Function construct::contour

pub fn contour<T: Float>(a: Fn2<T>) -> Fn1<T> where
    f64: Cast<T>, 

Gets the contour line of a curved quad.

0.0-0.25: [0.0, 0.0] -> [1.0, 0.0]
0.25-0.5: [1.0, 0.0] -> [1.0, 1.0]
0.5-0.75: [1.0, 1.0] -> [0.0, 1.0]
0.75-1.0: [0.0, 1.0] -> [0.0, 0.0]