"(the 2d-projection of) a helix" is exactly what I meant, because I want to make drawing such as: http://en.wikipedia.org/wiki/File:SpringsInParallel.svg
"(the 2d-projection of) a helix" is exactly what I meant, because I want to make drawing such as: en.wikipedia. org/wiki/ File:SpringsInP arallel. svg
http://