var next;

​

function setup() {

  createCanvas(200, 200);

  frameRate(1000);

  pixelDensity(1);

  grid = [];

  next = [];

  for (var x = 0; x < width; x++) {

    grid[x] = [];

    next[x] = [];

    for (var y = 0; y < height; y++) {

      grid[x][y] = {

        a: 1,

        b: 0

      };

      next[x][y] = {

        a: 1,

        b: 0

      };

​

    }

  }

  for( var i = 100; i < 110; i++ ){

    for( var j = 100; j < 110; j++ ){

      grid[i][j].b = 1;

    }

  }

}

​

var dA = 1;

var dB = 0.5;

var feed = 0.055;

var k = 0.062;

​

function draw() {

  background(51);

​

  for (var x = 1; x < width - 1; x++) {

    for (var y = 1; y < height - 1; y++) {

      var a = grid[x][y].a;

      var b = grid[x][y].b;

      next[x][y].a = a + dA * laplaceA(x, y) - a * b * b + feed * (1 - a);

      next[x][y].b = b + dB * laplaceB(x, y) + a * b * b - (k + feed) * b;

​

      next[x][y].a = constrain(next[x][y].a, 0, 1);

      next[x][y].b = constrain(next[x][y].b, 0, 1);

    }

  }

​

  loadPixels();

  for (var x = 0; x < width; x++) {

    for (var y = 0; y < height; y++) {

      var pix = (x + y * width) * 4;

      var a = next[x][y].a;

      var b = next[x][y].b;

      var c = floor((a - b) * 255);

      c = constrain(c, 0, 255);

      pixels[pix + 0] = c;

      pixels[pix + 1] = c;

      pixels[pix + 2] = c;

      pixels[pix + 3] = 255;

    }

  }

  updatePixels();

​

  swap();

}

​

function laplaceA(x,y) {

  var sumA = 0;

  sumA += grid[x][y].a * -1;

  sumA += grid[x-1][y].a * 0.2;

  sumA += grid[x+1][y].a * 0.2;

  sumA += grid[x][y+1].a * 0.2;

  sumA += grid[x][y-1].a * 0.2;

  sumA += grid[x-1][y-1].a * 0.05;

  sumA += grid[x+1][y-1].a * 0.05;

  sumA += grid[x+1][y+1].a * 0.05;

  sumA += grid[x-1][y+1].a * 0.05;

  return sumA;

}

​

function laplaceB(x,y) {

  var sumB = 0;

  sumB += grid[x][y].b * (-1);

  sumB += grid[x-1][y].b * 0.2;

  sumB += grid[x+1][y].b * 0.2;

  sumB += grid[x][y+1].b * 0.2;

  sumB += grid[x][y-1].b * 0.2;

  sumB += grid[x-1][y-1].b * 0.05;

  sumB += grid[x+1][y-1].b * 0.05;

  sumB += grid[x+1][y+1].b * 0.05;

  sumB += grid[x-1][y+1].b * 0.05;

  return sumB;

}

​

function swap() {

  var temp = grid;

  grid = next;

  next = temp;

}