【作品No.28】ジュリア集合【p5.js 2025年1月27日】

function setup() {
  createCanvas(600, 600);
  pixelDensity(1);
}

function draw() {
  loadPixels();
  let maxIterations = 100;

  for (let x = 0; x < width; x++) {
    for (let y = 0; y < height; y++) {
      let a = map(x, 0, width, -1.5, 1.5);
      let b = map(y, 0, height, -1.5, 1.5);

      let ca = 0.355;
      let cb = 0.355;
      let n = 0;

      while (n < maxIterations) {
        let aa = a * a - b * b;
        let bb = 2 * a * b;
        a = aa + ca;
        b = bb + cb;

        if (abs(a + b) > 16) {
          break;
        }
        n++;
      }

      let bright = map(n, 0, maxIterations, 0, 255);

      if (n === maxIterations) {
        bright = 0;
      }

      let pix = (x + y * width) * 4;
      pixels[pix + 0] = bright;
      pixels[pix + 1] = bright;
      pixels[pix + 2] = bright;
      pixels[pix + 3] = 255;
    }
  }
  updatePixels();

}