Basic Drawing Made Amazingly Easy (Made Amazingly Easy Series)

is the principle of overlapping. Why does overlapping create depth?
Because our eye understands that there must be some degree of
distance between layered objects.
In this example, the strands of hair that hang in front of and behind
the model’s face create two layers. The head is the middle layer. In
effect, this constitutes a foreground, a middle ground, and a
background. In addition, the bridge of the nose overlaps the far eye,
which also creates a feeling of depth.