Hi everyone,
I’m working with the clipper plugin (specifically, offset curves), but it works only on planar curves, while I need to work on non-planar ones and surfaces. I tried to project the non-planar isocurve but I don’t know how to going on.

Not sure what you want, but if you want to define the plane for Clipper for each isocurve, you can use the Planar component which gives the “best” approximation of the plane containing the curve.

yeah sorry, I know that is a little bit strange my question, but it is related to a bigger work and this is just a little simplified part😅

Anyway thank you for your answer, but I believe that my problem still remains. Because if you observe the isocurve (fig.1) the offset curves (fig.2) don’t match with the first ones (fig.3). For this reason I tried to project all the curves and then re-project on the non-planar surfaces.

Well, at least I see what you don’t want. Can you show what you mean by “project” for one of these curves. Are you trying, for example, to offset the curve normal to the direction of its tangent at each point, and in what direction, up, down, in some plane?

Here, each curve is offset, normal to direction of its tangent, and parallel to the xy plane.