​

function setup() {

  createCanvas(640, 480);

  angleMode(DEGREES);

  initializeFlock(100);

}

​

function draw() {

  background(220);

​

  renderFlock();

  updateFlock();

}

​

// Boid

​

class Boid {

  constructor() {

    const theta = random(0, 360);

​

    this.uniqueid = uid();

    this.position = createVector(random(width), random(height));

    this.velocity = createVector(speed * cos(theta), speed * sin(theta));

  }

​

  update() {

    this.velocity

      .add(cohesion(this))

      .add(alignment(this))

      .add(separation(this))

      .limit(speed);

​

    this.position

      .add(this.velocity);

​

    // Wrap around if the boid overshoots the canvas.

    if (this.position.y < 0) this.position.y = height;

    else if (this.position.y > height) this.position.y = 0;

​

    if (this.position.x < 0) this.position.x = width;

    else if (this.position.x > width) this.position.x = 0;

  }

​

  render() {

    push();

​

    translate(this.position.x, this.position.y);

    rotate(this.velocity.heading());

​

    stroke(150);

    strokeWeight(1);

    noFill(120);

    beginShape();

    vertex(10, 0);

    vertex(-5, -5);

    vertex(-2, 0);

    vertex(-5, 5);

    endShape(CLOSE);

​

    pop();

  }

​

  equals(other) {

    return this.uniqueid === other.uniqueid;

  }

​

  distance(other) {

    return this.position.dist(other.position);

  }

​

  displacement(other) {

    return p5.Vector.sub(other.position, this.position);

  }

}

​

// Flock

​

// Stores and array of boids.

let flock = [];

​

// Make a flock of n boids.

// Updates the global `flock` variable.

function initializeFlock(n = 10) {

  flock = [];

  for (let i = 0; i < n; i++) {

    flock[i] = new Boid();

  }

}

​

// Draw one frame of the flock.

// Delegates to `Boid.render`.

function renderFlock() {

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

    flock[i].render();

  }

}

​

// Update all boids in the flock.

// Delegates to `Boid.update`.

function updateFlock() {

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

    flock[i].update();

  }

}

​

// Steering behaviors.

​

// Cohesion: Each boid moves towards the

// average center of the flock.

function cohesion(boid) {

  let cohesionVector = createVector(0, 0);

​

  const neighbours = getNeighbours(boid);

  const averagePosition = getAveragePosition(neighbours);

​

  if (neighbours.length != 0) {

    cohesionVector =

      averagePosition

      .sub(boid.position)

      .div(10000);

  }

​

  return cohesionVector;

}

​

// Alignment: Each boid aligns its velocity

// with the average velocity of the flock.

function alignment(boid) {

  let alignmentVector = createVector(0, 0);

​

  const neighbours = getNeighbours(boid);

  const averageVelocity = getAverageVelocity(neighbours);

​

  if (neighbours.length != 0) {

    alignmentVector =

      averageVelocity

      .sub(boid.velocity)

      .div(100);

  }

​

  return alignmentVector;

}

​

// Separation: Each boid keeps a small distance

// away from the rest of the flock.

function separation(boid) {

  let separationVector = createVector(0, 0);

​

  const neighbours = getNeighbours(boid);

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

    if (boid.distance(neighbours[i]) < 20)

      separationVector.sub(boid.displacement(neighbours[i]));

  }

​

  return separationVector.div(100);

}

​

function getNeighbours(boid) {

  let neighbours = [];

  for (var i = 0; i < flock.length; i++) {

    if (!boid.equals(flock[i]) && boid.distance(flock[i]) < 100)

      neighbours.push(flock[i])

  }

  return neighbours;

}

​

function getAveragePosition(boids) {

  let averagePosition = createVector(0, 0);

  for (var i = 0; i < boids.length; i++) {

    averagePosition.add(boids[i].position);

  }

  averagePosition.div(boids.length || 1);

  return averagePosition;

}

​

function getAverageVelocity(boids) {

  let averageVelocity = createVector(0, 0);

  for (var i = 0; i < boids.length; i++) {

    averageVelocity.add(boids[i].velocity)

  }

  averageVelocity.div(boids.length || 1);

  return averageVelocity;

}

​

// Utils

​

// Generate a unique id of given length (default to 7).

function uid(len = 7) {

  return Math.random().toString(35).substr(2, len);

}