Imagine a triangle drawn within a square.

Now, group four squares into a block.

Not very exciting, is it?

Now add three converging lines to the interior of the triangle. The flat triangle becomes a three-sided pyramid.

Now, let’s play with the light.

This pattern of pyramids implies a light source that shines on all faces at once.

If we imagine lowering the light source, then only one face at a time is lit, casting the other two faces in shadow. When the light source hits a face full on, the other two faces are in complete shadow. When the light source hits a face toward one end or the other, the neighboring face is in partial shadow, and the third face is in complete shadow. When the light source hits two faces at once, the third face is in complete shadow.

There are twelve different shadings for this one pyramid.