From AI model to native feature tree in FreeCAD or Fusion 360

STEP is the universal exchange format, but it has a well-known limit: it carries the final solid, not the story of how it was built. Import a STEP into FreeCAD or Fusion 360 and you get one frozen body — no sketches to edit, no dimensions to change, no feature history. For quick edits that is fine. For real rework it hurts.

What a feature tree gives you

A native feature tree is the sequence your CAD package understands: sketch, pad, pocket, hole, fillet. With the tree, changing a bracket’s hole pattern is a two-click edit to a sketch dimension — the rest of the model rebuilds around it. Without it, you are patching solid geometry by hand.

How AiCadGen exports one

Because AiCadGen builds parts as parametric code rather than raw meshes, it can replay a part’s construction history as a native script: a FreeCAD Python script that rebuilds the part as a PartDesign tree, or a Fusion 360 script that does the same via its API. You run the script in your CAD package and get a fully editable native model — as if you had modelled it there.

This only works because the source is a parametric solid. A mesh (from photogrammetry or a mesh-based generator) has no features to replay — which is one more reason to prefer B-Rep solids for mechanical work.

When to use which export

• •Sending to a machinist or another CAD user? → STEP (AP242).
• •Continuing serious design work yourself in FreeCAD/Fusion? → feature-tree script.
• •Printing it? → STL/3MF straight away; no tree needed.

A note on fidelity

Feature replay is faithful for the operations the target package supports natively. Exotic constructions may come across as a base solid plus features — still editable, just with a shallower tree. Check the rebuilt model against the STEP before committing serious work to it.