// This will contain the pixels used to calculate the fire effect
  int[][] fire;
  
  // Flame colors
  color[] palette;
  float angle;
  int[] calc1,calc2,calc3,calc4,calc5;
  
  PGraphics pg;
  
  void setup(){
    size(640, 360, P3D);
    
    // Create buffered image for 3d cube
    pg = createGraphics(width, height, P3D);
  
    calc1 = new int[width];
    calc3 = new int[width];
    calc4 = new int[width];
    calc2 = new int[height];
    calc5 = new int[height];
  
    colorMode(HSB);
  
    fire = new int[width][height];
    palette = new color[255];
  
    // Generate the palette
    for(int x = 0; x < palette.length; x++) {
      //Hue goes from 0 to 85: red to yellow
      //Saturation is always the maximum: 255
      //Lightness is 0..255 for x=0..128, and 255 for x=128..255
      palette[x] = color(x/3, 255, constrain(x*3, 0, 255));
    }
  
    // Precalculate which pixel values to add during animation loop
    // this speeds up the effect by 10fps
    for (int x = 0; x < width; x++) {
      calc1[x] = x % width;
      calc3[x] = (x - 1 + width) % width;
      calc4[x] = (x + 1) % width;
    }
    
    for(int y = 0; y < height; y++) {
      calc2[y] = (y + 1) % height;
      calc5[y] = (y + 2) % height;
    }
  }
  
  void draw() {
    angle = angle + 0.05;
  
    // Rotating wireframe cube
    pg.beginDraw();
    pg.translate(width >> 1, height >> 1);
    pg.rotateX(sin(angle/2));
    pg.rotateY(cos(angle/2));
    pg.background(0);
    pg.stroke(128);
    pg.scale(25);
    pg.noFill();
    pg.box(4);
    pg.endDraw();
  
    // Randomize the bottom row of the fire buffer
    for(int x = 0; x < width; x++)
    {
      fire[x][height-1] = int(random(0,190)) ;
    }
  
    loadPixels();
  
    int counter = 0;
    // Do the fire calculations for every pixel, from top to bottom
    for (int y = 0; y < height; y++) {
      for(int x = 0; x < width; x++) {
        // Add pixel values around current pixel
  
        fire[x][y] =
            ((fire[calc3[x]][calc2[y]]
            + fire[calc1[x]][calc2[y]]
            + fire[calc4[x]][calc2[y]]
            + fire[calc1[x]][calc5[y]]) << 5) / 129;
  
        // Output everything to screen using our palette colors
        pixels[counter] = palette[fire[x][y]];
  
        // Extract the red value using right shift and bit mask 
        // equivalent of red(pg.pixels[x+y*w])
        if ((pg.pixels[counter++] >> 16 & 0xFF) == 128) {
          // Only map 3D cube 'lit' pixels onto fire array needed for next frame
          fire[x][y] = 128;
        }
      }
    }
    updatePixels();
  }