Wow, my laborious-seeming TikZ workflow actually looks pretty simple in comparison! It's all in the one tool and the entire picture code is right there in the Latex source, easy to edit and version control. Shading on a surface is not something I've got nice yet, and lines becoming occluded is a manual effort, but I'm pretty sure I could produce something like the 6 hour figure on p24 in quite a bit less time than that.
Edges of surfaces caused by things like hills obscuring other parts of the same surface, or the surface curving back behind itself (many examples of both on p2 of this) are something I don't have a good way to do. I have done it by doing edge detection on an OpenGL depth buffer and vectorising the results, but that's hard to integrate with TikZ, and changing view angle means doing it all again. Shadows are another problem.
