​

let buffer1;

let buffer2;

let cooling;

const w = 300;

const h = 200;

​

let ystart = 0.0;

​

function setup() {

  pixelDensity(1);

  createCanvas(w * 2, h);

  buffer1 = createGraphics(w, h);

  buffer2 = createGraphics(w, h);

  cooling = createImage(w, h);

}

​

function cool() {

  cooling.loadPixels();

  let xoff = 0.0; // Start xoff at 0

  let increment = 0.02;

  // For every x,y coordinate in a 2D space, calculate a noise value and produce a brightness value

  for (let x = 0; x < w; x++) {

    xoff += increment; // Increment xoff

    let yoff = ystart; // For every xoff, start yoff at 0

    for (let y = 0; y < h; y++) {

      yoff += increment; // Increment yoff

​

      // Calculate noise and scale by 255

      let n = noise(xoff, yoff);

      let bright = pow(n, 3) * 255;

​

      // Try using this line instead

      //float bright = random(0,255);

​

      // Set each pixel onscreen to a grayscale value

      let index = (x + y * w) * 4;

      cooling.pixels[index] = bright;

      cooling.pixels[index + 1] = bright;

      cooling.pixels[index + 2] = bright;

      cooling.pixels[index + 3] = 255;

    }

  }

​

  cooling.updatePixels();

  ystart += increment;

}

​

function fire(rows) {

  buffer1.loadPixels();

  for (let x = 0; x < w; x++) {

    for (let j = 0; j < rows; j++) {

      let y = h - (j + 1);

      let index = (x + y * w) * 4;

      buffer1.pixels[index] = 255;

      buffer1.pixels[index + 1] = 255;

      buffer1.pixels[index + 2] = 255;

      buffer1.pixels[index + 3] = 255;

    }

  }

  buffer1.updatePixels();

}

​

function draw() {

  fire(2);

  if (mouseIsPressed) {

    buffer1.fill(255);

    buffer1.noStroke();

    buffer1.ellipse(mouseX, mouseY, 100, 100);

  }

  cool();

  background(0);

  buffer1.loadPixels();

  buffer2.loadPixels();

  for (let x = 1; x < w - 1; x++) {

    for (let y = 1; y < h - 1; y++) {

      let index0 = (x + y * w) * 4; // x, y

      let index1 = (x + 1 + y * w) * 4; // (x + 1), y

      let index2 = (x - 1 + y * w) * 4; // (x - 1), y

      let index3 = (x + (y + 1) * w) * 4; // x, (y + 1)

      let index4 = (x + (y - 1) * w) * 4; // x, (y - 1)

​

      // Because we are using only gray colors, the value of the color

      // components are the same, and we can use that as brightness.

      let c1 = buffer1.pixels[index1];

      let c2 = buffer1.pixels[index2];

      let c3 = buffer1.pixels[index3];

      let c4 = buffer1.pixels[index4];

​

      let c5 = cooling.pixels[index0];

      let newC = c1 + c2 + c3 + c4;

      newC = newC * 0.25 - c5;

​

      buffer2.pixels[index4] = newC;

      buffer2.pixels[index4 + 1] = newC;

      buffer2.pixels[index4 + 2] = newC;

      buffer2.pixels[index4 + 3] = 255;

    }

  }

  buffer2.updatePixels();

​

  // Swap

  let temp = buffer1;

  buffer1 = buffer2;

  buffer2 = temp;

​

  image(buffer2, 0, 0);

  image(cooling, w, 0);

}