Cartesian – AI 3D Modeling for Design | Hacker News Reader

Cartesian – AI 3D Modeling for Design

formas.ai

116 pointseustoria81 comments

I'm so excited about this sort of stuff. ForgeCAD [1] for me was the first mind-blowing application of this a few months ago, where I'm able to just have claude (or codex) write JS that creates 3D Models that I can then print in my 3D printer.

- Built a ring for my compost bin that can properly hold down the plastic bag. This was originally a multi week project because I was also learning Fusion 360 in small 2 hour chunks over many weekends, then with ForgeCAD I had a good prototype in 60 mins with multiple iterations.

- I also built a cover for my overheating Logitech Circle doorbell, snapped a photo, gave it to claude, and claude found all the dimensions on Logitech's website, and then we iterated with 3-4 prints until we had it just right.

This is a whole new set of workflows that are unleashed with agents, even for hobbyists.

1: https://forgecad.io

Yeah I was skeptical about AI until I learned (through hands on testing) that an AI can fail 9 times and get it right on the 10th time - in like 1/10th of the time it takes a human to get it right. It's all in the iteration.

Are those not the exact same workflows, just replacing "I spent time learning" with claude?

I find that if you don't skip the learning step, you can then use the tool more efficiently(e.x. you learn to measure twice and verify so you can iterate in 1-2 prints instead of 3-4)

I am not averse to learning (I spent hours learning Sketchup many years ago when redesigning my garage).

But the time freed up not learning Fusion360 freed up time to learn about different kinds of fasteners, clasps, how to arrange magnets, etc, so I moved the learning to a different place.

Plus avoiding the "wife is angry cuz this project I over-engineered has gone on for weeks unsolved" factor is always a nice bonus.

I love to see more of these tools build on rhino's kernel. Arguably the best modelling (parametric, manual, or SDK) ergonomics when it comes to, from my experience, early stage aec workflows. A similar tool launched recently [0] that i found interesting. I'm also biased as it's my first and only true love when it comes to "coding things" for the built environment.

My take was that designing buildings was always the cheap part, and not core to what moves the needle in AEC (architecture, engineering, construction)

[0] https://illoca.com/ , not affiliated

These products are still in their early stages, but it is clear that the AI wave is reaching 3D modeling as well. It will impact mechanical and civil engineering just as it has impacted software development.

3d modeling for use in software (games or similar) imo is fine, but I would love to not see this stuff in civil engineering. People without AI are unable to design buildings that don't collapse (e.g. recent NYC apartment highrise), adding AI into the mix will just make things worse.

hastily adding AI in into the mix will make things worse

its good to be skeptical, better to spur competition and address any limitations to competition functioning quickly

Why do you presume it will make it worse instead of better? Humans, as you point out, could not manage to competently review buildings that don't collapse. Why would adding an additional level of checks (human or AI) do worse than not adding one?

Ai isn't being used to make competent people better but tries to give supposed expertise to people who don't have skill in that area.

I don't think so. As a mechanical engineer, CAD is only half of the design process. The other half is actually building and assembling your design and testing/debugging what you've created. You still need the mechanical knowledge and intuition to take something in the physical world, figure out why it doesn't work, and apply that to the CAD design to improve it. It would be incredible to have AI help me model faster, but there's no validation loop like there is with software, so you can't have an agent run wild and endlessly iterate.

None of the things you list in the "other half" are out of reach for AI.

Also: disagree about the lack of validation loop:

   a) AI can actually build one for you in many cases

   b) if you give agents an actual validation toolkit, you'll be surprised what AI can do

Of course, if you expect to prompt "give me a NURBS model of a complete, working v8 motor" and get a result, then yeah, sure, we're not there yet.

I've actually built a bunch of stuff with a combo of astra, blender, openscad and tiny bits of AI written helpers ... giving the AI the proper "hands" to work with the models is key.

One particularly useful tool to provide the AI with is to be able to "look" at the model as it iterates on it (measure dimensions, shoot arbitrary rays at it that return exact intersections and normals, see if the object obeys engineering constraints, etc ...).

Works pretty well for many, many things and saves a TON of time.

AI cannot physically build anything in the real world, what are you referring to? That's a huge part of mechanical engineering.

And you can give it simulation tools, but those are far far away from accounting for everything in real-world physics. You can simulate very tightly constrained problems, but you can't simulate "assemble this actuator and test it", there are so many more variables in the real world that are not easy to account for in a simulation.

If you aren't an engineer that works on physical products, it's hard to articulate just how far from reality CAD and simulations are.

This is how LLMs have been since the beginning. They can be really okay at the most surface level information, but as soon as you dig any bit beyond that, it all falls apart. Inquire any chatbot about something that you're an expert in and it becomes quickly apparent.

I'm here for using LLMs to take some of the tedium out of product design/mechanical engineering, but I just haven't seen a good proof of concept yet. It always seems to be some variation of "Design a sphere. Oh wow, this is incredible!"

> CAD is only half of the design process

I'm not a mechanical engineer but I would be surprised if it was even 30% of the process. Materials, manufacturability, durability, fitting into other requirements. Some of those things can be part of the CAD design, but there's so much more.

Not to say that CAD isn't a big chunk!

Agreed, it's probably 10% of the total product development process, but approximately half if you're just considering "design" tasks.

> As a mechanical engineer, CAD is only half of the design process.

Same thing can be said about animation and games.

Was there a product demo in here somewhere that I missed? This seems like a wish list, not reality.

I've been using Astra to just create things in Blender. It's great.

Kill the scroll jacking. It's a sign you're on Windows.

Exactly. I just give Astra an image such as furniture, and it creates an 3D reproduction in Blender. You don’t even need computer use. Codex and Blender’s scripting engine is enough.

Can you do this with the 20 dollar plan?

Yes, but it eats your 5-hour quota really quick.

I have an example here. Took 3 hours with Pro Plan.

https://simulationcorner.net/chair/chair-evolution.gif

That's cool as hell.

CAD is a different beast than mesh modeling. For product design you need a parametric model that can have precise dimensions and is constructed mathematically step by step. Mesh modeling is just moving a pile of triangles around in a very imprecise way. Works fine for 3D printing or digital assets, but if you want something that can be manufactured that's not good enough. And there isn't a good way to go from STL -> Parametric CAD so there's still room for a product here.

> there isn't a good way to go from STL -> Parametric CAD

yet.

as a matter of fact, you should try what AI can do on that problem, you'd be surprised.

I have tried, I really wish it would be better because CAD is a slog and I want it to be automated. It's pretty bad at real world tasks.

It's just a matter of time. Astra was trained on a new 3D modelling dataset. They will surely train it on CAD apps (if they have not already done so). I don't hold out much hope for competitors hoping to get in front of that train.

Astra can use build123d, too. You'll get a STEP out of that.

I've tried Sol on build123d and it was completely unusable, I should take another stab with Astra though.

I had a similar experience, but it worked just well enough that I wanted to try my own similar experiment, but using a functional API in Elixir and giving the agent some introspection tools. I'm very much a novice to this space and learning as I go, but I've been able to make some interesting projects with the library so far, which is all I really want to do: https://smith.hexdocs.pm

If you want to build by hand, there is a Kino renderer to build your projects interactively in Livebook, which is actually surprisingly helpful for learning.

CATIA has had mesh import with canonical feature detection, and automatic replacement with parametric part features, for at least 25 years. It's in the "Quick Surface Reconstruction" and "Basic Surface Recognition" tools. They even work sometimes.

https://3dswym.3dexperience.3ds.com/wiki/catia-user-communit...

https://resources.rand3d.com/insights-from-within/scanned-da...

Unfortunately the P3 license costs like $15k per year, and it is f'in ugly clunky software.

I was able to have Astra accurately solid model with plasticity (NOT import from Blender) and presumably it would be trivial with autocad, but I haven’t tried it yet.

I suppose you might be able to force a Blender agent to do parametric modeling via geometry nodes. It would be a horrible, kludgy, slow workflow for a human, but the AI won't complain.

The only way to go from STL to BREP is through decompilation style recovery/reconstruction, because of the semantic information loss, so it's a task that can only be done via LLMs or human CAD users. Essentially, they pretty much have to remake the model from scratch using the STL as a reference to make the CAD. There really isn't a good way to automate this without machine learning/LLMs.

Fusion 360 can convert many STLs to BREP automatically. It can be slow and error prone but it does work. It will recognize large regularly curved areas and replace thousands of triangles with a single smooth curve.

" if you want something that can be manufactured that's not good enough"

People design all sort of buildable things in SketchUp and it's just about dragging polygons around.

You _may_ need accurate surface if you run your model to CAM.

But to this day lot of manufacturing is still done via drawings and there the only thing that matters is that can you draw some type of lines and attach clear dimensions to them. So the shapes don't necessarily need to be accurate for all flows since they are more like topological hints to the person reading the drawing rather than accurate replica of the thing to manufacture.

I've had decent success getting Claude Opus to design models using the python cadquery library, and then I can import the step file to fusion 360 to make any changes I want afterwards.

I gave some very bad sketch made in jspaint to Astra, plus some text instructions, and I got back some clean STL file and a beautiful 3D render.

It even made a second STL file with the same model rotated for 3D printing.

I remember all those hours on SolidWorks many years ago, and now you can just speak and present bad drawings to the computer, and it does it okay.

Are you hooking it up to blender via some MCP or are you just creating files and opening in blender?

From my experience trying to build parametric CAD modeling using FluidCAD [1] using its MCP, the biggest breakthrough is ASTRA. It seems to work well actually with any CAD if it has ways to verify its output. No otjer models was able to match its accuracy even Fable.

[1] https://fluidcad.io

i can't even read the website because you're animating the background, why would i trust you with architecture?

Being able to draw what you can describe, or steal from prior art, isn’t a solution to real world challenges. The hard part is coming up with novel design solutions.

On top of this good design requires control of every line and curve (G2, G3, radius?)

The things these tools do for you and don’t allow you to easily control ruin their work.

If you do manually edit the output for precision they aren’t actually providing any value.

They are the drafting equivalent of clip art.

Minecraft style designs work but complexed geometry yields presentation quality in a triangular hell, which is and has been the problem with all Ai CAD since day 1. What Ai is good at in CAD is finding applicable formulas but anything functioning in a civil space is a nightmare on wax. There's not even enough correct Ai in sensory to make it reliable for self-driving cars and now they want to make the car itself with Ai? I guess in for a penny...

GPT-6 Astra with computer use has gotten some of architects and 3d modelers wondering what their future is. Astra does such a good work with SketchUp 2026 and computer use, here is video, but it is well worth it because the author actually knows his stuff:

https://www.youtube.com/watch?v=E-ECbD14g_8

The video game applications are truly pretty cool ... though I don't know who would admit to using such a tool in the current environment.

Some of the other things like the `Residential`, `Structure and Complex Shape`, and `Large Scale` seem like they'd need review by engineers to be useful in real world scenarios? Do architects just sketch whatever looks good as a first pass?

Wow this is some advanced stuff re: Cartesian by Formas.ai folks. I downloaded their STL and 3DM, the definition and fidelity is just wow. Looks like lots of hard work to get here. Super keen to follow this. Giving creds where creds deserve!! If formas is reading this, kudos and great work!!

Shameless plug for Cordyceps, my MCP server for rhino / grasshopper. Works great, I’m building molds and props and all sorts of stuff: https://github.com/brookstalley/cordyceps

"Architecture and product design" but no STEP/IGES/BRep output, just triangles?

Actually this appears to output 3DM, which is the CAD format Rhinoceros 3D uses, and is based on openNURBs. The typically tiny Claude (?) text (such as I can read it) makes it clear it's not just a mesh format, mentions faces and edges.

On that basis it is a step up from the usual AI CAD silliness.

"no STEP/IGES/BRep output"

SketchUp does not really have that either if you are expecting something else than triangles. Since sketchup has polygons you could argue they are brep but even then only accidentally.

Architecture works with a bit different ruleset than mechanical cad.

I love the web design though! Formas.ai has been doing great work in the visualization space, and it’s great watching them tackle 3D via the very apt name Cartesian. Defo support what they are doing. Maybe I can finally sleep better too!

Is the site owners are here: that background and scroll effect is terrible.

Came to the comments to say something similar.

Indeed — I try to stay away from website design critique here and it's against a rule, but that dot field makes it actually impossible for me to read, especially given the low text contrast and small fonts on the body text.

I usually kind of roll my eyes when people complain about visual effects on a website but I wholeheartedly agree. It makes it very difficult to read

adding representation to the silent non-bothered audience, I like the scroll effect here and don't find it terrible

Looking at a bunch of these: I don't think they are even manufacturable. This is something you would use in a video game.

You are right to push back on that.

> This is something you would use in a video game.

You say it like it's a bad thing.

They're saying it as if it were contrary to what's being claimed. The tagline says "for architecture and product design." The supported file formats are not video game formats.

It is when the tool's tagline is literally:

> an AI 3D modeling tool for architecture and product design.

Can it work from technical drawings?

Like, I give it a datasheet containing a number of projections and the tool produces a correct model with the proper dimensions?

You can already do that with GPT Astra. Having LLMs use UI manually is very expensive on the token side though.

What is the success rate?

Very high with the correct tooling. Vision tends to be the worst reasoning mode for LLMs compared to code, which is why I rely on a code-first approach for my own software stack. Essentially, they need to have a way to keep part of the drawing in focus to avoid getting distracted by the dimensions they don't need in their vision.

https://github.com/yuechen-li-dev/Aetheris/blob/master/sampl...

The initial dimensions of this phone were one-shot by Codex Astra from the publicly available 2D drawing, and we spent another turn implementing the G2 continuous fillet blend surface for that particular camera bump. If you have a STEP viewer, you can check the dimensions against that phone company's drawings which was posted on HN with their other products yesterday I think, and all of them should match exactly down to the drawing tolerances.

It really depends on the complexity of the model you are trying to generate and the budget you have.

These all seem backwards.

I like to think in shapes. I like to draw and sketch, as that has the lowest barriers between the mental concepts and physical ones.

I do not like to use cad software. It is painful to express ideas with it. Also same for all kinds of drawing software. It's just very cumbersome.

I hate explaining spatial or shape concepts to people with words. I hate having them explained to me in words.

A photographer doesn't explain his work, he shows photos he has taken.

Adrian Newey used to work with pen and paper while others had been using CAD for a long time, and won F1 championships.

Can we now make the computers less clunky and less about typing or hunting with the mouse. We want low friction to express ideas.

This seems the opposite. You're not expressing your idea, you're asking for the computer's idea.

Couldn't agree more. The first thing we get ends up setting the direction before we've even figured out what we want.

Considering the ability of men to aim in urinals, Cornucopia is really one of the worst idea.

The moving dotted background makes it impossible to read anything..

My thought exactly. What a terrible background!

oh my... for me its sure way to induce motion sickness...

I've just started working on 3D modeling software of my own, though this looks to be far ahead. Mostly focused on 3D printing - creating printable models is pretty expensive and tedious at the moment, and fully native.

[1] https://tomasimodeler.com (pardon the AI-slop, it's just a placeholder)

    Yours stays yours.
    What you keep is never redrawn. What clashes is said out loud.

    It understands.
    What you mean, how things relate, what must not move.

Pure uncut nonsense

"What you keep is never redrawn. What clashes is said out loud."

I keep seeing people in this thread lamenting that "There is no good way for LLMs to design/generate parametric STEP models yet", while I've spent the past 6 months working on this exact problem.

So, yesterday, I've had Astra build a moving assembly of Babbage's difference engine with it with 400+ parts and real parametric geometry, and you can also download the full STEP model assembly there.

https://aetheris-difference-engine-showcase.yuechenli.worker...

And here's a STEP file that I've had GPT reconstruct of a popular phone with exact parametric dimensions just from the 2D drawing, took like an hour:

https://github.com/yuechen-li-dev/Aetheris/blob/master/sampl...

Completely free and open source, you can use your own Claude/Codex to start vibe-coding and generate perfect STEP file right now.

So, no, it's not a matter of time on "when can AI do CAD", we are already here.

Sorry if I sound a little frustrated and a bit too self-promotion-y, but I just really want people who says "I wish this capability exists sometimes in the future" to know that it already does, and you can use it right now, for free.

this difference engine model has a lot of obvious flaws - the gears do not mesh with each other, the teeth directly overlap. the notches that are supposed to articulate to ratchet aren't actually engaging the teeth on the ratchet. the ratcheting mechanisms on the right are straight up just hovering in the air and are not attached to anything.

that's probably what people are talking about when they say it can't do CAD?

Complex assembly mating is hard to do even in SolidWorks. It's a demonstration model to explain how it works, not a kinematic simulation, turning three.js into a physics engine is beyond the scope of this project.

Is making parts which actually fit in scope?

Because that was what was being criticized, and that seems to be where your project is failing.

Failing is a bit of a strong word, right?

Thank you for your bug report. It is now fixed.

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