private void AddSpringElement(MeshBuilder bldr, Spring1D elm)
        {
            PolygonYz section = null;

            var r = ElementVisualThickness / 2;

            if (elm.StartNode.Location.Equals(elm.EndNode.Location))
            {
                bldr.AddSphere(new Point3D(elm.StartNode.Location.X,
                                           elm.StartNode.Location.Y,
                                           elm.StartNode.Location.Z), ElementVisualThickness * 3);
            }
        }
 private void AddNode(MeshBuilder bldr, Node nde)
 {
     bldr.AddSphere(new Point3D(nde.Location.X, nde.Location.Y, nde.Location.Z),
                    ElementVisualThickness * 2, 20, 20);
 }