A conversion issue or a join issue?

After selecting edge loops of a SubD object and converting contiguous ones to Nurbs, and then joining those into one smooth curve, the Mid Osnap function has a problem. It will still snap to the midpoints of where each unjoined segment was as if they were not joined and it will not snap to the midpoint of the complete new curve which was resultant from the join.

Hi Dale -

I’m not following what you are doing there.
Apart from that, it is expected behavior that Rhino will snap to the individual midpoints of a polycurve.

@wim Did you miss this part of Dale’s post?

Al - did you miss this part?

I tried a few things but if you have the exact steps that are involved here, please let me know.

Join command used on curves results in polycurves, independent of the continuity/smoothness between the individual curves.

To create a single curve from multiple curves use Match with Curvature continuity and the Merge option.selected. Note that the resulting curve may have multiknots. The Mid Osnap will be at the middle of the new curve.

you made a polycurve when you did that, you’d need to use the rebuild or match curvature with merge option it to get a continuous curve. The behavior you are seeing is as designed.

Rebuild will almost always result in a change in the shape of the curve, which may or may not be a problem.

Thank you.

this is true, but unavoidable if they want a single curve. They will likely have to so some adjusting/fairing to get the curve they want.

Thankfully, that’s not an issue in my particular instance. I’m using it for a surface that I will be trimming later, and it is not a complicated curve.

If it were more critical, I suppose building a curve from the control points from the converted SubD segments would be close.

Not unavoidable. Use Match with Curvature matching and Merge and the result is a single curve with exactly the same shape as the input curves. There may be multiknots which can be removed with RemoveMultiknot which in my experience in this use usually does not change the shape