title: Get size of Object3D in Three.js
body: <p>I have this 3D object in my scene:</p>
  
  <pre><code>var icon = new THREE.Object3D()
  
  var iconTexture = THREE.ImageUtils.loadTexture('images/icon.png'),
        iconMaterial = new THREE.SpriteMaterial({
        map: iconTexture,
        color: 0xffffff,
        opacity: 1
  });
  
  var iconSprite = new THREE.Sprite(iconMaterial);
  
  iconSprite.scale.set(14, 14, 1.0);
  iconSprite.position.set(Math.random() - 0.5, Math.random() - 0.5, Math.random() - 0.75);
  
  icon.position.setLength(0);
  
  icon.add(iconSprite);
  
  icon.position.y = 15;
  icon.position.z = 20;
  scene.add(icon);
  scene.updateMatrixWorld(true);
  </code></pre>
  
  <p>I manged to get the position of this object:</p>
  
  <pre><code>var position = new THREE.Vector3();
  position.getPositionFromMatrix( icon.matrixWorld );
  console.log(position.x + ',' + position.y + ',' + position.z);
  </code></pre>
  
  <p>But I can't get the size of that object. I tried something like that:</p>
  
  <pre><code>console.log("sizes: "+icon.min+", "+icon.max);
  </code></pre>
  
  <p>But got this output: <code>sizes: undefined, undefined</code>.</p>
  
  <p>Is there any way to get the size of that object?</p>