cesium自定义地图瓦片wtms、cesium自定义图层

viewer.scene.imageryLayers.addImageryProvider(
          new Cesium.UrlTemplateImageryProvider({
            maximumLevel: 20,
            url: 'http://local.city.com/map_nanan_zxy/test/t4/{z}/{x}/{y}.jpg',//根据瓦片实际地址为准
            fileExtension: "jpg"
          })
);