Offset SubD

Hello, I would like to shift a subD surface and when I shift it it’s as if it remains partially stuck to my base surface instead of having the same surface identically shifted. Can you help me?
Thanks in advance, have a nice day.

Hi Melvin - What does ‘shift’ mean? What command are you using? Can you post a file with the misbehaving object?


Hello, sorry I can’t send you the file because it is too heavy. In my previous message I made a mistake, I wanted to say that I can’t shift my subD surface correctly. If you want, it’s as if the shifted surface shifts while remaining glued. Here is a picture.

Uploading: Capture d’écran 2022-06-20 à 19.19.18.png…

What is “shift”? There’s no shift command in Rhino, so we have no idea what you are talking about. What command(s) are you using?
Also, you can use SaveSmall to reduce the filesize or upload the file here and refer to this post.
HTH, Jakob

How did you create this SubD?

It could most probably be done with much less quads…

Yes but it is important that there are as many because it represents the exact shape. Do you have any idea why the object doesn’t shrink simply by shifting?

What is shift supposed to do?

Ah I understood, if you want the surface to bend and suddenly when I shift the surface, it is too big and suddenly passes through the object. Know how can we offset a variable surface that adapts to the object? Thanks.

Hi @Melvin
Ah, so it’s OffsetSubD you are talking about - good to know!
You’ll never get the attached subd to offset cleanly - there are quite a few areas where the topology is less than optimal. Main problem are is the top, where the edge folds in on itself twice. You’ll have to clean this up for the offset to work. I’ve pulled the edges apart, so that you can see how they overlap.

Also, there are several places where the curvature of the existing surface it too tight to fit a 1.3mm offset. You’ll have to either use a smaller offset or “loosen” the curvature (or you can convert to NURBS and build the transitions manually from the offset).
The topology in the corners should probably be simplified as well - this (and the opposing) area is not a good subd layout:

HTH, Jakob

Hello, thank you for your answer, how can I do a trasition manually on a NURBS object? Thanks.

Hi @Melvin
If you are going that route, I would do it by converting the subd to nurbs, offset the surface with Solid=No and then manually cut out “strips” where the surface self-intersects, replacing them with surfaces made with BlendSrf. It’s going to be a LOT of manual work and will of course mean small variations in the surface thickness. What is the end target here; rendering, 3D print, manufacture? If it’s rendering, I’d probably just leave the self-intersections there, unless you need to get really close. If it’s 3D print, you could probably get away with meshing the surface and using OffsetMesh - a lot 3D printers/slicers will eat up self-intersecting meshes like cake. If this needs to be manufactured/moulded in eg. plastic, theres no way around all the manual work (or loosening the curvature to fit your 1.3mm thickness). 1.3mm is quite thick for such a small object with that amount of detail :grimacing:

Thanks for your help, have a nice day.