Function to_nurbs 

pub fn to_nurbs(
    model: &mut Model,
    shape: &Shape,
    tol: Tolerances,
) -> OgeomResult<Built>

Rebuild a solid, a shell, a face, or a compound of them, with every surface and curve in B-spline form.

The result is a new shape of the same kind in world coordinates (every occurrence placement baked in), whose geometry is exactly the original’s wherever the conversions are exact (everywhere but the fitted pcurves, whose error is bounded by the fit target derived from the tolerance). History records each original face, edge occurrence and container modified into its converted twin.

Errors

OgeomError::Construction if the shape is not a solid, a shell, a face or a compound of them, or a conversion has no exact form (a trimmed surface’s basis is converted; nothing else refuses); OgeomError::NotDone if a pcurve refit cannot reach its target.