filter(ERODE)で削られていくリング

/**
 * eroded ring
 * 
 * @author aadebdeb
 * @date 2017/02/27
 */

var particles;

function setup() {
  createCanvas(500, 300);
  frameRate(3);

  particles = [];
  for (var i = 0; i < 1000; i++) {
    particles.push(new Particle());
  }
  
  background(0);
  noStroke();
}

function draw() {
  translate(width / 2, height / 2);
  fill(lerpColor(color(249, 231, 40), color(111, 186, 44), map(sin(frameCount * 0.1), -1, 1, 0, 1)));
  for (var i = 0; i < particles.length; i++) {
    var particle = particles[i];
    particle.render();
  }
  filter(ERODE);

}

function Particle() {
  this.posAng = random(TWO_PI);
  this.posXAng = random(TWO_PI);
  this.posYAng = random(TWO_PI);
  this.sizeAng = random(TWO_PI);
}

Particle.prototype = {
  render: function() {
    var size = map(sin(frameCount * 0.023 + this.sizeAng), -1, 1, 2, 5);
    var x = map(sin(frameCount * 0.01 + this.posXAng), -1, 1, 130, 220);
    var y = map(sin(frameCount * 0.01 + this.posYAng), -1, 1, 50, 100) * map(sin(frameCount * 0.07), -1, 1, -1, 1);
    ellipse(x * cos(-frameCount * 0.043 + this.posAng), y * sin(-frameCount * 0.043 + this.posAng), size, size);
  },
}