Comment by LiamPowell | Hacker News Reader

Comment by LiamPowell | Hacker News Reader

> can generate fully [...] parametric 3D geometry.

This is obviously a lie without even testing it. STEP files do not have any sort of support for parametric features.

> SGS-1 outputs are accurate and can be edited easily in traditional CAD software.

I tested this on their own demo file to give it its best chance at working correctly and this claim they've made is just a complete lie. I've included the input and output for comparison below next to a correct part I modelled myself[1][2] and a list of errors. These aren't just incorrect dimensions but broken features that make these very hard to edit.

I don't know why they'd lie about this and them provide a demo the shows they're lying with their own input files, and even text on their own page which makes a claim that can not be true based solely on the information further down that page. Is it to get news headlines? Do they want to sell this to people that don't know any better? Is this simply just another case of CS people thinking they've solved a problem without having any domain knowledge to know their claims are nonsense?

- Every dimension is wrong aside from the one that I corrected to get the same scale (there doesn't appear to be any correct relative to each-other which is why I just picked one at random)

- One hole doesn't go all the way through

- The closest hole isn't round (it's two holes with slightly different diameters that overlap with a sum larger than either hole)

- The fillets are not fillets

- The top hole is offset

- The front chamfer goes down past the base

- The not-fillets don't have the same radius

- The two top holes are offset from each other in Z

- The front chamfer is joined to the circle in different ways on each side (to be fair the drawing is nonsensical here, I just went for a tangent with the circle on my part)

- Much more that I've probably missed

[1]: https://files.catbox.moe/mzb9bb.png

[2]: https://files.catbox.moe/5xkna1.png

> This is obviously a lie without even testing it. STEP files do not have any sort of support for parametric features.

Yes, this is also confusing me to no end. How can they make such a claim? They even explicitly state that they generate a B-rep (boundary representation) output only, then in their roller example they say "as the output is parametric, dimensions can easily be adjusted." Erm, no? I'd rather model it again with the proper feature history tree and constraints instead of fiddling with a step file.

I think the point they are making us that the intermediate representation the model works with is parametric and then converted to step for use with other tooling, I could be wrong, but I understand the argument both ways of their solution enables editing of that parametric version before conversion out.

You seem to know what you're talking about. I am completely ignorant of this field, but I have been hearing about https://zoo.dev/design-studio (nee. "kitty cad") for a while because I follow one of the lead devs and it seems like it offers similar features.

I would be very interested to get a comparison from someone who understands the terrain.

Pure text to CAD doesn't seem particularly useful because of how hard it would be to express all constraints in text. Perhaps it's is useful for some kind of mock-up work but that's not really my area.

I agree, text-to-mesh makes much more sense for 3D artist than for CAD. If I'd wanted to have all my parts in text, I'd just use OpenSCAD, writing this down in prose sounds horrible.

And lo, OpenSCAD is great, but is basically unused in the professional world... mainly because textual representation of models amounting to anything more complex than basic 3d shapes slapped together is difficult to achieve. You just can't do so many things in OpenSCAD that you need once you start doing professional designn

Great until you want to fillet or chamfer a complex edge, which professionals do all day long

I really appreciate OpenSCAD. It’s my go-to whenever I need to quickly define a basic shape to 3D print. Unfortunately I predictably hit a wall every time the complexity increases beyond the basics.

The kernel is not robust to the stupid things I naively ask it to do. Often my code makes sense to me, but OpenSCAD refuses to create an object.

Performance falls off a cliff. You can work around it by pausing previews and adjusting resolution, but that’s a big UX compromise.

Still, I’ve tried a few other options and keep cycling back to OpenSCAD. The barrier to entry is very low, coding AI does a pretty good job, and there’s a decent ecosystem of community modules.

I also religiously use OpenSCAD for hobbyist stuff. For making some simple component/replacement stand or enclosure in my house, it's fantastic, don't need the full on parametric modeller for that, plus it's way more modular and extensible with code

This is also why SQL is cursed for LLMs. For queries that are actually valuable to the business we tend to have more constraints than these models can tolerate.

By the time you get done explaining the meaning of your schema, you might have run out of context. Not that it would matter either way. I've never seen the attention mechanism lock onto more than ~10 hard constraints at a time.

Maybe you need to approach SQL the way code generation must be approached: don’t develop the whole statement or script at once, instead put together a plan and execute it step-by-step.

Not everything must be done via LLMs themselves. You could use one or more tools to help generate parts of the query.

You might be interested in this:

https://www.pedronasc.com/articles/lessons-building-ai-data-...

Though it's possible that generating the STEP first is easier to do, and that the plan could be backporting the feature tree using another method / model would then enable editing.

Yes, it would seem post hoc feature tree requires the constraints that come from context in your head, but I could imagine that for most cases a "drafter's intuition" in AI may be sufficient, and you could build an interface to allow that to be mostly given up front and then through iterate post generation.

I could imagine the stepwise approach may allow AI training to be more constrained / efficient that trying to do the whole thing in one go.

Right. If you can express the constraints in text, why wouldn't you just draw it in a CAD program?

Yes, it is a bunch of lies. I wonder what who they pretend to deceive? May be investors?

I’m not deeply familiar with these formats, but isn’t a defining feature of STEP files that they store “B-rep” (boundary representation) data, unlike eg the polygons in an STL file, which are the geometric relationships between surfaces and can be easily used by a parametric editor? That seems to be the point they are making, vs other 3D generation models that output polygons.

STEP files do store higher level geometry data than STLs, making it possible to accurately modify the imported data in parametric modeling software like Fusion, so in that sense they’re “parametric compatible”? They don’t store the design history or intermediate setup, though, so you can’t “go back in time” and change a parameter that was set during the design of the part, and have everything recalculate to accommodate this.

I agree that STEP files are not parametric. But for cases where thats all you've got, Altair Inspire is pretty good at letting you use them in a CAD system:

https://altair.com/inspire

It identifies features as such even from step.

Even simpler tools like Solid Edge in synchronous mode will do a decent job of editing STEP files, as long as they're not just full of polygons.

Yes, but is it even saving you any time, then? For complicated parts, maybe, but the example above is not complicated and the AI is already doing a pretty terrible job. Someone familiar with CAD is able to quickly do this in 15min or so, and then you have all the history and constraints to adapt the design simply by just changing parameters. I'm pretty sure I'd spent much more time fiddling with a rough approximation in the form of a step file.

AI news lying about their real capabilities?

I bet somebody in the comments will also say it works for them and then provide vague or not details at all.

For parametric what the mean is that it generates fusion360 solids that fit into a parametric workflow (unlike say a mesh)

Remember Adept?

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