Martin,
Yes that’s a perfectly reasonable comment, although personally I have no need to do complex technical drawings in 3D.
In the absence of an affordable Mac package that I liked, I kept my old DOS PC specifically to run an old version of Autocad … which provides vector based 2D plus extrusion. The free version of DraftSight looks like a viable replacement, which is why I started this thread with a “thank you” to those who suggested it.
For 3D visualisation [as opposed to “proper” engineering drawing], I find SketchUp very useful.
… We bought the Pro version, which includes some clever tools for intersecting shapes.
There is also a SketchyPhysics plug-in available , which allows objects to interact dynamically. [SP is tricky to work with, but I think it’s worth the effort]. … I am currently trying to model gear trains and ratchets.
Moore’s Law may prove me wrong in due course, but I doubt if I could ever afford the processing power required to run dynamic 3D models without relying upon polygons!
MichaelG.