var nParticles = 150;

​

function setup() {

  createCanvas(400, 400);

  initParticles();

}

​

function draw() {

  background(200);

​

  var nsc = 0.01; // noise scale

  for (var y = 0; y <= height; y += 10) {

    for (var x = 0; x <= width; x += 10) {

      var fx = noise(1 + x * nsc, 5 + y * nsc) - 0.5;

      var fy = noise(9 + x * nsc, 7 + y * nsc) - 0.5;

      line(x, y, x + 50 * fx, y + 50 * fy);

    }

  }

​

  var fieldStrength = 1.0;

  for (var i = 0; i < nParticles; i++) {

    var x = myParticles[i].px;

    var y = myParticles[i].py;

​

    var fx = fieldStrength * (noise(1 + x * nsc, 5 + y * nsc) - 0.5);

    var fy = fieldStrength * (noise(9 + x * nsc, 7 + y * nsc) - 0.5);

​

    myParticles[i].impel(fx, fy);

    myParticles[i].update();

    myParticles[i].render();

  }

}

​

function mousePressed() {

  initParticles();

}

​

function initParticles() {

  noiseSeed(millis());

  myParticles = [];

  for (var i = 0; i < nParticles; i++) {

    var rx = random(width * 0.05, width * 0.95);

    var ry = random(width * 0.05, width * 0.95);

    myParticles.push(new Particle(rx, ry, 0, 0));

  }

}

​

​

​

​

​

//----------------------------------------

class Particle {

  constructor(inpx, inpy, invx, invy) {

    this.mass = 1.0;

    this.FRICTION = 0.95;

    this.px = inpx;

    this.py = inpy;

    this.vx = invx;

    this.vy = invy;

  }

​

  impel(fx, fy) {

    // Add an acceleration (a = F/m)

    this.vx += fx / this.mass;

    this.vy += fy / this.mass;

  }

​

  update() {

    // Euler integration

    this.vx *= this.FRICTION;

    this.vy *= this.FRICTION;

    this.px += this.vx;

    this.py += this.vy;

  }

​

  render() {

    ellipse(this.px, this.py, 20, 20);

  }

}