reaction-diffusion.js

// Based on Shiffman's Reaction Diffusion Tut: https://youtu.be/Cl_Gjj80gPE
//
// Changed to simulate once, on startup
// Then draw the lines of the resulting chains
// Will need to update vector to Victor.js in order to use with plotter

var tree = [];
var walkers = [];
var maxWalkers = 40;
var iterations = 1000;
var radius = 8;
var hu = 0;
var shrink = 0.995;
var stuckCount = 0;
var drawingComplete = false;

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

  tree[0] = new Walker(width / 2, height / 2);
  tree[0].isRoot = true;
  radius *= shrink;
  for (var i = 0; i < maxWalkers; i++) {
    walkers[i] = new Walker();
    radius *= shrink;
  }

  while(!drawingComplete){
      for (var n = 0; n < iterations; n++) {
        for (var i = walkers.length - 1; i >= 0; i--) {
          walkers[i].walk();
          if (walkers[i].checkStuck(tree)) {
              stuckCount++;
              if(stuckCount == 414){
                // por que 414 ??
                drawingComplete = true;
              }


            walkers[i].setHue(hu % 360);
            hu += 2;
            tree.push(walkers[i]);
            walkers.splice(i, 1);
          }
        }
      }

      //var r = walkers[walkers.length - 1].r;
      while (walkers.length < maxWalkers && radius > 1) {
        radius *= shrink;
        walkers.push(new Walker());
      }
  } // while !drawingComplete

  noFill();
  stroke(0);
  for(let i=0; i < tree.length; i++){
      DrawBranch(tree[i]);
  }


}


function DrawBranch(seed){
    if(!seed.linkedTo) return;
    line(seed.pos.x, seed.pos.y, seed.linkedTo.pos.x, seed.linkedTo.pos.y);
    DrawBranch(seed.linkedTo);
}

// Walker Object
function Walker(x, y) {
    this.isRoot = false;
    this.linkedTo = false;
  if (arguments.length == 2) {
    this.pos = createVector(x, y);
    this.stuck = true;
  } else {
    this.pos = randomPoint();
    this.stuck = false;
  }
  this.r = radius;


  this.walk = function() {
    var vel = p5.Vector.random2D();
    // var vel = createVector(random(-1, 1), random(-0.5, 1));
    this.pos.add(vel);
    this.pos.x = constrain(this.pos.x, 0, width);
    this.pos.y = constrain(this.pos.y, 0, height);
  }


  this.checkStuck = function(others) {
    for (var i = 0; i < others.length; i++) {
      var d = distSq(this.pos, others[i].pos);
      if (d < (this.r * this.r + others[i].r * others[i].r +  2 * others[i].r * this.r)) {
        //if (random(1) < 0.1) {
        this.linkedTo = others[i];
        this.stuck = true;
        return true;
        break;
        //}
      }
    }
    return false;
  }


}

function randomPoint() {
  var i = floor(random(4));

  if (i === 0) {
    var x = random(width);
    return createVector(x, 0);
  } else if (i === 1) {
    var x = random(width);
    return createVector(x, height);
  } else if (i === 2) {
    var y = random(height);
    return createVector(0, y);
  } else {
    var y = random(height);
    return createVector(width, y);
  }
}


function distSq(a, b) {
  var dx = b.x - a.x;
  var dy = b.y - a.y;
  return dx * dx + dy * dy;
}