Bridge 2 Subd with different edge count

I totally agree @hifred clean quad mesh geometry will make clean subd geometry in Rhino as in mesh based modelers. We’ll try to make sure all the editing tools needed to clean up meshes or existing subd are available and you’re right, this will be a new area in which to educate users. The QuadRemesh tool is something that may help some users in some cases create cleaner geometry but indeed it is not going to solve all possible issues. Knowledge is still important.

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You can give the ToSubd command a try now on single srfs or use the subd output option on commands like Loft or Revolve for instance now in the v7 WIP. For trimmed srfs, try QuadRemesh on it to make an all quad mesh version of it and convert to subd in one step. This may help if you are trying to convert a polysrf with trimmed srfs to subd.

Hi Brian,
my posts contained some feature requests – could you please add them to the list?

  1. Use SubD-Cage instead of a classic Rhino render mesh (obviously at higher SubD-Levels) for viewport display (➜ of SubD-objects)
  2. Use the same mesh for unwrapping (user may choose the viewport displayed SubD-Level on the flattened mesh but edits the vertices of the unsubdivided cage).

Doing UVs that way would have great advantages over UVs on surface models: Any topology-changes would immediately get reflected in the UVs – one therefore could start working on materials and mapping while still developing the model (whereas one with Nurbs models has to start UVing from scratch, upon model changes / surface replacement.

Yeah, these tools are super impressive – but they are rarely able to create cages for manual modeling. Output is too Hi Res and often topology-wise not ideal for further manipulation. Run on a patch within an existing model, a remesher would need a lot of context information – what’s the structure of the adjacent mesh? Zremesher at least (the quad-remesher in Zbrush) is mainly used to improve the quality of texture baking from High Resolution models, not in order to create cages for SubD-Editing.

Good low-res cages for manual modeling imo should rather get created by hand, possibly on top of an existing, ruleless mesh. I find retopology tools which let you create a Low Res network a lot more effective for this particular task.

Thinking of SubD in Rhino and using any combination of imported and converted meshes and surface tools with output=subD and subD-converted Nurbs-patches I see a very tough challenge to make this all play well together. The fundamental idea of SubD – I find – is dropping the so familiar concept of patch based modeling: One rather needs to create a single piece of flesh with a consistent internal structure.

A model which – if it had a Nurbs-equivalent – was made from just one surface.

Here we have one of the classical limitations of SubD: mismatched loop count.

Abraham Maslow once said: “I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.”

…every SubD modeling program out there has had this problem because all they have is a SubD topology: their hammer.

I think this highlights the need to have a blended input/output between various topology types available in Rhino.

I think what makes sense here is that BlendSrf works with history and SubD edge loops as input. So you can make a perfect blend, when you intent is anything except downstream to other CCD apps like Maya/Max/VR pipelines (where you need SubD only, but like Holger pointed out there’s problem here already since Rhino is not using Catmul Clark)

I think one may generalize this sample to what will always happen if two or more SubD patches are created, without information on ‘how to fit things together’.

I think RMA should first encourage box-modeling and poly by poly modeling. These strategies both make it harder to create stuff that doesn’t match – and they teach topology-fundamentals on the fly.

That’s a very small market. More like a waste of time. Especially if you are focusing on people modeling things for design/prototype/build.

There’s also a ton of mature products that do this right now, and every time they tried to enter the design market they hit a brick wall.

I was referring to novices trying to get their feet wet with SubD modelling. Here I think one should stick to proven workflows and can’t find this a waste of time.

I consider this rather a consequence of rigid topology constraints in SubD modelling and not of the chosen approach to build and shape a mesh cage.

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I was too.

I think they are interrelated.

One of the strongest value propositions of Creo and NX’s SubD integration is the fact that you can match and managing continuity between Nurbs and SubD edges. Then you can you make each part based on the topology it needs (or it has, ifs it’s a part you don’t own or control) and properly bridge between them.





I think I understand what you are after, Gustavo and I’m not against it. I just don’t see any of this coming to Rhino in near future. Right now Rhino can not even maintain upright continuity-conditions between a set of surfaces while manipulating them. The highly expensive tools you mention had these capabilities on Nurbs geometry for many years – long before one finally made them available inside a hybrid Nurbs-SubD workspace.

But hey – even if I was wrong and such solvers would come tomorrow – I think it made sense to first teach some SubD-basics, to those who are about to get their feet wet with a new modeling paradigm.

Thanks for the feedback on texture mapping. I also hope unwrapping subd will work that way. I have filed regarding the inability to unwrap subd currently. I added your comments there.

If possible, please make a separate topic on the forum here showing a specific issue you’re running into and I’ll make sure the bug or request is filed. Thanks!

I was not referring to own workflow problems, Brian. I think that learning SubD is generally tough for people with a patch by patch Nurbs background (same is true for the other way round) – and I expect that using a Hybrid concept will even cause a higher learning curve. Models made with traditional Catmull Clark SubD methods remain surprisingly deformable as a whole, until the end – they indeed hold a lot of valid shape variants in one workpiece.

Then again such models do require an unexpected degree of topology pre-planning. Combining new elements with existing geometry may turn out as a mayor challenge – one possibly needs to rebuild everything one had so far. I have posted a sample of such a case here, years ago.
Runnie, a fellow user further down that thread took that challenge and he indeed needed to redo the whole topology.

From an educational standpoint though, first looking at traditional Catmull Clark methods is great imo – it makes differences to Nurbs, strong and weak points most obvious.

Working successfully with a hybrid Nurbs+SubD approach would not only require a lot of tools which are not yet available in Rhino. One also needs an Editor who already knows well the strengths and weaknesses of both methodologies and who has developed the skill to decide what approach likely works best in a given situation.

This recently posted clip sells some of my points quite well: It’s Author likely has decent Nurbs and some SubD background and he checks out some new (and pretty advanced) SubD tools in Alias with the camera running. It’s actually great, that this clip has quite a few issues:

Features aren’t discoverable, operations do fail. The modeling progress, compared to Maya, Blender or similar seems terribly slow. Distinct differences between modeling principles appear oddly blurred. The result of the modeling session is all bumpy. Now imagine reactions: What do those say, who’ve just begun with Nurbs Modelling? What does the Surfacing master say?

Thanks for the feedback. Please post any specific suggestions you have, after working with subd in the Rhino 7 WIP, in a separate topic here on the forum. Minimizing the post to a single issue or request is always best too. This makes it easiest to convey the info and opinions to our developers who are actively working on these tools. I’ll do my best to boil down your larger concerns here into individual actionable reports as well. Thanks again.

That behavior changed recently to produce merged faces instead of a gap. See if you can update your v7 WIP.

Yup. Now works here too.

You can take a look at this guide for transitions, I would also like to have match compatible between nurbs and sub-d like T-Splines had, but in the meantime this definitely helps.

Polygon Table


RH-50789 is fixed in the latest WIP

RH-50789 is about SubD having a texture mapping icon but currently only primitive styles such as box or planar are supported. Unwrap support is filed as

RH-54604 is fixed in the latest WIP