How can I move border on a SURFACE (nurbs not poly) in Rhino like Maya?

with referenced to Maya

How can I move border on a SURFACE (nurbs not poly) in Rhino […]

SrfSeam, perhaps?

SrfSeam only work on Closed Surface - What is a closed surface if a nurbs cylinder is not regarded as a closed surface?

If you have a closed cylinder it is a polysurface (3 surfaces).

If you want to move the seam, you will need to explode the polysurface and select the surface with the seam.

An uncapped cylinder is a closed surface in the sense that two of its edges are joined to one another.

Thanks - so you are saying srf seam is a poly tool and not a nurbs tool?

I wish Rhino was clear about what a close surface is - a cylinder with cap is technically a closed surface.

No, that’s a polysurface. Not to be confused with a mesh (as I understand your “poly tool” comment).

I tried to “explode” the mesh cylinder and deleted the caps and srfseam worked on the remaining tube - apparently explode works on nurbs (mesh?) in Rhino (unlike maya) - thank you!

I really suggest you start looking at some very basic tutorials about Rhino.
You did not “explode” a mesh cylinder. You exploded a NURBS polysurface.

all the basic tutorials on youtube are not fundamental - and then I tried the basic ones step by step and the results are different.
as seen here - time 33:1

And then there is the nomenclature.
In Maya there are nurbs, poly and subD - the tools for each are all different because algorithms behind these 3 modeling categories are all different. Rhino made no efforts at all to distinct this fundamental different in any of their tutorials and learning tools which makes learning impossible.

In maya there is no such thing as Nurbs polysurface. Nurbs and Polysurfaces are two completely different thing. Its like saying a “vector rasterized image”. :woman_shrugging:

Hi @copy_cat
I think you might be mixing up polygons and polysurface. Nurbs is the geometry type that Rhino mainly deals in. It’s the mathematical basis for creating geometry in Rhino. At its core, every single Nurbs surface is 4-sided and can be scaled up or down without loosing its detail - exactly like vector-based artwork in eg. Illustrator. Polygons on the other hand are a lot more like bitmap images. You have a number of polygons (aka polys) and those triangles/quads/ngons are finite, meaning that the “resolution” of the geometry is fixed - unless you employ some sort of sub-dividing algorithm, eg. Catmull-Clark.
Polysurfaces in Nurbs is simply “more than one surface” joined together, poly meaning multiple in ancient Greek. If it’s a closed polysurface, it’s a set of Nurbs surfaces where none of the edges are “naked”, eg. a cube.
Maya and Rhino are two very different programs, and if you want to learn Rhino, I think it might be a good idea to take a look at the Level 1 and Level 2 manuals and some of the basic videos, so that you can “un-learn” the mesh/polygon based thinking from Maya. It’s my impression that Maya is very much polygon based with some Nurbs tools. Rhino is, in my opinion, the other way around; Nurbs based with some mesh tools (but the mesh tools are getting stronger and stronger). And then there’s Sub-d, which is somewhere in between the two, but in Rhino, the Sub-d can be converted to Nurbs surfaces if needed.
HTH, Jakob


Watch this

You are not using Maya. It would help to stop looking for the maya tools here.

in Rhino :
a group of surfaces joined are a polysurface.
Polysurfaces can be open (two or more surfaces joined at the edges) or closed (like a cube, or capped cylinder)
Surfaces are always 4 sided, however an edge can be collapsed to a singularity, creating a triangle shape.
surfaces can be trimmed or untrimmed.

polygons are triangles, quads or ngons and behave and are manipulated differently than meshes.

1 Like

Thanks for the explanation I understand the differences btwn nurbs and polygons - if you have actually read what I wrote you will see that. your explanation of polysurfaces are helpful but the term polysurface doesnt have any application in this case. the distinction in modeling category in the end is still polygon, nurbs or subD modeling as they are the only modeling algorithms available these days in most 3d application. Those who say unlearn one software to learn another is not really understanding the principle of 3d modeling. the building blocks of modeling are points (vertices) edges (isopam) faces (surfaces). whatever name you give it the principle is still the same. I m learning rhino as someone who is familiar with Maya - just like someone learning English who already spoke another language who learn from translation. Are you saying someone who is learning another language needs to UNLEARN their native language? That makes no sense at all - it is something only a purist who say but purists have a one track mind. When one learn a new 3d software with the basis of another it is just an exercise to find the alternative way to achieve the same. I ask these questions on this platform to find an alternative way - not to get into this theoretical argument about whether learning a new software means you have you “UNINSTALL” the previous software in you BRAIN. before you learn the new one. That whole argument is unhelpful and off putting to say the least.

Dude… I’m out.


Kyle so you are saying that Rhino’s modeling is not nurbs, polygon, or subD based algorithm? It is something entirely new??

Well you know after 20, 25 years of seeing people having trouble learning Rhino because they’re trying to impose the workflow they know from some other software on it, we’re pretty well experienced with this phenomenon, yes.

It’s not just that Rhino is NURBS, that Rhino is “CAD,” not “3D graphics.” And your I-know-everything-about-3D-and-you-are-all-wrong attitude means that the only people who are going to help you here are the tiny handful getting paid to, so good luck kid.


Poly = many

polysurface = many surfaces
open poly surface = many surfaces that are not closed
closed poly surface = many surfaces that enclose a volume.

If that is not clear check out this doc-

Chapter 3 is a very detailed explanation.

fwiw, you are clearly new here… this is a super collegial, super helpful group.
Kindness will always be returned with kindness, usually 10x.

However, Rudeness and attitude will get you banned very very quickly, please act accordingly.