Why two gratings are enough
Almost every piece in this gallery starts with the same idea: draw one regular structure, draw a second one almost like it, and let the eye find the third.
A moiré pattern appears when two regular structures overlap with a small difference in spacing, angle or position. The result is a slow, wide fringe that neither layer contains on its own. It is the cheapest kind of complexity there is: two lines of code and a rotation.
I keep the rules narrow on purpose. One layer is always perfectly regular. The second layer changes by a single parameter, and I do not touch anything else until I understand what that one change does. Most of the work is simply looking at the result for longer than feels necessary.
The pieces in the gallery are vector files, so they stay sharp at any size. If you want to see how a single parameter changes the look, the downloads page has a small pack with the first eight pieces in their original form.