Hi Pilou,

The problem is with getting and preserving the tangents at the beginning and end.
I am unable to extract the two tangents by clicking on the curve(s), using scripts.
(This is do-able using Nurbs equations, for an expert, for example the blend command.)
So instead, helper tangent lines are used.
A few months ago I did a script to utilize two helper line segments, at the beginning and end, which are
placed manually, as tangents. However, using the interpcurve or curve factories, to draw the clothoid, resulted
in a clothoid curve which were close to being tangent, but were not quite tangent, so the code was never polished up.
I may revisit it sometime. I do not want to post "sloppy" code, and try to polish it up, at least somewhat...

When I am tracing curve drawings using an image, Blend often works well. Sometimes a clothoid is very helpful, used to
help establish a curve, which blend can alter.

(Note that the factory curves are close approximations to such curves as clothoids, catenaries, sinewaves, etc.)

- Brian

Edit: I have not made a website yet :-)