Function sphere_eclipse_vector 

pub fn sphere_eclipse_vector(
    earth: &Vec3,
    r: &Vec3,
    c: &Vec3,
    rsphere: f64,
    lam1: &mut f64,
    lam2: &mut f64,
) -> bool

This version of sphere_eclipse tells you whether or not a given sphere will eclipse a given point at a particular phase or not. If the answer is yes, it will also return with the multiplier values giving the cut points. These can then be used as starting points for Roche lobe computations. These can then be used as the starting point for later computation. Points inside the sphere are regarded as being eclipsed with the lower mulitplier set = 0

\param earth vector towards Earth \param r the position vector of the point in question (units of binary separation) \param c the centre of the sphere (units of binary separation) \param rsphere the radius defining the sphere enclosing the star (units of binary separation) \param lam1 if eclipse by the sphere, this is the start of the multiplier range \param lam2 if eclipse by the sphere, this is the end of the multiplier range \return false = not eclipsed; true = eclipsed.