Function surface_derivatives 

pub fn surface_derivatives<P: Blend>(
    ku: &KnotVector,
    kv: &KnotVector,
    grid: &ControlGrid<P>,
    u: f64,
    v: f64,
    order: usize,
    tol: Tolerances,
) -> OgeomResult<DerivativeGrid<P>>

Evaluate a surface and its partial derivatives up to total order order.

result[k][l] is the derivative taken k times in u and l times in v, so result[0][0] is the point itself.

Errors

As evaluate_surface.