Why do we need to copy the webgl camera?

[Joe Pea]

threex.htmlmixer/threex.htmlmixer.js

Lines 36 to 48 in 43fdd57

 ////////////////////////////////////////////////////////////////////////////////// 
 //		Handle Camera 
 ////////////////////////////////////////////////////////////////////////////////// 
  
 var cssCamera	= new THREE.PerspectiveCamera(camera.fov, camera.aspect, camera.near*cssFactor, camera.far*cssFactor); 
  
 updateFcts.push(function(){ 
 	cssCamera.quaternion.copy(camera.quaternion) 
  
 	cssCamera.position 
 		.copy(camera.position) 
 		.multiplyScalar(cssFactor) 
 }) 

?