Hi,
The forum engine got rid of [i] even in the code, so we turned off the italic BBCode feature. Please try the code again, now it should work.
If you still see the twist at the apex, please write back the library version you are using. (gravity_tube has been corrected in a library update, it’s possible that your version doesn’t contain that update yet.)
Péter Baksa
Library Platform, Software Engineer
GRAPHISOFT SE