Show Yuksel's circular/elliptic/hybrid C2 interpolating splines

[mgeier]

http://www.cemyuksel.com/research/interpolating_splines/

Cem Yuksel
A Class of C2 Interpolating Splines
ACM Transactions on Graphics, 39, 5, 2020
https://doi.org/10.1145/3400301

[mgeier]

First, we should probably do Overhauser splines (#12), because they are mentioned as being in the same class.