Consider a second pyramid.
There are twelve shadings of this pyramid.
Consider combining the two pyramids in a single square.
If there are twelve ways to shade each of these pyramids, there are 144 different ways to shade them both.
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.
I found a Celtic knot in a coloring book.
I copied and enlarged it to fit a sheet of paper. There are two cords in this knot. I made five copies and cut out the outlines of the cords.
I glued the lighter outlines to the darker outlines. For one outline, I put a spot of glue at the spot where the outline is under the other one. For the other outline, I cut open the spaces where the outline is under the other one.
I used the fifth copy as a placement guide. I positioned one outline on the guide, then put the other on top of it, gluing the two outlines together.
Slide the cut ends under the other outline, and the knot is complete.
Determine the outline of the cords in the knot. The cords may cross over themselves, forming loops in the outline. Color or decorate the separate cords as you wish. Leave one copy blank.
Cut out the cord outlines.
The two cord outlines in this knot are identical. The cords cross over themselves to form three loops (one is very small). Along each loop, two parallel lines indicate where the other cord crosses over it. For each loop, cut open one (and only one) of these spaces.
Use the third printed knot as a placement guide. Look at the end of the knot closest to you to determine which outline goes on top of the other. Look for the first crossing of the two outlines. Place the cut outlines in position on the guide.
Working from the bottom up, either slide cut ends under or bring cord outline to the front, until you reach the top.