ruststep VS CascadeStudio

OCCT is definitely difficult.

I am almost as far as you can get from an expert but:

For example the TNP issue derives from OCCT (or something in the stack close to it, I am not exactly sure) not really handling face naming at all.

So if you want to avoid topological naming issues (which is a hard problem in CAD), you apparently have to do some work to track before and after and reconstruct your face naming.

https://wiki.freecad.org/Topological_naming_problem

https://forum.freecad.org/viewtopic.php?t=27278

Then there are various fairly entrenched issues to do with filleting and chamfering. Basically, both these operations will fail (in FreeCAD at least, but it's OCCT at "fault") if a chamfer or fillet would completely consume an existing edge. (It also sometimes creates impossible objects when filleting, or used to).

Booleans can be slow.

And more generally, it seems if you track the FreeCAD project that OCCT can be inscrutable when things fail; error messages aren't the greatest etc.

The flip side of OpenCascade is that it seems to be highly portable and has for example been compiled to JS with Emscripten for this astonishing thing:

https://zalo.github.io/CascadeStudio/

It's a monumental open source project, for sure, and it's definitely not nothing that we have an open source CAD kernel; these are projects that perhaps have to extend beyond the working life of an individual developer if they are to be stable. And there are loads of projects built around it.

If you haven't seen it you may want to check out https://github.com/zalo/CascadeStudio

From what I see, it is exposing the OpenCascade base commands directly, versus your completely new DSL, but you might be interested in a way to implement your DSL on top of such an interface such as this which takes out a lot of the extra work of having a rendering interface, exports, etc, maybe.

It's nowhere near ready for primetime, but you should take a look at CascadeStudio (https://github.com/zalo/CascadeStudio)

FreeCAD is GUI-based though, not code-first like Fornjot. A better comparison would be CadQuery (https://cadquery.readthedocs.io/en/latest/intro.html) or Cascade Studio (https://zalo.github.io/CascadeStudio/), both of which are code-first and based on the same CAD kernel as FreeCAD.

It is an actual example from CascadeStudio, but I haven't looked into it enough to know how what actually happens under the hood, but I assume the following: