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I really enjoy the style of technical diagrams in many mathematics books published in the mid-to-late 20th century. For example, and as a starting point, here is a picture that I just saw today:

Does anybody know how this graphic was created? Were equations used for the surfaces and then a plotting program used? How was the line-hatching achieved? Here is a another gorgeous picture from David Hilbert's "Geometry and the Imagination":

Again, how was this created? Was it done by hand, then scanned in?

More pressingly: how do I create these kinds of images? Certainly, most of us are familiar with Matlab, Geogebra, gnuplot, or other software for creating mathematical figures, as we are also familiar with vector-based programs like Inkscape and Adobe Illustrator. I've looked at 'old-school' programs like IPE (a little bit like XFig), but still, I don't find them as attractive as the examples above. There is then LaTeX solutions like TikZ. I guess they must surely be hand-drawn, but I would like to know about the process for how these were drawn (and the equipment used).

By way of note, there is an article here about trying to use 3d modeling programs and shaders to duplicate hand-drawn figures.