Girih

Lay Islamic girih tiles in a browser, grow the pattern ring by ring, and save the result as a picture, a vector file or a repeating tile. The settings alone make over 30 billion combinations.

Open Girih

Why this exists

I was pulled in by the craft and the mathematics behind these patterns, and more so after seeing the Alhambra myself and visiting Marrakesh and Fes. I wanted a way to explore the subject by hand, interactively, and to have fun doing it, while respecting the tradition it comes from. So I built one.

One family, several traditions

What I had been looking at in those three places was not one thing. Islamic geometric ornament is a family of related crafts, worked in different materials, in different regions, at different times.

The Alhambra calls its tilework alicatado, and describes it the way a craftsman would: a polygonal unit, repeated, able to go on without end. The Moroccan craft is zellij: a glazed tile is fired, the shape drawn on it and carved out with a mallet, and the cut pieces fitted into a mosaic, each one shaped to match exactly the gap the design leaves for it. Granada and Fes are one tradition.

Girih is the branch further east, the Persian one. It is a way of designing rather than a way of cutting tile, and the same design gets transferred into glazed brick, into cut-tile mosaic, into carved plaster, wood and stone. That is the branch this app draws.

What "girih" means

Girih is Persian for "knot": a knot in a thread, a knot in wood, a button, and by extension a difficulty. Making these patterns is girih-sāzī, the art of making knots.

The app is built from five tiles: a decagon, an elongated hexagon, a bowtie, a pentagon and a rhombus. Every edge of every one of them is the same length, and two lines cross the midpoint of each edge at a fixed angle, so when two tiles meet edge to edge the lines run straight on across the join. Every angle in the set is a multiple of 36°, so whatever you build comes out with decagonal geometry.

The construction is called polygons in contact. Lay down a network of polygons, put two lines through the midpoint of every edge at one chosen angle, and extend them until they meet. The angle is the artist's choice, and it changes a pattern more than any other setting here.

Where the colours come from

The app's colour schemes are named for real crafts. Twelve are the girih tradition's own places, from Isfahan and Fes to Konya and Granada. Sixteen more borrow from crafts outside it altogether: Delft tin glaze, Talavera from Puebla, Imari porcelain, Byzantine mosaic glass, Pompeian fresco, the pigments of the Book of Kells.

Each one is built from the colourants that craft really used, down to which oxide gives which colour and what the dark line is made of. I wrote down where they come from: the place, the century, and what is unusual about the way each one uses colour.

Further reading