Function fill_boundary 

pub fn fill_boundary(
    bottom: &Curve,
    top: &Curve,
    left: &Curve,
    right: &Curve,
    samples: usize,
    tolerance: f64,
    tol: Tolerances,
) -> OgeomResult<Fitted<BSplineSurface>>

Fill the region bounded by four curves with a fitted patch: the transfinite Coons blend of the boundaries, sampled and fitted, its error reported.

The curves must close corner to corner in the order given (bottom runs with u, top above it, left and right with v), each traversed over its own domain. The patch interpolates the Coons surface’s samples to the stated tolerance; the Coons surface itself interpolates the boundaries exactly, so the fit error is the whole distance between the returned patch and the boundary it fills.

Errors

OgeomError::Construction if the corners do not meet within tol, plus whatever the fit refuses.