Trouble getting surface to match wireframe

Hello. Newbie here. I am trying to make a signet-style ring. I have the profiles of the ring precisely defined with curves where I want them. I want a smooth, seamless surface over it. How should I approach this problem?

Here is what I tried:

One portion has 5 edges instead of 4. This seemed like a good candidate for the patch tool. The problem is that the patch, when mirrored, has visible seams. I tried to work around this by extruding the three edges that must be seamless, then matching the patch to the tangency of the created surface edges. There were still visible seams after mirroring for some reason.

Something I have seen in a few ring tutorials which almost achieves what I’m going for is bridging the two curves that appear vertical in front view, then using rail sweep or surface from network and boring the hole through the surface after. In case that description is unclear, here’s an example. The only problem with that is it doesn’t give me any control over the shape or position of the edge where the hole is. I would like my surface to intersect perfectly every part of my wireframe.

Your input is appreciated.
Thank you for your time,

ring_helpme.3dm(73.2 KB)

Hi Leopold,

How about this approach, I joined all partial curves and added an (edited) blend between the ends at the top to form a single shape that can be trimmed at the top and make a blend towards the reference cone.
ring_helpme_WD.3dm(164.0 KB)

See the names of different layers for some more guidance,

Thank you very much for the reply. That seems to have solved my problem. I’ve studied your file for a while now and still can’t seem to figure out exactly how you did it. I think I understand how the blend at the top was formed and the reference cone seems easy enough, but I’m still not clear on how they were used. I can’t figure out how you formed the curve that divides the ring into those top and bottom pieces or which surfaces you blended to create that layer. Sorry I’m slow. For the sake of my own learning, would you mind providing a simpler step-by-step of what you did?


Hi Leopold,

I tried to illustrate the process below, let me know if that explains it better.



I get it now! I hadn’t understood the extruded line was eyeballed. I was trying to avoid eyeballing anything but for that step it doesn’t really matter. The initial curve network surface is almost perfect, but the trimmed top portion isn’t quite a perfect circle. Chopping it in the middle and then blending it to the cone allows that top circle to be perfect again. That’s brilliant. I’m so excited. That puzzle had been nagging me for weeks and in almost no time you not only solved it but expressed it with clear diagrams for me. You are a saint, sir. My thanks to you.


Hi Leopold,

Glad I could help! I guess my 10+ years of working with Rhino made me come up with a solution that quick.
However what you probably experienced in the past weeks is, that the trial and error when thinking about and attempting to solve this made you explore many options and possibilities that Rhino offers.

I used to teach Rhino for a couple of years and what in my opinion is paramount when learning Rhino, is not to compromise. Your need to make the top a true circle and persevere until you had that right is the best way to learn Rhino in depth.


Just wanted to update this thread as well. Here’s a video of @Willem’s trick I posted on