javascript - three.jsでパーティクルを回転させる方法

Question

画像である粒子があります。パーティクルを回転させると、後ろに円が残ります。この奇妙な円を取り除くにはどうすればよいですか?

フィドルはこちら: http://jsfiddle.net/zUvsp/137/

コード：

var camera, scene, renderer, material, img, texture, particle;
init();
animate();

function init() {
  scene = new THREE.Scene();
  camera = new THREE.PerspectiveCamera(50, window.innerWidth / window.innerHeight, 1, 10000);
  camera.position.z = 1000;
  scene.add(camera);

  img = new Image();
  texture = new THREE.Texture(img);

  img.onload = function() {
    texture.needsUpdate = true;
    makeParticle();
  };
  img.src = "http://www.atalasoft.com/cs/blogs/davidcilley/files/PNG_Mask.png";

  renderer = new THREE.CanvasRenderer();
  renderer.setSize(window.innerWidth, window.innerHeight);
  document.body.appendChild(renderer.domElement);
}

function makeParticle() {
  material = new THREE.ParticleBasicMaterial({
    map: texture,
    blending: THREE.AdditiveBlending,
  });
  // make the particle
  particle = new THREE.Particle(material);
  particle.scale.x = particle.scale.y = 1;
  particle.position.x = 10;
  scene.add(particle);
}

function animate() {
  requestAnimationFrame(animate);
  renderer.render(scene, camera);
  particle.rotation.z += 0.01
}