Function embed_point 

pub fn embed_point(
    cp: &Vector3,
    origin: &Vector3,
    e1: &Vector3,
    e2: &Vector3,
) -> Vector4

Homogeneous (w (origin + x e1 + y e2), w) for the homogeneous 2-D point cp = (w x, w y, w): linear in cp, so no division — the control point NurbCurve::embed makes of cp.