pub fn offset_intrinsic3(
curve: &Intrinsic3,
distance: f64,
) -> Result<Intrinsic3, GeomError>Expand description
Offset a space curve by distance along its principal normal.
Exact for a helix, where the offset is a coaxial helix. Refused for any
varying law, because the offset is not unit speed and an Intrinsic3
stores arc length: re-fitting would silently change the curve.