principal curves on surface

hi Daniel, first at all, i thinkg your work is great:)

i have one Question:

in your earlier examples you made some component which make principal curves on surface like this onei´m trying to understand this functions to translate it to my architectural projects, but i must say even if i thin don´t be too dumb in mathematic questions, i still have no too much idea how to implement all that to some script. i had try to use ours spm components, but i have no idea how to use them right. could you help me whit some tip or something ?

thanks a lot Mike