在SuperMap iClient3D 11i(2022) for Cesium中使用DynamicLayer3D图层，实现将S3M模型绕某倾斜摄影三维模型服务循环飞行。

实现将S3M模型绕某倾斜摄影三维模型服务循环飞行的过程可以分为以下几步：

1. 创建Cesium Viewer对象和SuperMap iClient3D的场景。

   var viewer = new Cesium.Viewer("cesiumContainer");
   var scene = viewer.scene;
   var iClient3D = new SuperMap.Web.iClient3DLayer(scene);

2. 创建DynamicLayer3D图层对象，设置图层参数。

   var dynamicLayer3D = new SuperMap.Web.iClient3D.DynamicLayer3D({
       url: "http://localhost:8090/iserver/services/3D-Model/rest/realspace",  // 倾斜摄影三维模型服务地址
       name: "s3m_layer",   // 图层名称
       datasources: ["gugong"],   // 数据源名称
       visible: true  // 图层可见性
   });

这里需要注意的是，需要在倾斜摄影三维模型服务中发布S3M模型，并将其归属到指定的数据源中。

3. 将DynamicLayer3D图层添加到SuperMap iClient3D的场景中。

   iClient3D.addLayer(dynamicLayer3D);

4. 获取倾斜摄影三维模型的高度信息。

   var terrainProvider = new Cesium.CesiumTerrainProvider({
       url: "http://localhost:8090/iserver/services/3D-Model/rest/realspace/datas/gugong/config",
   });
   var ellipsoid = scene.globe.ellipsoid;
   var promise = Cesium.sampleTerrainMostDetailed(terrainProvider, [camera.positionCartographic]);
   Cesium.when(promise, function(updatedPositions) {
       var height = updatedPositions[0].height;
       camera.position = ellipsoid.cartographicToCartesian(
           new Cesium.Cartographic.fromDegrees(116.403964, 39.915119, height + 7000)
       );
       camera.up = new Cesium.Cartesian3(0, 0, 1);
       camera.lookAt(new Cesium.Cartesian3(116.403964, 39.915119, height + 100), new Cesium.Cartesian3(0, 0, height + 7000));
   });

这里需要使用Cesium的sampleTerrainMostDetailed方法来获取倾斜摄影三维模型的高度信息，并将相机位置设置在模型上方。

5. 创建动画函数，实现循环飞行效果。

   var heading = 0;
   function flyLoop() {
       var pitch = Cesium.Math.toRadians(30);
       var roll = Cesium.Math.toRadians(0);

       heading += Cesium.Math.toRadians(1);
       if (heading > Cesium.Math.TWO_PI) {
           heading -= Cesium.Math.TWO_PI;
       }

       var position = Cesium.Cartesian3.fromDegrees(
           116.403964 + Math.cos(heading) * 0.01,
           39.915119 + Math.sin(heading) * 0.01,
           camera.positionCartographic.height
       );
       camera.setView({
           destination: position,
           orientation: {
               heading: heading,
               pitch: pitch,
               roll: roll
           }
       });
   }

这里的循环飞行效果是通过不断修改相机位置和方向实现的。

6. 调用动画函数，启动循环飞行效果。

   setInterval(flyLoop, 50);

这里使用setInterval函数每隔50毫秒调用一次动画函数，实现循环飞行效果。

完整代码如下所示：

var viewer = new Cesium.Viewer("cesiumContainer");
var scene = viewer.scene;
var iClient3D = new SuperMap.Web.iClient3DLayer(scene);

var dynamicLayer3D = new SuperMap.Web.iClient3D.DynamicLayer3D({
    url: "http://localhost:8090/iserver/services/3D-Model/rest/realspace",
    name: "s3m_layer",
    datasources: ["gugong"],
    visible: true
});
iClient3D.addLayer(dynamicLayer3D);

var terrainProvider = new Cesium.CesiumTerrainProvider({
    url: "http://localhost:8090/iserver/services/3D-Model/rest/realspace/datas/gugong/config",
});
var ellipsoid = scene.globe.ellipsoid;
var promise = Cesium.sampleTerrainMostDetailed(terrainProvider, [camera.positionCartographic]);
Cesium.when(promise, function(updatedPositions) {
    var height = updatedPositions[0].height;
    camera.position = ellipsoid.cartographicToCartesian(
        new Cesium.Cartographic.fromDegrees(116.403964, 39.915119, height + 7000)
    );
    camera.up = new Cesium.Cartesian3(0, 0, 1);
    camera.lookAt(new Cesium.Cartesian3(116.403964, 39.915119, height + 100), new Cesium.Cartesian3(0, 0, height + 7000));
});

var heading = 0;
function flyLoop() {
    var pitch = Cesium.Math.toRadians(30);
    var roll = Cesium.Math.toRadians(0);

    heading += Cesium.Math.toRadians(1);
    if (heading > Cesium.Math.TWO_PI) {
        heading -= Cesium.Math.TWO_PI;
    }

    var position = Cesium.Cartesian3.fromDegrees(
        116.403964 + Math.cos(heading) * 0.01,
        39.915119 + Math.sin(heading) * 0.01,
        camera.positionCartographic.height
    );
    camera.setView({
        destination: position,
        orientation: {
            heading: heading,
            pitch: pitch,
            roll: roll
        }
    });
}

setInterval(flyLoop, 50);