alt Hacker NewsYeah I hate messing with STLs for that reason. It's an output format. Similar to when you make an image in Photoshop with a load of layers and then export to jpeg where it's flattened and all the layer info is lost.
Obj is a bit better but for real design modification you kinda need the original file and the program it was designed in. At least in my experience.
I've never come across STEP though, is that a real design parameter preserving file format?
STEP doesn't preserve all of your design intent (sketches etc.) but it does preserve the geometry (edges, vertexes, faces). So it is a lot easier to work with it because it is lossless and precise. Curves are curves, not quantised/faceted.
So in our image processing analogy, it is still in a sense a "flattened" representation of the layers, but it's a vector format. The best way to think of it is broadly like a 3D SVG, I guess.
https://en.wikipedia.org/wiki/ISO_10303-21
3D printer slicers (except maybe Cura without a paid add-on) can usually load STEP now, but they are still internally meshing before slicing. I think Orca/Bambu/PrusaSlicer all give you some control over that meshing (they all use OpenCascade to do it, in fact).
In FreeCAD you can do things like defeaturing, so if you have a hole in a rounded plate, you can delete the hole, you can delete corner-rounding. You can also break STEP files down to faces and use the surface/curves tool to work on them, or use them as a BaseFeature for a Part Design Body, etc.
This is a pretty useful video for showing the differences:
https://www.youtube.com/watch?v=5l6GOfshigQ