Function ray_vs_sphere 

pub fn ray_vs_sphere<T: Float + FloatOps<T> + NumberOps<T>, V: VecN<T> + VecFloatOps<T>>(
    r0: V,
    rv: V,
    s0: V,
    r: T,
) -> Option<V>

returns the intersection point of ray with origin r0 and direction rv against the sphere (or circle) centred at s0 with radius r