Function sweep_ellipsoid_along_line 

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

Everything the ellipsoid about center passes through as it slides without turning by slide. Its semi-axes are semi_axes[0] along x_direction, semi_axes[1] square to it toward y_hint, and semi_axes[2] along their cross product (as crate::make_ellipsoid_brep).