THREE.PerspectiveCamera( 50, window.innerWidth / window.innerHeight, 1, 20000 );

Why on earth did you use FOV of 50? Default on quake is 90, and in most games.

Also, 95% of the professional players play with fov in range 100 - 130. (I personally play with 130)

For the sake of the demo, i think this needs to be fixed to at least 90 deg. This is like trying to walk trough room looking trough a plastic pipe, you see whats in front of you, but you need way more information to move comfortably.