What makes a SubD crease a crease?

What makes a SubD crease a crease? And, when I convert one to a mesh, how can it be identified? I also posted this question in the Grasshopper forum, so please forgive me. Ultimately, I’d like a GH solution, but it doesn’t look like one is forthcoming.

Hello - a crease is a location with only positional continuity - no tangency across the seam. On a SubD each side of a crease will also have zero curvature across that seam. You’d see them with a Zebra analysis mode.


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fwiw, you can also fillet creased edges once the subd is converted to nurbs.

Thank you @pascal and @theoutside for your replies, I did a little experimenting earlier by constructing a curvy SubD, copying it, and adding a crease to the copy. When I converted them both to meshes in GH, all I seemed to see was an additional edge added that was “creasy”, I don’t see anything else about it that distinguishes it from the other “smooth” edges. What am I missing?

Hello - please post a file with the subD and the mesh. The mesh will not be welded across a creased seam, even if in a particular example the shape is not different from uncreased.


You know, I just tried welding the creased version and the crease mostly went away, because there’s still that additional edge. So then the question becomes how to determine where the unwelded vertices are. Any ideas?

SubD crease.3dm (131.4 KB)

Hello - I guess I am not clear on what you are trying to accomplish - if the crease is bad, RemoveCrease on the SubD.


I was hoping to be able to split a mesh at the crease without first converting to nurbs and then picking out all the little pieces.

Hm. You can split the SubD with Split > EdgeLoop - does that get you anything you like?


I don’t see that command…

help>check for updates to get the latest service release, then run toolbarreset to get the latest toolbars.

Sorry Kyle, I still don’t see it. I’m using Rhino 7 SR6 2021-5-7. What am I looking for?

This is a simple GH solution.

As explained, you have to use Mesh Topology Edges to choose which edges should be unwelded / creased.

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Thanks Martin. Since my goal is to be able to split the mesh along creases, I’ll see what I can do with this.

Post an example.

You can use the one a few posts up.

What’s the next step? Why split the mesh?


For “artistic” purposes, I want to treat the pieces differently, leaving some the same and processing others some more, while still maintaining the continuity of the overall shape…

Good, so I’m not blind. At Kyle’s recommendation, I downloaded the latest SR and this is what I see:

I don’t see split along edge loop.
Are you using the new SR candidate?