1. A method for sensing a shape of a surface of a reflective object, comprising the steps of: recording an initial image value for a surface point on the object, when the surface is reflecting a visible item in an initial position; recording subsequent image values as the visible item undergoes a predetermined motion, through subsequent positions that are distinct from the initial position; identifying the position of the visible item at which the image value for the surface point becomes substantially identical to the initial image value; and determining a surface normal of the surface point using the initial and the identified position of the visible item, wherein the steps of the method are performed in a processor.