Grasshopper does not seem to have the “pick region” feature from the Rhino Hatch command. I have created such an algorithm, taking advantage of recursive computing provided by the Hoopsnake plugin. You can download the .gh file here: FindRegion.gh
The overall idea of the algorithm is to find the curve that has the shortest angle relative to the previous one. For this to happen, a lot of mid actions need to take place, which are somewhat explained in the definition itself.
If you find bugs, care to contact me!
[edit] In order to avoid using the third-party plugin Hoopsnake, I have devised an alternative approach using SrfSplit. It is much slower, but yelds correct results.
SrfSplit approach:
Hoopsnake approach:
