title: computeVertexNormals
body: <p>I am using 3d modifiers <a href="https://github.com/foo123/MOD3" rel="noreferrer">https://github.com/foo123/MOD3</a> to bend a cube. After the geometry is updated (vertex positions are changed) the lights are not updated, the cube is still shaded as if nothing changed.
  So I tried </p>
  
  <p><code>cube.geometry.computeVertexNormals()</code></p>
  
  <p>and </p>
  
  <p><code>cube.geometry.computeFaceNormals()</code> </p>
  
  <p>but after that the cube is not rendered like a cube anymore but like an "ugly sphere":</p>
  
  <p><img src="https://i.stack.imgur.com/Wrerl.jpg" alt="enter image description here"></p>
  
  <p>On the left is shading after <code>computeVertexNormals()</code>, on the right is the original shading.</p>
  
  <p>How can I update the shading after the geometry changes?</p>