Hi Thibaud, also if you send me an e-mail (moi@moi3d.com), I can send you an update patch that will avoid doing this tangent alignment in cases like this where there are 2 line segments adjacent to one another but close to being tangent with each other.

That's happening in your case since the curved looking areas are not really curves, but are instead a whole bunch of little lines.

If those curved areas were made up of longer actual curved spline pieces instead of little lines, that problem wouldn't actually happen because the tangent of the curved piece would be adjusted to be trued up, and not the line segment piece.

- Michael