         return Vector()
     }
     
-    /**
-        Return the time t that the ray first intersects the 
-        object, or nil if no hit occurs
-    **/
     func intersection (ray:Ray) -> Double?
     {
         return nil

{
    var centre:Vector = Vector(x: 0.0, y: 0.0, z: 0.0)
    var radius:Double = 1.0
    
    /** 
        Currently using a geometric solver. 

    func intersectionPoint(ray:Ray) -> Vector?
    {
        if let t = intersection(ray) {
            return ray.t(t)
        }
        return nil
    }
