code: function setupShadows ( lights ) {
  
  		var lightShadowsLength = 0;
  
  		for ( var i = 0, l = lights.length; i < l; i ++ ) {
  
  			var light = lights[ i ];
  
  			if ( light.castShadow ) {
  
  				_lights.shadows[ lightShadowsLength ++ ] = light;
  
  			}
  
  		}
  
  		_lights.shadows.length = lightShadowsLength;
  
  	}
docs: Lighting