snek is a simple data structure for working with vertices and edges. More importantly it is a programming pattern for applying changes to the structure. It is specifically written to be useful for a broad range of ways in which i usually write generative algorithms for creating art.

The pattern depends on the concept of alterations. In short: an alteration is a change that will be applied to the structure at the end of a given context. alterations are further described in http://inconvergent.net/snek-is-not-an-acronym/.

Here is and example of manipulating a snek instance called snk using alterations:

; context start
(with-snek (snk)
  ; iterate
  (with-all-verts (snk v)
    ; move alteration
    (move-vert v (rnd-in-circ))
    ; w will be an arbitrary
    ; vertex in snk
    (with-rnd-vert (snk w)
      ; join v and w if they are closer than d
      (if (< (vert-dst snk (v w)) d)
        ; join vertices alteration
        (join-verts v w))))
; context end
; alterations have been applied

There are two more examples. They can be executed like this:

./run-slope.lisp res/slop.png
./run-lines.lisp res/lines.png

Notice that the resulting image will end up in res.

snek is used in

Dependencies

This code requires Quicklisp and zpng. Note that the The path to quicklisp must be set in src/load. zpng is automatically installed via quicklisp.

Run tests

There are some tests included. Run them like this:

./run-test.lisp

Stability changes and Versioning

This code is highly experimental on my part. It is likely to change with no warning or explanation. I will keep a note of the version number in VERSION.

On Use and Contributions

This code is a tool that I have written for my own use. I release it publicly in case people find it useful. It is not however intended as a collaboration/Open Source project. As such I am unlikely to accept PRs, reply to issues, or take requests.

Todo

Randomized order of alteration apply
Maintain list of singly-connected vertices?
zonemaps? kd-tree?

Done

Reject/attract force move alterations, or force calc funcs? (sort of)