Additional images: Anaglyph, Anaglyph Wireframe, Parallel Stereo
Unduloid describes a family of surface of revolution. Let a conics section roll on a line. Its focus traces out a curve. This curve revolved around the line generates the unduloid. The above image shows an unduloid where the rolling curve is an ellipse. It has a mean curvature of 1. If the rolling curve is a parabola, a catenoid will be generated, and has mean curvature of 0.
This movie shows the generation of unduloid by rolling an ellipse.