Function make_ellipsoid_brep 

pub fn make_ellipsoid_brep(
    center: Vec3,
    x_direction: Vec3,
    y_hint: Vec3,
    semi_axes: [f64; 3],
) -> Result<BrepSolid, KernelRefusal>

The solid ellipsoid about center with semi-axes semi_axes[0] along x_direction, semi_axes[1] square to it toward y_hint, and semi_axes[2] along their cross product.

Exact: the unit ball under the affine map that stretches it onto the three semi-axes, which carries the ball’s rational poles and keeps their weights. Its one face is closed on a seam, the half ellipse from pole to pole through the first semi-axis, and its poles are the ends of the third.