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by lagrange77 37 days ago
> 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.
2 comments
SchemaLoad 37 days ago
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.
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plumeria 37 days ago
It could be used as pseudo-code for LLMs to produce specific CAD commands?
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martinpw 37 days ago
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.

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plumeria 36 days ago
ideally, fillets are the last operations in the sequence. could the sequence of operations follow a topological ordering that makes it kernel independent?
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SchemaLoad 37 days ago
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.
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itishappy 37 days ago
Nothing stops you from storing a history of mesh operations. This is exactly what modifiers (including geometry nodes) do in Blender today.
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