1. At first i get the terrain tile use `ctb-tile --output-dir ./terrain-tiles dem.tif`  2. The I add the data in tomcat webapp root dir, which as `apache-tomcat-10.0.2\webapps\ROOT\output-dir` 3. I add the terrain use ``` viewer.terrainProvider = new Cesium.CesiumTerrainProvider({ url : `http://localhost:8081/output-dir`, }); ``` 4. The world is black and can not see anything  5. The http request have only one for 0/1/0.terrain 