Almost T-Joint/Star-Joint how would you model this?

Hey guys, I’m getting a bit nervous with my deadline. Do you have any idea how to create the joint smoothly in V6? Curve Network doesn’t work and the video in the Rhino blog with star joints doesn’t help much as here are different angles and tube diameters. Thank you so much! Hannes

Not sure if it’s what you’re after but that would be my take on it

Can you provide the file?

@velopi thank you so much for getting your hands on this here is the file

Tankstellenüberdachung Export Rhino Forum.3dm (166.2 KB)

other strategy could be solve the join sequentialy instead of all at once.

1 Like

I think @DiegoKrause 's strategy works well.

Tried to patch things up, but failed…
needed a better plan to get rid of triangular corners…

somethinglikethis.3dm (453.3 KB)

Hej Hannes,

you could maybe try this tutorial for Y-branches, it’s the same principle, no matter if the tubes have the same or a different diameter. Just model the primary domain and then reflect.

Happy branching!


I think that subD is the efficient way for not spending 40 min on Y branch…
Nurbs is used for controlling curve for mechanical constraints and aesthetical purpose in the same time but for aesthetics only, for me subDtoNurbs is the key.
You just need to extract boundary control polygon for starting your sub-D topology

When you know what you’re doing, you can model a Y-branch in a few minutes.

Instead of futzing the model with polygons, I believe the OP will learn many good things about proper curves, good patch layouts and continuity. After all, Rhino is primarily a NURBS modeller.

Polygons are ok for visualisation and prototypical 3D printing, but not for passing on the data to structural engineering and toolmaking software for production, depending on how the product will be moulded or cast.

90% agree for the learning purpose but for machining G2 are enough and at the end you get a nurbs from your subDtonurbs so you can evaluate everything… finally you just have more flexibility for the form finding in your design creation and it’s the most important ! everything beyond is just projection and rebuild…

But if you aim class A for commercializing your nurbs model and not the final product I’m 100% alright with you

Ps i love nurbs but vertex location is prime.

We’ve spend a lot of money/effort for reverse-engineering polygons into surface or solid models, but with no good result, comparing to the time/budget it would have taken to develop the design in surface or solid modelling in the first place.

But probably, the OP just wants a model for rendering or 3D printing at scale, who knows?

Nurbs and subD are just paradigms nurbs can produce bad surface if they are bad modeled too and once you rebuild a projected curv no matter on what kind of support you are: mesh, subD(it’s different) or nurbs, you enter in the one span world.

Just watched full thing…wow! I think I should pursue a career in class A modelling.
So relaxing.

The SubD implementations inside CAD apps are usually not polygon based. Hence you do not get a facetted model. What you see e.g. in Gijs’s screenshot is the control-polygon (cage) which also exists in any super duper surface model.

I still see a lot of issues with Nurbs-compatible SubD for precise, complex models with cutouts and exact dimensions – but for isolated shape-transitions limit surface based SubD should work quite nicely. Did I already say that the result is not polygons? Ah yes, here :o)

Do we need another thread about Nurbs Vs. SubD for production?

I think these 242 responses on this thread cover the topic well:

@lagom, @hifred, stop it! :joy:


Class XYZ… if it looks good, it is good ; ) When a client does not care (very sad) or does not have budget for proper 3D (equally sad), then I would not bother. At the end of the day, you want to be in the pub at 5pm!

Well, the OP came with an interesting NURBS modelling question; then the subject of polygons was introduced ; )

1 Like

Yeah these can wait!

Sign out…see you next door! (pub)

Have a great one everyone!


Here you go Lagom,

All Nurbs, Class-Zy

You got the right spirit - chasing a Guinness with a Stella… stellar ; )