Function curved_panel 

pub fn curved_panel() -> Program

A doubly curved panel, a saddle: a UV surface (panel) through three ribs along x and three spines along z, each a spline of a 3-D sketch through points of the saddle — the ribs’ and the spines’ meeting where they cross; and a block under it (block, up along y) split along it (shaped) into a piece with the saddle for its top and one with it for its bottom. Drawn in tens of millimetres: the panel is 40 by 30.