title: what is the use of computeFaceNormals, computeVertexNormals and computeMorphNormals
body: <p>What are the uses of <code>computeFaceNormals(), computeVertexNormals() and computeMorphNormals()</code>.</p>
  
  <p>I commented the <code>geometry.computeVertexNormals()</code> in an example and the model was appearing like it was given flat shading. when i added <code>geometry.computeVertexNormals()</code> the model was appearing like it was given smooth shading. Is this the uses <code>geometry.computeVertexNormals()</code> ?</p>