Function discretize_on_surface 

pub fn discretize_on_surface(
    curve: &PlanarCurve,
    range: (f64, f64),
    surface: &SurfaceGeometry,
    deflection: Deflection,
    tol: Tolerances,
) -> OgeomResult<(Vec<Point2>, Vec<f64>)>

Discretize a pcurve with its chord tolerance measured in space, through the surface that gives its chart a metric.

discretize_planar measures in parameter units because it has no surface to convert through; this is the version that does. Each candidate segment is lifted to the surface and the sagitta measured between world points, so one chord tolerance means one thing whatever the chart’s scale: a quarter-turn on a large cylinder refines further than the same quarter-turn on a small one.

Errors

As discretize_planar.