Polyline to Single Degree 1 Curve - How?

How can I convert a polyline to a single degree 1 curve? Match with the merge option does not work because the merge option is disabled for position matching.

The reason for converting the polyline to a single degree 1 curve is to simplify editing the line/curve using control points and eliminate gaps from occurring by mistake.

MergeSrf works to create for pairs of surfaces which are degree 1 in the direction normal to the coincident edges. The result is a single multi-span surface of degree 1 in the appropriate direction.

If you use Rebuild and make it degree 1 with 2 control points, it will be a straight line.
Is that what you’re after?


I’m starting with a polyline which has multiple straight line segments. I want the result to be degree 1 multispan curve with exactly the same shape.

I found the answer - CurveThroughPolyline with Degree=1 CurveType=Interpolated or CurveType=ControlPoint does not appear to make any difference in the result.

Hi David - ToNurbs will also do it.


@Pascal Thanks, I tried ToNurbs and it worked. Simpler to use than CurveThroughPolyline, but completely undocumented. It is not in the Command Quick Reference list, and a search of V6 Help doesn’t return anything relevant. Also does not auto-complete.

ToNurbs appears to be new in V6. Did someone forget to document it? How would a user know about it?

Hi David - ToNurbs may be, officially, a test command - it was deemed, at the last minute, not done enough - I don’t remember what the shortcomings were off hand and I don’t think they’ve been addressed yet…


I’ll let you know if I find any problems or shortcomings with it.

For a curve, probably just calls RhinoCommon Curve.ToNurbsCurve() and if it succeeds, replaces the original… For something like an extrusion, same thing, using Extrusion.ToNurbsSurface(). I assume…