Andy Lomas' "Aggregations"

Andy Lomas: DLA fractal art

Andy Lomas makes computer simulations of things that look a little like limescale deposits in water-pipes ... but really pretty limescale deposits. They're another example of the DLA (Diffusion Limited Aggregation) fractals mentioned earlier (like my iced-up fridge!), but his are computer-simulated at extremely high resolution, and can contain between around fifty to a hundred million individual particles.

• Andy Lomas' profile on CGSociety

More unusually, he's also done high-resolution plots of the tracks that particles took to reach those points, which gives a sort of inverse "ferny"-looking or lichen-like pattern. You can see some of his "Images of Aggregation" and "Images of Flow" art on his website.

Moorish-styled Tiles

'Granada' range tiles, FiredEarth.com

I think these tiles are absolutely gorgeous. They’re based on classic Moorish tiling artwork from Spain. If you know the Alhambra in Granada (widely regarded a representing the pinnacle of Islamic geometrical art), you’ll know roughly what to expect (M.C Escher made a pilgrimage to the Alhambra to study its designs before embarking on his series of famous tesselated artworks, and some of the Alhambra's designs also seem to show up in the work of Roger Penrose).

The borders between the smaller protruding glazed shapes are recessed and unglazed, so that each tile looks as if it's been assembled from a mosaic of smaller and more complicated tile shapes. It's a nice surface.

The Granada range of tiles is made in Spain and sold by Fired Earth. They also do other North African and Middle Eastern designs without the mosaic effect, like the Andalucia and Anatolia ranges.

(Thanks to Mark at FiredEarth Brighton for providing background info and letting me take the photos)

Fibonacci Textiles

Fibonacci quilt (Louise Mabbs)

Today I popped along to an exhibition in Portslade, of quilts and textiles designed around the Fibonacci Series ("Fun With Fibonacci 2"), part of a larger display called Art in Creation 3 (19-21 May 2011).

The main exhibiting designer, Louise Mabbs, also creates fabric origami, and other mathematically inspired hybrid pieces.

A Koch Snowflake Sponge

Koch Snowflake Sponge

After the little triumph of the Koch Snowflake Solid, here's a better one: this beastie doesn't just give you the Koch Snowflake profile, it's also punctured by an infinite number of little Koch-snowflake-shaped copies, as holes.

It's a sponge!

The method's pretty much the same as before: divide your source cube into a 3×3×3 grid and delete the eight corners, but then also delete the central cubelet.
When you carry out the very first division it seems that deleting the centre shouldn't change the shape in any way, because the centre cube is totally isolated from the outside world by its six face-adjacent neighbours, but as the number of iterations increases, the cubelets get their corners progressively nibbled away and you get to peek through the holes created by the missing corners into the central void (and out of the other side).

At each iteration the sponge opens up a new set of hexagonal holes, and the existing holes open out and grow more Koch-Snowflakey detail.

This is a way cooler shape than the last one ("It's a sponge!").

And again, for the ultimate verification, I have a real one sitting on my desk made out of plastic.

The Impossible Snowflake

3D Koch Snowflake

Since the 2D Sierpinski Carpet projects nicely into 3D to give the Menger Sponge, and the 2D Sierpinski Triangle similarly up-dimensions to give the Sierpinski Pyramid, it seems obvious to try to get a 3D version of another famous 2D fractal construction, the Koch Snowflake.

A number of people have probably tried this over the years, but I haven't seen anyone manage it. The snag is that the "obvious" solution doesn't work. We're taught that the Koch Snowflake outline is created by assembling triangles, but if we try to use the most obvious triangle-based solid, the tetrahedron, we fail ... starting with a single tetrahedron and adding half-scale copies to each side initially produces a six-pointed profile, but after that it all goes horribly wrong (book, page 20). People have tried offsetting the positions of the daughter pieces to try to keep the shape looking interesting, but it's kinda cheaty.

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So the secret to creating this "impossible" solid is not to use a standard approach. "Step One" is to understand that the Koch Snowflake doesn't have to be made out of triangles, it can also be built from hexagons (book, Figure 3.13, page 26), and "Step Two" is to remember that the simplest Platonic Solid with a hexagonal profile is the cube  ... when viewed corner-on.

The rest turns out to be simple. Take a cube, apply a 3×3 grid to each face to divide it up into 27 smaller cubes, and throw away the eight corner-pieces. Then do the same thing for each of the smaller remaining  cubes, and repeat.

The resulting fractal solid (diagrammed as Figure 37 in the book) has a crosslike fractal pattern on each of its six faces, and shows a perfect Koch Snowflake silhouette when viewed from each of the original cube's eight corners.

A 3D Koch Snowflake ... paperweight

I have one of these that I'm using as a paperweight. It's perhaps not the prettiest of fractal solids, but I suppose that it's not bad for something that wasn't really supposed to exist.

The Diamond Eye Fractal

Starting the fractal tiling process ...
(click any image to enlarge)

The "Diamond Eye" is a fractal that I snuck into the book at the last minute as a small pagespace-filler without a title or figure number (on page 31). As a result, it's probably too small to see properly.

At first sight, this fractal looks like a fairly intricate (but unsignificant) crystal growth pattern with two competing seed types (in this case, clusters of horizontally- and vertically-aligned diamonds).

Iterations 3-5

We start with a horizontal diamond-shaped space, and add our first piece, a vertical diamond smaller than the original by a ratio of the square root of three (1.732-something). It wedges exactly across the centre of the space (top diagram, middle), and then we can’t go any further, so we switch to the second configuration. Scaling down by another factor of root[3], we can fit two horizontal diamonds into the left and right corners of the original space (top, right). Switching back to vertical mode, we can then wedge in four more smaller copies of the shape, and switching back to horizontal again lets us shove in a further eight. As the number of iterations increases we end up with a single solid mass of vertical diamonds growing out from the centre, competing with a hollow shell of horizontal diamonds growing in from the perimeter.

Iterations 6-8

Here’s what you end up with when you’ve carried out so many stages that you effectively have a single, solid,  frozen block (click to enlarge).

Fractal Rhombic Mesh

The important thing here is the shape of the boundary between the two “crystal” types. You can’t really see it too well in the above diagram, so we’ll colour the horizontal and vertical diamonds differently to emphasise the boundary.

Rhombic Koch Snowflake (interior and exterior)

Aha! And this is when we realise that what this “dual diamond” construction is really doing is sneakily growing a Koch Snowflake (I would have put "Rhombic Koch Snowflake" as this post's title, but it would have given away the punchline).

The internal network of cross-crossing diamond-ey shapes are still a bit distracting, so we’ll delete one of the two components. We’ll delete all the vertical diamonds and leave just the horizontals.

Rhombic Koch Snowflake (exterior only)

Yep, definitely a Koch Snowflake!

A Tilable Space-filling Fractal Sponge

A fractal, tileable sponge ("Alt.Fractals", p.61)

Okay, so this one looks like a "stretch" version of the conventional Menger Sponge, using a 4×4×4 grid instead of 3×3×3 .. and it is ... but it's a bit more than that. It's not just an arbitrary variation on a math standard.

It's a space-filling solid.

Space-filling solids are kinda rare. A cube will tile 3D space (obviously), but the other Platonic Solids won't, at least, not individually. A small group of other regular-ish solids have the property, like the truncated octahedron (which has a mix of square and hexagonal sides), and the rhombic dodecahedron (which has twelve identical diamond-shaped faces), but you won't normally find any mentions of space-filling solids that are also fractals.

Let's look at this shape further. It's constructed by taking a cube and dividing it into a 4×4×4 grid of smaller cubes, and deleting central 2×2 columns through the centre of each face (and then repeating, ad infinitum).
The 4×4×4 grid gives us 64 smaller cubes, so when we then delete four cubes per face, and eight from the centre, we're eliminating 6×4+8=32 cubes, out of the original 64. Every time we cut a new generation of holes, the remaining volume of the sponge halves.

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Now, how it tiles.

For the "zeroth" generation, we just have a simple cube, which will (obviously) tile an infinite 3D space as an array of (infinity^3) individual pieces. Now cut the first generation of holes into each piece. The holes punch an intersecting series of aligned 2×2 tunnels through the array, and where the 1×1 edge-columns of adjacent cubes touch, they form an intersecting series of 2×2 beams. The networks of columns and tunnels have the same shape, and we've already established that they have the same volume, so after one generation, we can take our infinite array, make a copy of it, and fit the copy exactly into the holes of the original to make it totally solid.

If we then take our resulting solid "dual" array, and cut the second-generation holes into each individual piece, the volume again halves, the new holes in both arrays again line up, and again we have identical networks of solids and spaces. Again, we can fit an identical offset copy of the original exactly into the spaces.

This goes on forever. For one of these sponges with n generations of holes, you can tile space solidly with n^2 overlapping copies of the sponge coexisting in the same space, so for the third-generation sponge shown in the photograph, you can interleave eight of them together.

For the "perfect" version of the sponge, with an infinite number of holes, you can tile space solidly with a block assembled from (2^infinity) overlapping "same-size" copies existing in the same space. Strange, but true.


So, it's Challenge Time! Can anyone find any other fractal solids that will completely tile space at a fixed size?