Hi Fabien, yes your desired result does look like the control polygon of a curve so try doing a regular curve rebuild and then extracting the control polygon like Burr writes above. Yours kind of looks more like a quadratic curve's control polygon so you might try doing a FitCrv in Rhino with Degree=2 and see if that's closer or not.

> I think three would be too low to represent such a curve at all, no?

Yes I think so but that can kind of indicate that what you're asking for is not very well defined as a specific algorithm. A script needs to follow some specific steps.

- Michael