使用three.js显示多次相同的3D对象

我使用的是Three.js javascript库。为了测试它，我从这里下载了一个例子。

我试图使用for循环显示几次相同的元素。有两个问题相关(1,2)但这不是我想要的。我的问题是，如果我在循环中创建元素，它将只显示迭代的最后一个元素。在本例中，位置为(12,12)的元素

但是，如果我执行像alert这样的操作，它将显示所有元素。如果我有任何其他函数延迟执行。

我看到一些例子运行，如mrdoob的例子，但我希望这段代码运行，因为我需要加载几个网格，而不是生成原始图形。

// Set up the scene, camera, and renderer as global variables.
var scene, camera, renderer;
var group;
// Call functions
init();
animate();
// Sets up the scene.
function init() {
  // Iterator
  var i, j;
  // Create the scene and set the scene size.
  scene = new THREE.Scene();
  var WIDTH = window.innerWidth,
      HEIGHT = window.innerHeight;
  // Create a renderer and add it to the DOM.
  renderer = new THREE.WebGLRenderer({antialias:true});
  renderer.setSize(WIDTH, HEIGHT);
  document.body.appendChild(renderer.domElement);
  // Create a camera, zoom it out from the model a bit, and add it to the scene.
  camera = new THREE.PerspectiveCamera(45, WIDTH / HEIGHT, 0.1, 20000);
  camera.position.set(0,20,20);
  scene.add(camera);
  // Create an event listener that resizes the renderer with the browser window.
  window.addEventListener('resize', function() {
    var WIDTH = window.innerWidth,
        HEIGHT = window.innerHeight;
    renderer.setSize(WIDTH, HEIGHT);
    camera.aspect = WIDTH / HEIGHT;
    camera.updateProjectionMatrix();
  });
  // Set the background color of the scene.
  renderer.setClearColor(0x333F47, 1);
  // Create a light, set its position, and add it to the scene.
  var light = new THREE.PointLight(0xffffff);
  light.position.set(-100,200,100);
  scene.add(light);

  group = new THREE.Object3D();
  for(i=0; i < 15; i+=3) {
    for(j=0; j < 15; j+=3) {
      var loader = new THREE.JSONLoader();
      loader.load( "models/treehouse_logo.js", function(geometry){
        var material = new THREE.MeshLambertMaterial({color: 0x55B663});
        var mesh = new THREE.Mesh(geometry, material);
        mesh.position.set(i,0,j);
        group.add(mesh);
      });
    //alert("iteration"+i+" "+j);
    }
  }
  scene.add( group );
  // Add OrbitControls so that we can pan around with the mouse.
  controls = new THREE.OrbitControls(camera, renderer.domElement);
}
// Renders the scene and updates the render as needed.
function animate() {
  // Read more about requestAnimationFrame at http://www.paulirish.com/2011/requestanimationframe-for-smart-animating/
  requestAnimationFrame(animate);
  // Render the scene.
  renderer.render(scene, camera);
  controls.update();
}