Moonlight landscape

// Sketch inspired by sketch from @KilledByAPixel at https://dwitter.net/d/26198

​

let angle_increment = 0;

let shine_frequency = 0;

let birds_travel_length = 0;

​

function setup() {

  createCanvas(1080, 720);

  background(0);

  tree_image = createGraphics(width, height);

  tree_image.fill(0);

  tree_recursion(500, height, 40, -0.2);

  tree_recursion(500, 720, 50, 0.6);

  tree_recursion(900, 720, 50, 0.6);

  strokeWeight(3);

}

​

function draw() {

  shine_frequency += 4;

  birds_travel_length += 2;

  if (birds_travel_length > 1100) birds_travel_length = 0;

  noStroke();

  for (i = 0; i < 30; i++) {

    rays_color = 255 * (i / 29);

    z = i * 40 - (shine_frequency % 40);

    let rays_radius = 3.5 * height * (1 - z / (99 + z));

    circle(400, 200, rays_radius);

    fill(rays_color);

  }

  image(tree_image, 0, 0);

  noFill();

  stroke(0);

  for (y = 80; y < 200; y += 40) {

    for (x = width; x -= 40;) {

      draw_bird((y + birds_travel_length) % 1100, (width - ((y + birds_travel_length) % width / 4)) - 800, 15);

    }

  }

}

​

function calculate_angle_increment() {

  return angle_increment = sin((angle_increment - 11) ** 9);

}

​

function tree_recursion(x, y, radius, angle) {

  if (radius > 1) {

    let angle_increment = calculate_angle_increment();

    tree_image.circle(x, y, radius);

    tree_recursion(

      x - (sin(angle) * radius) / 2,

      y - (cos(angle) * radius) / 2,

      radius * 0.985,

      angle + angle_increment / 4

    );

    if (angle_increment > 0.94) {

      tree_recursion(x, y, radius * 0.5, angle_increment * 0.5);

    }

  }

}

​

function draw_bird(a, c, d) {

  b = sin(a / 6) * d + c;

  bezier(a, c + d, a, c, a + d, c, a + 2 * d, b);

  bezier(a, c + d, a, c, a - d, c, a - 2 * d, b);

}