Use NURBS curves to model arbitrary shapes in 3D. NURBS curves are automatically generated from a series of successive points. NURBS curves and polycurves can be combined to generate almost any geometry. NURBS curves can also be specified as extrusion paths, which enables generating curved linear elements with uniform cross-section. For example, a cross-section defined by a polygon or polycurve can be extruded along the trajectory defined by a NURBS curve.