Steven Pinker -- How the Mind Works - Hampshire High Italian ...

254 | HOW THE MIND WORKSlike their counterparts in the image, requiring as little gray paint as possihleto finish the job.Finally, the reflectance specialist—the painter—gets the model. Itis the specialist of last resort, and its task is to take care of anyremaining discrepancy between the image and the model. It finishesthe job by proposing different shades of pigmentation for the varioussurfaces.Does the program work? Adelson and Pentland presented it with afanfold object and let it rip. The program displays its current guess aboutthe object's shape (first column), its current guess about the direction ofthe light source (second column), its current guess about where theshadows fall (third column), and its current guess about how the objectis painted (fourth column). The program's very first guesses are shown inthe top row.OriginalImage3-D Shape Light Source Shading SurfaceiOhlii]ur View) Direction Pattern ColoriioiStartFinish•Finish(1)The program initially assumed that the object was flat, like a 2-13painting lying on a table, as in the top of the first column, (It is hard todepict this for you, because your brain insists on seeing a zigzag shapeas being folded in depth. The sketch is trying to show some lines sittingflat on the page.) The program assumed the light source was beadon,from the direction of the eye (top of the second column). Withthis flat lighting, there are no shadows (top of the third column).The reflectance specialist bears all the responsibility for duplicating the