title: Three.js: Convert face normal from local space to world space
body: <p>I have a <code>THREE.PlaneGeometry</code>, with <code>ComputeFaceNormals()</code>. I create two meshes using this geometry, with different rotations applied to them. I want to compute the two angles between the camera and the two meshes central face normal. It should be :</p>
  
  <pre><code>vLocalCamera = vCamera.position - mesh1.position;
  
  mesh1.normal() . vLocalCamera = cos(angle);
  </code></pre>
  
  <p>The problem is that I don't know how to get the mesh normal in world coordinate (from geometry and mesh rotation) with three.js API</p>