p131fig04.08 Simulation of brightness constancy under an illimination gradient.  Note that the feature content pattern (F) is the same in both cases, so too is the boundary contour (B) pattern that is derived from it, and the final filled-in surface.<BR>|| Simulation of brightness constancy. Discount the illuminant. [stimulus (S), feature (F), boundary (B), output]. B -> F -> S -> B: not veridical, but useful! Ratio-sensitive feature contours (F).