title: Using threeGLTFLoader load gltf get transparency problem
body: <p>I try to use threeGLTFLoader to load gltf ,problem with the material,the model is a man’s head but now i could see the back
  here is the code:</p>
  
  <pre><code>var threeGLTFLoader = new THREE.GLTFLoader();
  
  var objPositions;
  
  threeGLTFLoader.load("../resources/untitled.gltf", function (gltf) {
      model = gltf.scene;
      model.name = "man";
      model.scale.set(300, 300, 300);
      root.matrixAutoUpdate = false;
      root.updateMatrix();
      root.add(model);
  });
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/rKIFc.png" alt="enter image description here"></p>
  
  <p><a href="https://i.stack.imgur.com/RY2fj.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RY2fj.jpg" alt="enter image description here"></a></p>
  
  <p>The link of <a href="https://sketchfab.com/3d-models/kolya-477d20161e224255abc6275f784a8056" rel="nofollow noreferrer">3D model</a></p>