## Sunday, May 30, 2010

### Self-Similar Vertices

I've been using the process described here to create tilings from a pentagon and triangle. These tilings, or tile patches, are one solution to a problem I encountered while generating tilings as structures for a series of vertex pattern diagrams. I needed a way to create greater density changes than I was getting with other tilings. Self-similar tile sets solve the problem.
My interest in tilings is more art than math. The tile set I’m using is closely related to, and can be derived from tilings described by Robert W. Fathauer (see Reference below). Fathauer found two families of self-similar tilings based on segments of regular polygons. One family includes an 18-18-144 triangle that is a segment of a regular decagon. The triangle is the s=10 prototile described by Fathauer. The tile set that I use includes a pentagon as well as the triangle. The pentagon is the shape that remains after removing five s=10 tiles from a regular decagon. Other hexagonal or square prototiles can be combined with triangles to make self-similar tile sets.

So, this method is based on an infinitely self-similar tile set consisting of pentagons and 18-18-144 triangle prototiles. Tilings should be edge-to-edge, with no overlaps. Gaps are inevitable, but they should allow lining with infinitely scaled tiles. Tilings will not fill the plane but should be infinitely scalable at the boundaries, as in a fractal. These are actually tile patches, not tessellations.

The initial pentagon and triangle prototiles are sized so the long side of the 18-18-144 triangle is equal to the pentagon side. Each subsequent pentagon-triangle pair is scaled so that the next pentagon side is equal to the short side of the previous triangle. Using this scheme, as the boundaries of the tiling grow outwards they form singularities, or gaps surrounded by tiles. The inside edges of these gaps can be continuously and infinitely lined with scaling pentagons and 18-18-144 triangles, or just 18-18-144 triangles.

An interesting feature of these prototiles is that the ratio of the areas of each pentagon to the next smaller pentagon (or triangle to triangle) is always 3.618... or 2 plus Phi.

It's possible to create numerous symmetrical tilings with these tiles, but I often choose to create asymmetrical diagrams. The processes, lattices, and patterns I use are not math. I'm influenced by structures in math, science, architecture, and design, but unconstrained by the rigorousness of math. These diagrams have no practical use or purpose other than art.

Reference:

Fathauer, Robert W. (2000). "Self-similar Tilings Based on Prototiles Constructed from Segments of Regular Polygons," presented at the Bridges Conference (July 28-30, 2000, Southwestern College, Winfield, Kansas).
http://www.mathartfun.com/shopsite_sc/store/html/Compendium/Bridges2000.pdf
Also see:
http://www.mathartfun.com/shopsite_sc/store/html/Compendium/encyclopedia.html