I think parent's suggestion could work great if you printed the Asymptote results and then traced them in ink and scanned those. As for computer generating tha

I think parent's suggestion could work great if you printed the Asymptote results and then traced them in ink and scanned those. As for computer generating that style, I might look for brushes for Photoshop/GIMP/Illustrator/Inkscape that produce the style you are looking for, and then reverse engineer those or use scripting capabilities of whichever tool to produce the figures.