No tangency continuity at 7 surface meeting point

I converted a pretty “worst case scenario” file that I found on a different forum:

It faired pretty well, but in this one particular area, I couldn’t even get tangency:

Hi @eobet,

Can you post your 3dm file (or just the problematic part of it) and the Rhino 7 version you are using? @chuck has been working on improving surface tangency in ToNurbs (, maybe he can help you here.

Well, as I said, I found the file in the linked thread. Here’s the mesh I imported into Rhino, in case you don’t have Blender installed: (1.1 MB)

I’m using the second to last newest WIP, because this problem popped up for me again…

Thanks, I’d looked through the thread you linked but did not realize we were looking at a feather of the swan. I still can’t quite find which one you are looking at, so I selected one that’s close enough and isolated it in the attached 3dm file. Red faces here:


Turning on G2 continuity in ToNurbs yields better results, but at the expense of a “wavy” surface around the exceptional node:

I’ve logged the issue here.

RH-60635.3dm (183.3 KB)

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RH-60635 is fixed in the latest Service Release Candidate

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