D = spline (D, SP) appends the geom.Spline SP, open or closed, kept as the exact curve it is rather than as points along it:

 SP = geom.Spline ([0, 0; 20, 15; 45, 10; 60, 30]);
 D = draw.Drawing ().spline (SP);

A drawing is flat, so SP must lie in its xy plane. Its geom.UCS may have its own origin and x axis there and may face down: the drawing keeps the same curve, re-expressed in its own coordinates.

See also: geom.Spline, polyline, path

Source Code: draw.Drawing