<_description>
Turns a sphere inside out: a smooth deformation (homotopy). During the
eversion, the deformed sphere is allowed to intersect itself transversally,
however, no creases or pinch points occur.
Inspired by the following paper: Adam Bednorz, Witold Bednorz:
"Analytic sphere eversion using ruled surfaces", Differential Geometry
and its Applications 64:59-79, 2019.
https://en.wikipedia.org/wiki/Sphere_eversion
https://mathworld.wolfram.com/SphereEversion.html
Written by Carsten Steger; 2020.