Ruled Hyperboloid

A ruled surface is defined by two functions defining the path of the ends of the lines and lines between them. Here the functions are ellipses so the shape is a hyperboloid.

Rings can added to the top and/and base, useful because the ends of the cylinders are a bit messy.

More on Ruled Surfaces on the blog http://kitwallace.tumblr.com/post/85509667344/surfaces-rule-ok