RasterWalk

Translated by Daniel Howe

Based on: Random Walk Through Raster by Frieder Nake
Category: direct
Direct translation of Frieder Nake's 1966 "Random Walk Through Raster" from Computer Graphics and Art, May, 1976, Vol. 1, No. 4, Pg 6-7 Copyright (c) 2012 Daniel C. Howe. To see this sketch run in JavaScript, go to: http://rednoise.org/sketches/RasterWalk/
        
/*
 * This sketch is part of the ReCode Project - http://recodeproject.com
 * Computer Graphics and Art - May, 1976 - Vol. 1, No. 4 - Pg 6-7
 *
 * "Random Walk Through Raster"
 * by Frieder Nake, 1966
 *
 * direct recode by Daniel C. Howe
 *
 * Copyright (c) 2012 Daniel C. Howe
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:

 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

let x = 50,
  y = 50,
  cellSz,
  grid = [];
let DOWN = 1,
  RIGHT = 2,
  px = 0,
  py = 0,
  sw = 2;

function setup() {
  createCanvas(400, 400);

  background(255);
  noFill();
  strokeWeight(sw);
  strokeCap(PROJECT);

  makeGrid();
  foreach(drawCell);

  doStep();
}

function drawCell(j, i) {
  // skip one row/col around edge
  if (i > 0 && j < y - 1 && i < y - 1 && i < x - 1 && j < x - 1) {
    let off = 0;
    stroke(0);
    if (!exists(j, i, DOWN)) {
      stroke(255); // erase
      if (j > 1) off = sw;
    }

    if (j > 0) {
      line(
        j * cellSz + off,
        cellSz + i * cellSz, // horiz
        (j + 1) * cellSz - 1,
        cellSz + i * cellSz
      );
    }

    off = 0;
    stroke(0);
    if (!exists(j, i, RIGHT)) {
      stroke(255); // erase
      if (i > 1) off = sw;
    }

    line(
      cellSz + j * cellSz,
      i * cellSz + off, // vert
      cellSz + j * cellSz,
      (i + 1) * cellSz - 1
    );
  }
}

function makeGrid() {
  let d = dist(0, 0, 1, 1);
  cellSz = min(width, height) / x;

  for (let j = 0; j < x + 1; j++) {
    grid[j] = []; // initialize to 0
    for (let i = 0; i < y + 1; i++) grid[j][i] = 0;
  }
}

function doStep() {
  let dirs = Math.random() < 0.9 ? [DOWN] : [RIGHT, DOWN];
  let idx = floor(random(dirs.length));
  let dir = dirs[idx];
  removeSpot(px, py, dir);

  // but weight verticals and the diagonal
  let d = dist(px, 0, py, 0) / x;
  if (Math.random() < d) removeSpot(px, py, RIGHT);

  drawCell(px, py);

  if (++px % x == 0) {
    px = 0;
    ++py;
  }

  if (py < y - 1 || px < x - 1) setTimeout(doStep, 0);
}

function foreach(fun) {
  for (let i = 0; i < y; i++) {
    for (let j = 0; j < x; j++) fun.apply(this, [j, i]);
  }
}

function exists(j, i, side) {
  switch (side) {
    case RIGHT:
      return grid[j][i] < 2;
    case DOWN:
      return grid[j][i] % 2 == 0;
  }
}

function removeSpot(j, i, side) {
  if (exists(j, i, side)) grid[j][i] += side;
}