I am curious what sort of applications people use to make very nice diagrams that often appear in papers and books. I attached an example of the sort of diagram that I am interested in making, particularly the curved coordinate systems (I am typing up some notes on Differential Geometry). Metapost seems useful, but the only real way I can see to create the curved coordinate system is to manually draw in each line via coordinates... which seems unpleasant to say the least.
Thanks for your help!