_squircularCyl script, (non-uniform), by Brian McMillin 2/13/2022.

This script produces a square to round cylinder, as per page 27 of the paper by Fong for the Fernandez-Guasti squircle, which is an intermediate shape between the circle and the square:
https://arxiv.org/ftp/arxiv/papers/1604/1604.02174.pdf
(For a uniform squircular cylinder, just extrude one squircle.)

loft suggested.

extruding the top and bottom squircles, and blending their two edges produces a similar, but different shape.

- Brian