IIRC the FreeCAD solution tends to create names of ever-increasing length as you continue building.
That said, since v1.0, I've had far fewer instances of being affected, and have started doing some direct-on-face features (usually sketches) again.
The geometric kernel is doing boundary representation operations so when you do a boolean or a fillet, it doesn’t “edit” existing faces, it computes an entirely new b-rep from scratch. The old faces, edges, and vertices are gone and new ones are created to replace then. There’s nothing to hang a persistent ID on because the entities themselves are ephemeral.
There are solutions to the problem but they all break down eventually. I think freeCAD uses topological tracing and naming schemes so it encodes a face’s identity by how it was created. e.g., “the face generated by the intersection of extrude_1 and the XY plane.” The problem then is that parameter changes or operation insertions in the history can destroy those too, creating a new feature that can’t be easily mapped to the old ones. That’s where all the heuristics come in.
Unique IDs are used internally, but they only last for the lifetime of one evaluation. The hard part is establishing the equivalence between entities across re-evaluations when the topology itself may have changed.
Although… as others have noted, this is a problem with basically all CAD packages, as on a fundamental level, it depends on user design intent. Just some have enough bandaids that it’s more rare.
I’ve not encountered the same issue in FreeCAD 1.1 (to which I’ve transitioned recently). There are of course other frustrating niggles in FreeCAD, but not this one (yet).
> This problem is not unique to FreeCAD. It is generally present in CAD software, but most other CAD software has heuristics to reduce the impact of the problem on users.
Solidworks and Onshape don’t “hide” it better, their algorithms are better and break down in much more complex models than FreeCAD. Each one also tends to have its own quirks so as you learn to use the software you get a bit of intuition on how to best model certain features to avoid angering the topological naming gods.
I don’t think I’ve ever seen Solidworks break down in a simple model, it’s always been in complex shapes using advanced features.
Fusion 360’s heuristics are so good that I rarely run into these problems. When I do, it’s usually because it was a drastic change to a previous feature in the timeline and I’m expecting to encounter issues because it’s a really fundamental change.
