Here I am answering my own questions.
It seems that you start with a 3d modeling program. I was only aware of Autocad but there are other programs of course. I saw “Blender” mentioned in other threads and found this:
If there is other better starting points, I am happy for comments (and links)
(Mac OS 10)
- This reply was modified 6 years, 7 months ago by Bippa1.