pub fn make_ellipse_arc(
center: Vec3,
major_direction: Vec3,
minor_hint: Vec3,
semi_major: f64,
semi_minor: f64,
start_angle: f64,
end_angle: f64,
) -> Result<NurbsCurve, String>Expand description
The arc of the ellipse about center with semi-axis semi_major along
major_direction and semi_minor square to it (toward minor_hint), from
the parameter start_angle to end_angle (radians) of
P(t) = center + semi_major·cos t·x + semi_minor·sin t·y.
Exact: an ellipse is a circle’s affine image, and an affine map carries a
rational curve’s poles and keeps its weights, so this is the unit circle’s
arc (make_arc) with each pole stretched onto the two semi-axes. Either
semi-axis may be the longer.