prism
// extrude a closed 2-D shape along an axis
prism {
linear_sweep // or conic_sweep for tapering to a point
linear_spline // linear_spline | quadratic_spline | cubic_spline | bezier_spline
-0.5, // height 1
0.5, // height 2
10, // number of points
// (--- the <u,v> points ---)
< 0.2, -1.0>, < 0.2, 0.2>, < 1.0, -0.2>, < 1.0, 0.2>, < 0.2, 1.0>,
<-0.2, 1.0>, <-1.0, 0.2>, <-1.0, -0.2>, <-0.2, 0.2>, <-0.2, -1.0>
// , <0.2, 0.2> // match 2nd point, if quadratic_spline add this
// , <0.2, -1.0> // match 1st point, if cubic_spline add this as well as the other
// [open]
// [sturm]
}