24.4 Edges in an image can correspond to a variety of scene events. Consider the photograph on the cover of your book and assume that it is a picture of a real 3-D scene. Identify a set of ten different brightness edges in the image, and for each, decide whether it corresponds to a discontinuity in

(a) depth,

(b) surface normal,

(c) reflectance, or

(d) illumination.