​

var num = 2000;

var noiseScale=500, noiseStrength=1;

var particles = [num];

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  noStroke();

  for (let i=0; i<num; i++) {

    //x value start slightly outside the right of canvas, z value how close to viewer

    var loc = createVector(random(width*1.2), random(height), 2);

    var angle = 0; //any value to initialize

    var dir = createVector(cos(angle), sin(angle));

    var speed = random(0.5,2);

    // var speed = random(5,map(mouseX,0,width,5,20));   // faster

    particles[i]= new Particle(loc, dir, speed);

  }

}

​

function windowResized() {

  resizeCanvas(windowWidth, windowHeight);

}

function draw() {

  // background(0);

  fill(0, 10);

​

  rect(0, 0, width, height);

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

    particles[i].run();

  }

}

​

class Particle{

  constructor(_loc,_dir,_speed){

    this.loc = _loc;

    this.dir = _dir;

    this.speed = _speed;

    // var col;

  }

  run() {

    this.move();

    this.checkEdges();

    this.update();

  }

  move(){

    let angle=noise(this.loc.x/noiseScale, this.loc.y/noiseScale, frameCount/noiseScale)*TWO_PI*noiseStrength; //0-2PI

    this.dir.x = cos(angle);

    this.dir.y = sin(angle);

    var vel = this.dir.copy();

    var d =1;  //direction change 

    vel.mult(this.speed*d); //vel = vel * (speed*d)

    this.loc.add(vel); //loc = loc + vel

  }

  checkEdges(){

    //float distance = dist(width/2, height/2, loc.x, loc.y);

    //if (distance>150) {

    if (this.loc.x<0 || this.loc.x>width || this.loc.y<0 || this.loc.y>height) {    

      this.loc.x = random(width*1.2);

      this.loc.y = random(height);

    }

  }

  update(){

    fill(255);

    ellipse(this.loc.x, this.loc.y, this.loc.z);

  }

}