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Self-similar structures

 
Produced by Andy Burbanks


The picture is a realisation of a recursive tree-like structure (see the movie below). There is a central drive shaft with three arms attatched. Each of these in turn has 3 of its own sub-arms, and so on through a few levels of recursion. The structure sits atop a platform inscribed with an escher-style tiling

Once the rules defining such a structure have been designed, it is modelled 3-dimensionally using some simple recursive C++ routines. The model is then rayshaded using the package Persistence of Vision (POVRAY).


The image to the right was previously used as a School logo for the WWW pages of the School of Mathematics. The object is called the Sierpinski Gasket and is constructed by following a simple rule repeatedly: begin with a pyramid, and at each stage replace each pyramid by four smaller copies (arranged to fit neatly inside the original), repeat the process.

Note: the picture shown differs from the usual Sierpinski Gasket, in that I have used five pyramids at each stage to give a square-base to the structure.


The Menger sponge

Recipe

  1. Take one cube
  2. Divide into 27 smaller cubes, evenly
  3. Remove all the cubes that are in line with the centre of a face of the original cube (warning, this is the tricky bit! the whole structure is prone to fall apart)
  4. Repeat the process on all resulting cubes

Movies

Several pictures can be combined into a movie, using the mpeg_encode package. With careful use of both C++ and shell-scripts, the whole process can be automated.

Clicking on the picture below gives a movie of the recursive propeller which demonstrates what happens to this particular structure as a parameter is varied. The parameter being changed is the angle of attachment of the arms (and thus the angle of attachment of the sub-arms and sub-sub-arms, and so on).

I have made an effort to make the object look physically realistic (although I wonder what mechanism the gold spheres would have to contain in order for this object to be constructed physically!).

 MOVIE Mpeg movie

I suggest that you load the movie to your local disk and play it there in loop mode if you want to see more revolutions of the propeller.

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