face culling</p>
      <p>In case you are inside the cube, by default Sandy's engine still doesn't draw the internal faces
   (because you should not be in there).</p> 
      <p>If you need to be only inside the cube, you can call this method to change which side is culled.<br/>
   The faces will be visible only from the interior of the cube.</p>
      <p>If you want to be both on the inside and the outside, you want to make the faces visible from on both sides.<br/>
   In that case you just have to set ena