I've used Illustrator, not well, but enough for my needs (drawing diagrams for academic papers, mainly). Now I've spent a couple of days messing with Illustrator and learning about anchor points and joining paths. I was having the problem of joining paths but not getting smooth corners.
By zooming in much more I could identify the anchor points I had to delete, selecting them by using the Direct Selection Tool.
But I continued to have problems joining paths and trying to break paths at anchor points. I started drawing the thing again and by trial and error clicking on 'merge' and 'group'. Of course this is the problem with the documentation - I just did this without remembering to take screenshots.
I used hexagons that I merged into the outer outline and added the other shapes (the inner lines and the 'doorway'). I outlined the lines: Path - Outline Stroke. I tweaked the proportion of the top by selecting the top anchor points and moving them all down together with the bottom arrow on the keyboard. I changed the width of the inner diagonal lines by moving their anchor points. Since this moved everything around, I made a new Layer, put the same basic hexagons there, and lined up the anchor points with the background hexagons. I could then hide this layer when I didn't need it. This is a super boring description, but every time I work with Illustrator I find that some steps are better done first and then other steps. So mess and chaos and randomness first and then do the whole darn thing again in a better order.
Now I have a path outline that I can try on the vinyl cutter for the cutting exercise. And a bit more knowledge about Illustrator.
As for the 3D designs, the last time I did anything CAD 3D modelling related was in the 90s when I tried to take a course. I'll play with SketchUp for a while and do something simple. To be continued.
This was really interesting. Notes and reflections to come.