If you look at proper drawing instruction books from the 1940s, they show you all of the 3D rendering techniques later adopted by our modern CGI pipelines. To draw a head, you follow a pattern: draw a cube, carve it up into parts of the head and neck, carve that up into eyes, nose, ears, etc, establish a 3-point lighting system, and render materials. It is very time-intensive and analytical, and required if you didn't shoot a reference photo back then. This is needed for folks who can't visualize, like myself.

Yes, of course. I was a visual artist for a decade before falling down the software hole.