Ok, so I'm doing things to get my brain into thinking what the best way to create shapes with NURBS is - so I decided to make my own sphere.

I decided to make it by sweeping a circle along a line, and using an arc as the scaling rail - as the following picture shows...



It kind of worked... it made a sphere, but as you can see below, it gave the sphere a circular cap at each end - and I'm not sure why it would do this...?



I played around with the sweep options, but none had any effect on the circular caps.