This is my project — thanks for the interest. I just made it more mobile / small device friendly.
The app is primarily based on ideas of Hertzmann and Zorin in [this paper](https://cims.nyu.edu/gcl/papers/hertzmann2000iss.pdf), using directions of principal curvature for hatching directions.
Very cool, I made a very primitize plotter before that let you draw on the UV plane and project curves onto the surface (helpful for fundamental groups) / included a time parameter for homotopies. If you're looking for feature ideas I think those would be great! https://tobylam.xyz/3d-plotter
Pretty, and a lot of fun to tweak around the parameters.