// Daniel Shiffman

// http://natureofcode.com

​

let particles = [];

​

// Making sure pairs of particles are not checked twice

let checkedPairs = new Set();

let palette = [

  [11, 106, 136],

  [45, 197, 244],

  [112, 50, 126],

  [146, 83, 161],

  [164, 41, 99],

  [236, 1, 90],

  [240, 99, 164],

  [241, 97, 100],

  [248, 158, 79],

  [252, 238, 33],

];

​

function setup() {

  createCanvas(640, 640);

  for (let i = 0; i < 1500; i++) {

    let x = random(width);

    let y = random(height);

    let mass = random(4, 8);

    particles.push(new Particle(x, y, mass, i));

  }

}

​

function draw() {

  background(0);

​

  // Create a quadtree

  let boundary = new Rectangle(width / 2, height / 2, width, height);

  let qtree = new QuadTree(boundary, 4);

  checkedPairs.clear();

​

  // Insert all particles

  for (let particle of particles) {

    let point = new Point(particle.position.x, particle.position.y, particle);

    qtree.insert(point);

  }

​

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

    let particleA = particles[i];

    let range = new Circle(

      particleA.position.x,

      particleA.position.y,

      particleA.r * 2

    );

​

    // Check only nearby particles based on quadtree

    let points = qtree.query(range);

    for (let point of points) {

      let particleB = point.userData;

      if (particleB !== particleA) {

        let idA = particleA.id;

        let idB = particleB.id;

        let pair = idA < idB ? `${idA},${idB}` : `${idB},${idA}`;

        if (!checkedPairs.has(pair)) {

          particleA.collide(particleB);

          checkedPairs.add(pair);

        }

      }

    }

  }

​

  for (let particle of particles) {

    particle.update();

    particle.edges();

    particle.show();

  }

​

  if (frameCount % 120 == 0) {

    console.log(frameRate());

  }

}

​