I made this as a wedding gift for my brother, it took a long time as there were 16 double sided strips to machine and it was a nightmare to glue together. It didn’t turn out as well as I hoped due to seams/alignment issues but overall I’m reasonably happy with it. I think I have a much better way to do it if I ever try to make another one.
It is ~14" in diameter and made of Spanish Cedar.
The back of each strip was milled with a 1/4" ball end mill and the front a 2mm ball end mill.
I wrote some software to generate the g-code and in theory you could use this method to make a sphere of any size.
Unfortunately the software is a bit of a mess as I just wrote it quickly for this project, there are a bunch of hard-coded parameters specific to the stock I was using. I am planning on cleaning it up and including it as one of the templates in a CAM tool I am in the process writing.
As stated, the front was milled with a 2mm ball end mil.
Sorry, I didn’t realize your question was about the generation. The software I wrote creates both the back and front sides. The front is based on a heightmap, for this project I used the NASA ones from here: https://visibleearth.nasa.gov/view.php?id=73934