title: Displacement map on BoxGeometry only moves edges?
body: <p>I'm just starting to get my bearings with threejs and I'm having an issue using Displacement Maps. </p>
  
  <p><a href="http://codepen.io/jpschwinghamer/pen/BWPebJ" rel="nofollow noreferrer">http://codepen.io/jpschwinghamer/pen/BWPebJ</a></p>
  
  <p>I have a simple BoxGeometry that I'm trying to apply textures to a phong material. All seem to work correctly except for the displacement map. I made sure to add segments to the BoxGeometry instantiation. Is there some bit of magic that I'm missing to make my displacement map work correctly?</p>
  
  <p>Consider this code:</p>
  
  <pre><code>  var animate, camera, displacement, geometry, light, light1, map, material, mesh, normal, reflection, renderer, roughness, textureLoader;
  
    renderer = new THREE.WebGLRenderer({
      canvas: document.querySelector('canvas'),
      antialiased: true
    });
  
    renderer.setClearColor(0xfff000);
  
    renderer.setSize(window.innerWidth, window.innerHeight);
  
    renderer.setPixelRatio(window.devicePixelRatio);
  
    camera = new THREE.PerspectiveCamera(35, window.innerWidth / window.innerHeight, 0.1, 3000);
  
    window.scene = new THREE.Scene();
  
    light = new THREE.AmbientLight(0xffffff, 0.5);
  
    scene.add(light);
  
    light1 = new THREE.PointLight(0xffffff, 0.6);
  
    scene.add(light1);
  
    textureLoader = new THREE.TextureLoader();
  
    textureLoader.setCrossOrigin("anonymous");
  
    map = textureLoader.load("https://s3-us-west-2.amazonaws.com/s.cdpn.io/65874/WoodFlooring044_COL_2K.jpg");
    normal = textureLoader.load("https://s3-us-west-2.amazonaws.com/s.cdpn.io/65874/WoodFlooring044_NRM_2K.jpg");
    roughness = textureLoader.load("https://s3-us-west-2.amazonaws.com/s.cdpn.io/65874/WoodFlooring044_GLOSS_2K.jpg");
    reflection = textureLoader.load("https://s3-us-west-2.amazonaws.com/s.cdpn.io/65874/WoodFlooring044_REFL_2K.jpg");
    displacement = textureLoader.load("https://s3-us-west-2.amazonaws.com/s.cdpn.io/65874/WoodFlooring044_DISP_2K.jpg");
  
    geometry = new THREE.BoxGeometry(100, 100, 100, 10, 10, 10);
  
    material = new THREE.MeshPhongMaterial({
      map: map,
      normalMap: normal,
      normalScale: new THREE.Vector2(30, -1),
      roughnessMap: roughness,
      reflectionMap: reflection,
      displacementMap: displacement,
      displacementScale: 1,
      displacementBias: 0
    });
  
    mesh = new THREE.Mesh(geometry, material);
  
    mesh.position.set(0, 0, -700);
  
    scene.add(mesh);
  
    animate = function() {
      mesh.rotation.x += 0.01;
      mesh.rotation.y += 0.01;
      requestAnimationFrame(animate);
      return renderer.render(scene, camera);
    };
  
    animate();
  </code></pre>