[knollimar]

It says "can convert cad latents into a sequence of parametric CAD commands"

Which CAD program? I'm confused

Am I reading this right?

>Most importantly, GenCAD does not merely generate a 3D solid but also the entire CAD program.

[hug]

It's DeepCAD* output, it looks like, which is a JSON payload that is the sketch / extrude / whatever steps, which is itself based on Onshape output.

Looks like you can go JSON -> step files, but not really in such a way that you can modify any of the operations.

* https://github.com/mightyhorst/DeepCAD

[dbcurtis]

> Which CAD program? I'm confused

Clue here: > Our proposed GenCAD architecture...

So, at this point, it seems like this will work with all CAD programs, since they have yet to encounter any systems that they can't work with. More seriously, my guess would be whatever one is available for free in their lab. Kind of standard operating procedure for academic projects -- do a proof of concept, make a video that avoids known bugs, get a grade, push source to git, graduate. Good ideas come out of that... production code... eh... maybe.

More likely someone ends up in the situation that my kid did, previous graduate student's git repo is stale by 2 versions of C++, and 4 versions of ROS, and neither of the two unit tests still work after porting.

[lagrange77]

> Which CAD program?

Doesn't matter. CAD models/objects are represented by a sequence of operations on a primitive or sketch. Unlike meshes, that describe the manifested resulting shape of objects in 3D programs like Blender.

So it's about the fact, that their model outputs that hierarchy of operations. The history of development, not just the result.

[SchemaLoad]

How does it not matter? Every CAD program is not going to have exactly the same interface and commands. I doubt for example this will for example generate and OpenSCAD text file.

[plumeria]

It could be used as pseudo-code for LLMs to produce specific CAD commands?

[martinpw]

It will still be application dependent.

Code to compute fillets and blends gets incredibly complex when multiple surfaces are involved. And when surfaces are barely intersecting, or almost coincident, all bets are off what the command will do - very much depends on the geometry kernel and the tolerances it uses whether it decides the surfaces even intersect. And if it decides they don't intersect, all downstream commands will fail. Handling tolerances is one of the hardest aspects of CAD. (It's no coincidence that most open source CAD applications always demo with the same relatively basic types of models - they just can't do truly complex CAD.)

So a simple set of operations - cube, sphere, intersect - sure that will work anywhere and will be portable across applications and makes a nice simple demo. But once you start doing any serious CAD modeling the result is kernel dependent. That's why portable CAD formats like STEP do not preserve the commands used to generate the results. And why native CAD application formats do preserve the command history but are not portable across applications.

[plumeria]

ideally, fillets are the last operations in the sequence. could the sequence of operations follow a topological ordering that makes it kernel independent?

[SchemaLoad]

It could be anything which is why the question was asked what it actually outputs. I had a skim through the page and code but couldn't see what the output was.

[itishappy]

Nothing stops you from storing a history of mesh operations. This is exactly what modifiers (including geometry nodes) do in Blender today.