【p5.js】シェルピンスキーのカーペット

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

function draw() {
  background(220);
  drawSquare(50, 50, 300, 4);
}

function drawSquare(x, y, length, level) {
  fill(0);
  rect(x, y, length, length);
  if (level > 0) {
    fill(255);
    rect(x, y, length, length);
    length /= 3;
    drawSquare(x, y, length, level-1);
    drawSquare(x+length, y, length, level-1);
    drawSquare(x+length*2, y, length, level-1);
    drawSquare(x, y+length, length, level-1);
    drawSquare(x+length*2, y+length, length, level-1);
    drawSquare(x, y+length*2, length, level-1);
    drawSquare(x+length, y+length*2, length, level-1);
    drawSquare(x+length*2, y+length*2, length, level-1);
  }
}

今回は、以下のように出力される。