The shading of the cylinder lying on its side , represented above by a
roll of paper, is complicated by the effects of the cast shadow on the
cylinder's shaded surface as it curves into contact with it. Like
the upright cylinder. the sequence of values follow "light side, terminator,
core, reflected light" but then quickly becomes darker as the cylinder's
approaches contact with the table where the cast shadow cuts off all light.
This point of contact between the cylinder and the surface on which it
rests is extremely dark.
In the schematic drawing (below) of the cylinder's end, this darkest
area is between the reflected lights areas on opposite sides of the shaded
half of the cylinder.
