Here's another interesting result. This is a one-rail sweep, with a nearby straight line set as the scaling rail.

Each cross-section of this shape is a different sized circle, but they are scaled in such a way to produce a straight line along that one side.

When you use a one-rail sweep with a scaling curve, the "Maintain height" checkbox will appear, which lets you control whether the scaling is a stretch in one direction (in the middle here) or a uniform scaling.



- Michael