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What if I tend to import STLs from thing verse and modify them?

IIRC STLs are triangular meshes. Would bRep programs like build123d able to "convert" them to "true geometric objects"?

I would presume the answer is no.

Conversely, what if I want to import STEP files and modify them?

You can make an almost perfect analogy with raster and vector image formats. They both have their niches; however: it's trivial to rasterize a vector drawing, but it's a ton of work to vectorize an raster image well.

So, all things being equal, it makes sense to start your designs at the 'high ground'.

> Conversely, what if I want to import STEP files and modify them?

Right. OpenSCAD can import and mesh STEP files. But the process throws away the true geometry.

I agree that the raster/vector analogy is strong!

bRep apps can handle and work with meshes (though it's probably not the most efficient way to work with them) but no, generally speaking extracting the real geometry requires redrawing them. You can get a long way by decimating meshes and using various tools but you're going to end up breaking the result down and partly redrawing.

Plasticity (the sorta-CAD-sorta-modeller app) has seemingly just added some logic to the recent version to help with extracting the true geometry from meshes. I want to like Plasticity but it's not enough CAD for me right now.

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