Objects creation and modification	Approximating polylines
Rounding polylines
Overview     Operations    Commands

How to round a polyline converting it to a Spline  

1. Click on the menu Modify  Polylines operations...  Polyline: convert to Spline
2. Select the objects to be converted, then press ENTER.
3. If some polyline is closed you will be prompted to round or not the closing point. If the polyline for example is an airfoil, you want to keep the closing point (the tail) sharped.

A message will display the result of the operation.

Here is an example of a sharped polyline (an airfoil) :

A detail of the sharped nose of the polyline:

and the result is (selecting to keep the tail sharped):

A detail of the smoothed nose of the new spline:

 Command line: TO_SPLINE