public CylinderLayer CreateNewLayer(double zLow)
        {
            CylinderLayer layer = new CylinderLayer(zLow);

            Add(layer);
            return(layer);
        }
        private BBox3D ComputeLoadBBox3D()
        {
            BBox3D bbox   = new BBox3D();
            int    iLayer = 0;

            while (iLayer < Count)
            {
                ILayer        layer  = this[iLayer];
                CylinderLayer blayer = layer as CylinderLayer;
                if (null != blayer)
                {
                    bbox.Extend(blayer.BoundingBox(Analysis.CylinderProperties));
                }
                ++iLayer;
            }
            return(bbox);
        }