Notes on Truchet tilings

A Truchet tiling is a tiling made of the same square tile repeated over and over in a square grid with different orientations. See Wikipedia article. There are very many Truchet pages on the web.
Here is an example made from the tile below left. The sequence of tiles shows a sequence of explorations leading up to the fractal construction explained later.
Tile number and description: 0, as in Truchet's original investigation
change number of tiles in tiling=

Click or on the tiling to change the orientations of the tiles in the tiling.

Space Filling curves

The Smith Truchet tiling of quarter circles is sort of space filling - it fills a lot of space. But for a mathematical space filling curve, we need a limiting process to pass from one level of iteration to another, as for example in the case of the Hilbert curve:

Example: Hilbert curve

Hinged tiling

The iterative process I use to get a mathematically space filling curve from a Truchet tiling is to use a hinged tiling.

Example Hinged tiling

Hinged tiling applied to Truchet tiling

Corresponding L-system

L-systems, (Wikipedia page) describe fractal like structres with words (strings of symbols) describing some fractal process and rules to transform them.
For the hinged tiling, we can label the directions of the paths L or R for whether they turn left or right, and label h and v for crossing horizontal or vertical tile boundaries.

Truchet tiling as image filter

The number of iterations of the process depend on the darkness of an image. It's best to use simple images with strong contrast, e.g., just black and white.

Use the mouse to move the control dots round the screen, or else use the following buttons for different effects.

Reset state of center of tile (this may not produce a noticable effect if there are many iterations)
mouse:

Variable itteration on other deterministic fractals: Sierpinski's triangle