“…The function ρ(n(x), l s , v) gives the BRDF value, ζ a (n(x), l s ) = max(n(x) T l s , 0) accounts for the attached shadow, and ζ c (x) ∈ {0, 1} assign 0 or 1 value to x depending on whether it lies in the cast shadow region or not. e s ∈ R + is a scalar for light intensity value, and n(x) ∈ R 3×1 is the surface normal vector at point x. Eq:(1) is most-widely used photometric stereo formulation which generally works well in practise [9,30,28,65,13,11]. 1.…”