Technique · Fields
Moire patterns
Two or three fine gratings of lines, rings, dots or spokes laid over one another and slowly turned, making broad fringes that belong to neither.
Moire patterns is a field drawn for every pixel by the graphics chip. Every piece on Synapse Drip is made from a recipe that layers techniques like this one, and you can change any of it in the Studio.
Good to know
- Banknotes and ID cards often include fine overlapping line patterns whose moire changes when the document is copied or tilted, which makes them hard to reproduce.
- Printers choose the angles of their cyan, magenta, yellow and black screens, traditionally about 15, 75, 0 and 45 degrees, so that the moire between them is a small rosette rather than a visible pattern.
- In 1963 the biophysicist Gerald Oster and a colleague described moire patterns in Scientific American, and the article helped to make them a favourite of op artists.
- Moire is the French word for watered silk, whose pressed weave shows the same wavy bands; the pattern is also a nuisance in printing and television, where fine fabrics seem to shimmer.
- Engineers measure strain with moire: a fine grating is printed on a part, a second one laid over it, and the fringes move when the part stretches.
The mathematics
- Two gratings of frequencies f and 1.030 f, turned by 4.58 degrees, beat at the difference of their frequency vectors, so the fringes are about 0.206 of the picture's height apart, much wider than the lines themselves.
- A tiny turn of one grating swings the fringes through a large angle, which is why moire can measure the strain in a part to a small fraction of a line spacing.
- The fringes are the difference of two frequencies, the same effect as two musical notes a little apart making a slow wobble of loudness, which is called a beat.
In art
- Op art painters such as Bridget Riley and Victor Vasarely, and the 1965 exhibition The Responsive Eye at the Museum of Modern Art, made moire-like shimmer a subject in itself.
- The pattern has no author in the picture: no one draws the broad fringes, they appear where the two gratings happen to line up, which makes them a favourite of generative artists.
More ways to use it
Related techniques
Nebula and stars · Liquid · Droplets · Network · Terrain and maps · Neuron · Order to chaos · Fractal tree