cesium 位置，旋转，高度 修改

调整模型高度

let offsetHeight=10;
var tileset = viewer.scene.primitives.add(new Cesium.Cesium3DTileset({
           url: '../test/tileset.json'
       }));
       viewer.scene.primitives.add(tileset);
       tileset.readyPromise.then(function(tileset) {
           var boundingSphere = tileset.boundingSphere;
           var cartographic = Cesium.Cartographic.fromCartesian(boundingSphere.center);
           var surface = Cesium.Cartesian3.fromRadians(cartographic.longitude, cartographic.latitude, 0.0);
           var offset = Cesium.Cartesian3.fromRadians(cartographic.longitude, cartographic.latitude, offsetHeight);
           var translation = Cesium.Cartesian3.subtract(offset, surface, new Cesium.Cartesian3());
           tileset.modelMatrix = Cesium.Matrix4.fromTranslation(translation);
​
           //viewer.zoomTo(tileset, new Cesium.HeadingPitchRange(0.5, -0.2, tileset.boundingSphere.radius * 1.0));
       });