In this sketch of the painter thoams kinkade, the entire hand is treated as a block, with front A and side B. Each phalanx of each finger is also treated as a cube. When the face-to-face transition turns, Rubens deals with a strong contrast between light and dark,

 

which is most clearly seen at the intersection of block c and block D. Notice the projection (E) on the front side, this shadow disappears on the side, because the main light source leaves the projection on the side never seen. The projection of the reflected light may be on the side, but this is rarely allowed.

 

(by thomas kinkade gallery)