Why would CurveNearSurface change BlendSrf this much?

Very funny results with “Tangency” and “Preserve isocurve direction” happen on your sample model. :smiley: Looks like Rhino gets super confused in trying to figure out the desired direction.

I always wondered why Rhino does not use a common direction for the entire edge to be matched? (especially for the “Match target isocurve direction” option) :slight_smile: In many cases, different portions of the same edge go to totally different directions, which does not make any sense and basically destroys the intent of the modeler. The proper way would be for Rhino to use the direction that corresponds to the majority of the edge.