akhileshs / snek

v2.x.y-beta An experimental system for writing generative systems.

SNEK is Not an Acronym

About

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.

About the Name

A while back someone on twitter suggested that if Python 3 was named "snek" it would avoid naming confusion. I found that amusing at the time, and picked snek as the placeholder name for this project. I've been looking for a better name, but I haven't found one yet.

Alterations

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/.

I have also written about things related to snek at

• http://inconvergent.net/a-propensity-for-mistakes/ (indirectly about snek)
• http://inconvergent.net/a-method-for-mistakes/
• http://inconvergent.net/arbitrary-alterations/
• http://inconvergent.net/grains-of-sand/ (about "sandpainting", see src/sandpaint.lisp)

Here is and example of manipulating a snek instance called snk using alterations. Alteration constructors are postfixed with ?.

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

Custom alterations

You can define your own arbitrary alterations. There is an example of this in ex/custom-alt.lisp. I have also written about it here: http://inconvergent.net/arbitrary-alterations/

Examples

There are some examples included. All examples are in the ex folder.

if you don't provide a result name as the first argument, then the resulting file will be named tmp.png.

This includes a few samples of how to use the plotting functionality. This will export a simple vector file and an image to indicate the result.

Usage

snek is used in

• http://moment.inconvergent.net/
• https://twitter.com/sandpaintbot
• https://twitter.com/scratchpaintbot
• https://twitter.com/cronianrings

Dependencies

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

• http://www.xach.com/lisp/zpng/
• https://www.quicklisp.org/beta/

Tests

There are some tests included, see the test folder.

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 src/load.lisp.

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.

Planned Changes

• Randomized order of alteration apply
• one-ring/ incident edges

THANKS

I would like to thank

• https://twitter.com/RainerJoswig
• https://twitter.com/paulg
• https://twitter.com/jackrusher

Who have provided me with useful hints and code feedback.