Triangulating a SubD surface into equal panels with Grasshopper

[sweezy_AFK]

Hi everyone,

I have a freeform shape created using SubD in Rhino, and I need to panel it into equal triangular panels using Grasshopper.

I’ve tried using Paneling Tools, but I’m running into issues: some points are displayed incorrectly, and the triangulation becomes inconsistent in certain areas of the surface.

My main goal is to get a clean and correct triangulation so that I can accurately understand how many panels will be required for this shape.

Could you please advise on a better workflow or tools for triangulating SubD geometry in Grasshopper?
Any tips, examples, or recommendations would be greatly appreciated.

Thanks in advance for your help!

Test1.3dm (82.3 KB)

[Jakob_v_Schirmeister (Jakob von Schirmeister)]

have you tried the quadremesher?

[Tom_Newsom]

The simple answer is SubD → Mesh → Triangulate.

But this only lets you divide things up by powers of two (here it’s 2² so 4 panels per quad patch) and your panels will be considerably bigger on big patches.

Your reference building - the robotics museum in Seoul, has similar topology (quad sphere) to your model (one additional split line) but has a much more regular shape, hence the much more regular panelling.

Their panelisation is a bit more nuanced than these simple Iso Curves, but you can see the valence-3 vertices where the quad patches meet.

Having said all that, I would stay away from SubD if you’re going to use Grasshopper. The tools are incredibly limited. This isn’t a super sculptural/organic shape (SubD’s strong point) so can easily be rebuilt with Surfaces, which have much more robust tools for subdivision.

[maje90 (Riccardo Majewski)]

@sweezy_AFK

equal triangular panels

What do you mean with that?

If you plan to use a single triangular shape, by tiling it you’ll be limited to make a flat or regular shape… not any generic smooth shape.

[Volker_Rakow]

That’s a cool building. It has very strong Wall-e vibes to it. I wonder what the stuff on the top is. Is it a lightning diverter?

[sweezy_AFK]

Many large offices such as Zaha Hadid Architects, BIG, and similar practices often use SubD geometry at the concept design stage to quickly explore complex freeform shapes.

My question is: what are the typical next steps after the SubD concept is approved?

How is this geometry usually optimized, rationalized, and translated into a form suitable for further design development, analysis, and documentation?

More specifically:

• Do you typically convert SubD to NURBS, mesh, or rebuild the geometry from scratch?

• How is geometric control and accuracy achieved after the conceptual SubD phase?

• What role does Grasshopper play in this transition (panelization, structural logic, rational surfaces, etc.)?

I’m trying to understand a realistic professional workflow from conceptual SubD modeling to a buildable and well-controlled geometry.

[sweezy_AFK]

It is necessary to adapt complex forms to the implementation in life, for this it is best to use standard details.

[sweezy_AFK]

In my workflow, SubD geometry works very well — it translates cleanly to Revit and other BIM tools, so I’m comfortable using SubD beyond the pure concept stage.

However, I’m currently trying to understand the best approach to retopologizing a SubD form into a system of equal panels.

The main challenge is not just visualization, but creating a consistent panel layout that allows me to:

• understand the number of panels required,

• keep panels as uniform as possible,

• and maintain good geometric logic for further development.

I’m interested in workflows such as:

• Quad / triangle-based retopology driven by Grasshopper

• Panelization strategies that respect curvature and topology

• Whether this is typically done on SubD directly, or via mesh / rebuilt logic

How is this problem usually approached in professional architectural practice?
Any recommended tools, plugins, or strategies for achieving controlled, equal-panel retopology would be greatly appreciated.

[maje90 (Riccardo Majewski)]

@sweezy_AFK

retopologizing a SubD form into a system of equal panels.

Sorry for focusing on this, but … are you asking a way to obtain a single quadrilateral/triangular panel to tile your whole shape? That’s not possible.

Even for a perfectly revolved profile:

you’ll need an unique quadrilateral module for each row.
If you split quadrilaterals into triangles, you’ll get double the amount of unique modules.
If you have top-bottom symmetry (like a regular thorus) you can re-use half the modules.

If this is irrelevant for your post, then excuse me and ignore my post.

[sweezy_AFK]

what you are talking about is already a step towards the desired result. Even if there are as many standard parts as possible, it’s already good. Can I find out more about how you did this retopology?

[Tom_Newsom]

The trouble with SubDs is this:

That is every component that Grasshopper has for operating on SubDs. You can’t move their vertices, you can’t break out individual patches, you can’t evaluate them at UV coords, you can’t measure their volume or area etc etc. If you want to subdivide, panelise etc. with any kind of control, then you must translate to Surface world.

Now, you can convert SubDs to Surfaces, with good accuracy and a 1:1 patch:surface translation.

But this is only convenient for “friendly” SubDs like this 24-patch cube, which translates to 24 nice orderly surfaces. Something only a bit more complex will result in more surfaces than patches, and new T-junction vertices that you can’t control. Here I just collapse three of that cube’s vertices, to form some triangular patches:

Now I have to tease out which patch is which in this long list, which is at danger of changing as I manipulate the SubD.

I don’t work for Hadid, but I strongly suspect their next step after the SubD concept model is to bake the geometry to Surfaces and then refine/remodel as required. Then they can use the wide array of Surface tools (and tutorials!) to subdivide, panelise etc.

[sweezy_AFK]

Very helpful advice, thank you! I’m trying to understand the process of transition of the concept to further stages of implementation using the example of Hadid. But I think a lot of people use subds or other sculpting methods.

[maje90 (Riccardo Majewski)]

I have little experience in this field, but I guess it depends case by case.
The manufacturing process is the main factor determining how you can do stuff, imo.
You can sure make a random shape in the “early design”, but it’s best to start talking with the production guys and implement their limits as soon as possible.

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For example:
https://discourse.mcneel.com/t/real-life-product-design-examples-made-in-rhino/60157/522

The original shape was a SubD here, and it was actually used later. (tough every panel was rebuilt to make it manageable properly with grasshopper).
The final real-life structure and topology is identical of what was the initial SubD design.

But in this case almost every single panel was “calendered” , bent. Few flat panels. Even less identical modules. Almost every module is unique.

But for this case the panels topology was “easy” because I did know the manufacturer could and would create any kind of panel, they aimed to achieve the best visual outcome without compromises.
… and this led to a very complex planning and manufacturing.

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If you can’t have bend modules, and you are searching to re-use as much modules as possible… then, as Tom said, SubD might not the easiest path.
You will be limited to simpler shapes, but also simpler planning and manufacturing.

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Back to your original question:
you can use SubDs, but to make things simpler try to make your shape with a topology what will result in a single surface once converted to Brep:
(as Tom said, avoid valence-3 vertices)

You can later subdivide it and use only the quad elements as frames (you have to triangulate them).
This is little different from working with a simple periodic nurbs surface degree 3, but it’s somehow easier to insert isocurve divisions and keep the topology as you like.

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This is not my field, so take everything I said lightly.

[sweezy_AFK]

Thanks a lot for the tips!