Function build_pcurve_on_surface_range 

pub fn build_pcurve_on_surface_range(
    surface: &NurbsSurface,
    curve: &NurbsCurve,
    edge_start: f64,
    edge_end: f64,
    forward: bool,
    tolerance: f64,
) -> Result<NurbsCurve, String>

Build a pcurve for a represented subrange of a larger edge curve. Unlike trimming the curve’s homogeneous control net, this samples only the represented interval, which is essential when off-interval control points do not lie on the target carrier.