Croissant is a surface parametrized as follows:
x=(R+1.6 r sin(v/2) cos(u)) cos(v),
y=r sin(v/2) sin(u),
z=(R+r sin(v/2) cos(u)) sin(v).
**Authors: [Erich Fuchs](https://www.forwiss.uni-passau.de/~fuchs/), [Manfred Kuhnkies](https://www.forwiss.uni-passau.de/de/staff/95/) and [Alexander Zimmermann](http://www.forwiss.uni-passau.de/~zimmerma) from [FORWISS Institute](https://www.forwiss.uni-passau.de/de/projects/64/)**
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