The thread about B-splines has led me to read about Ikarus.
There's something I don't understand:
If all segments are circle arcs, how do you approximate an ellipse, for example?
(I mean, just like it's possible to approximate an ellipse by a polygon, obviously it's possible to approximate an ellipse using circle arcs. You can even avoid cusps. But it would be very not smooth in the mathematical sense: it won't even have a second derivative. That sounds to me like a big problem. Or maybe it's not?)