docs: function GLTFMaterialsCommonExtension( json ) {
  
  		this.name = EXTENSIONS.KHR_MATERIALS_COMMON;
  
  		this.lights = {};
  
  		var lights = json.extensions && json.extensions[ EXTENSIONS.KHR_MATERIALS_COMMON ].lights;
  
  		for ( var lightId in lights ) {
  
  			var light = lights[ lightId ];
  			var lightNode;
  
  			var lightParams = light[ light.type ];
  			var color = new THREE.Color().fromArray( lightParams.color );
  
  			switch ( light.type ) {
  
  				case "directional":
  					lightNode = new THREE.DirectionalLight( color );
  					lightNode.position.set( 0, 0, 1 );
  					break;
  
  				case "point":
  					lightNode = new THREE.PointLight( color );
  					break;
  
  				case "spot":
  					lightNode = new THREE.SpotLight( color );
  					lightNode.position.set( 0, 0, 1 );
  					break;
  
  				case "ambient":
  					lightNode = new THREE.AmbientLight( color );
  					break;
  
  			}
  
  			if ( lightNode ) {
  
  				this.lights[ lightId ] = lightNode;
  
  			}
  
  		}
  
  	}