// Coding in the Cabana

// The Coding Train / Daniel Shiffman

// https://thecodingtrain.com/CodingInTheCabana/003-hilbert-curve.html

// https://youtu.be/dSK-MW-zuAc

​

const order = 8;

let N;

let total;

​

let path = [];

​

let counter = 0;

​

function setup() {

  createCanvas(512, 512);

  colorMode(HSB, 360, 255, 255);

  background(0);

​

  N = int(pow(2, order));

  total = N * N;

​

  for (let i = 0; i < total; i++) {

    path[i] = hilbert(i);

    let len = width / N;

    path[i].mult(len);

    path[i].add(len / 2, len / 2);

  }

}

​

function draw() {

  background(0);

​

  stroke(255);

  strokeWeight(1);

  noFill();

  //beginShape();

  for (let i = 1; i < counter; i++) {

    let h = map(sin(i), 0, path.length, 0, 360);

    stroke(h, 255, 255);

    line(path[i].x, path[i].y, path[i - 1].x, path[i - 1].y);

  }

  //endShape();

​

  counter += 50;

  if (counter >= path.length) {

    counter = 0;

  }

​

  // strokeWeight(4);

  // for (let i = 0; i < path.length; i++) {

  //  point(path[i].x, path[i].y);

  //  text(i, path[i].x+5, path[i].y);

  // }

}

​

​

function hilbert(i) {

  const points = [

    new p5.Vector(0, 0),

    new p5.Vector(0, 1),

    new p5.Vector(1, 1),

    new p5.Vector(1, 0)

  ];

​

  let index = i & 3;

  let v = points[index];

​

  for (let j = 1; j < order; j++) {

    i = i >>> 2;

    index = i & 3;

    let len = pow(2, j);

    if (index == 0) {

      let temp = v.x;

      v.x = v.y;

      v.y = temp;

    } else if (index == 1) {

      v.y += len;

    } else if (index == 2) {

      v.x += len;

      v.y += len;

    } else if (index == 3) {

      let temp = len - 1 - v.x;

      v.x = len - 1 - v.y;

      v.y = temp;

      v.x += len;

    }

  }

  return v;

}