// https://editor.p5js.org/codingtrain/sketches/XpS9wGkbB

// https://medium.com/@jason.webb/simulating-dla-in-js-f1914eb04b1d

​

let off;

​

let trees = [];

let walkers = [];

let grid;

const start_radius = 4;

const shrink = 0.995;

let radius;

let iterations = 1000;

let maxWalkers = 50;

function setup() {

  createCanvas(800, 800);

  background(20);

​

  radius = start_radius;

  off = width * 0.1;

​

  let x = off;

​

  noStroke();

  fill(color(0, 0, 40));

  rect(0, 0, off, height);

  fill(color(0, 0, 220));

  rect(off, 0, width - 2 * off, height);

  fill(color(0, 0, 80));

  rect(width - off, 0, off, height);

​

  stroke(220);

  for (let y = 2 * off; y < height; y += off / 2) {

    line(0, y, x, y - off);

    line(x, y - off, width - off, y - off);

    line(width - off, y - off, width, y - 2 * off);

​

    // if (random() > 0.2 && start_pts.length < 50) {

    let _x = random(x, width - off);

    let _y = y - off;

    trees.push([

      {

        pos: createVector(_x, _y),

        // x: _x,

        // y: _y,

        radius: start_radius,

      },

    ]);

    // }

  }

​

  fill(220);

  noStroke();

  for (let t of trees) {

    circle(t[0].pos.x, t[0].pos.y, t[0].radius * 2);

  }

​

  radius *= shrink;

  for (let i = 0; i < maxWalkers; i++) {

    walkers.push(new Walker());

    radius *= shrink;

  }

}

​

function draw() {

  for (let n = 0; n < iterations; n++) {

    for (let i = walkers.length - 1; i >= 0; i--) {

      let w = walkers[i];

​

      // walk

      w.walk();

​

      // check stuck

      let tree = w.checkStuck(trees);

      if (tree != null) {

        tree.push({ pos: createVector(w.pos.x, w.pos.y), radius: w.radius });

        circle(w.pos.x, w.pos.y, w.radius * 2);

        walkers.splice(i, 1);

      }

      // draw on tree if stuck and splice

    }

  }

​

  if (walkers.length == 0) {

    console.log("done");

    noLoop();

  } else {

    let r = walkers[walkers.length - 1].radius;

    while (walkers.length < maxWalkers && radius > 1) {

      radius *= shrink;

      walkers.push(new Walker());

    }

  }

}

​

class Walker {

  constructor(x, y) {

    if (arguments.length == 2) {

      this.pos = createVector(x, y);

      this.stuck = true;

    } else {

      // let xs = [];

      // for  (let t of tree) xs.push(t.pos.x);

      this.pos = createVector(random(width),random(height));

      // let x = random(xs);

      // x += random(-5,5);

      // this.pos = createVector(x, random(height));

​

      this.stuck = false;

    }

    this.radius = radius;

  }

​

  walk() {

    let vel = p5.Vector.random2D();

    this.pos.add(vel);

    this.pos.x = constrain(this.pos.x, 0, width);

    this.pos.y = constrain(this.pos.y, 0, height);

  }

​

  checkStuck(others) {

    for (let o of others) {

      for (let o2 of o) {

        let d = distSquared(this.pos, o2.pos);

        if (

          d <

          this.radius * this.radius +

            o2.radius * o2.radius +

            2 * o2.radius * this.radius

        ) {

          this.stuck = true;

          return o;

        }

      }

    }

    return null;

  }

}

​

function distSquared(a, b) {

  // console.log(a,b)

  let dx = b.x - a.x;

  let dy = b.y - a.y;

  return dx * dx + dy * dy;

}

​