These textures are all produced using inverse two-dimensional fast-fourier transforms.
The fast-fourier transform is the name given to a computational technique first described and implemented in 1965.
One of the most important features of the method from the perspective of algorithmic texture generation is that textures produced using this method always tessellate seamlessly.
This makes them ideal for a wide range of applications where transmitting large areas of texture wastes bandwidth, and where a small texture may be tessellated to cover the area.
Such applications include computer games, virtual reality and pages designed for the world wide web.
The textures here are designed to simulate natural surfaces.