweptSolidHnd = IFCInstanceExporter.CreateSurfaceCurveSweptAreaSolid(file, sweptArea, solidAxis, curveHandle, startParam,
                                                                                       endParam, referencePlaneHandle);
            return(simpleSweptSolidHnd);
        }