code: function updateVirtualLight( light, cascade ) {
  
  		var virtualLight = light.shadowCascadeArray[ cascade ];
  
  		virtualLight.position.copy( light.position );
  		virtualLight.target.position.copy( light.target.position );
  		virtualLight.lookAt( virtualLight.target );
  
  		virtualLight.shadowCameraVisible = light.shadowCameraVisible;
  		virtualLight.shadowDarkness = light.shadowDarkness;
  
  		virtualLight.shadowBias = light.shadowCascadeBias[ cascade ];
  
  		var nearZ = light.shadowCascadeNearZ[ cascade ];
  		var farZ = light.shadowCascadeFarZ[ cascade ];
  
  		var pointsFrustum = virtualLight.pointsFrustum;
  
  		pointsFrustum[ 0 ].z = nearZ;
  		pointsFrustum[ 1 ].z = nearZ;
  		pointsFrustum[ 2 ].z = nearZ;
  		pointsFrustum[ 3 ].z = nearZ;
  
  		pointsFrustum[ 4 ].z = farZ;
  		pointsFrustum[ 5 ].z = farZ;
  		pointsFrustum[ 6 ].z = farZ;
  		pointsFrustum[ 7 ].z = farZ;
  
  	}
docs: Synchronize virtual light with the original light