获取某地模型并用Cesium加载(一)

    var tileset = new Cesium.Cesium3DTileset({        url: "../../../static/3DModel/sicauOSM/tileset.json",      });      viewer.scene.primitives.add(tileset);     console.log(tileset);

    //3dtile加载完成后执行     tileset.readyPromise.then(function(tileset) {          //高度偏差，向上是正数，向下是负数     var heightOffset = 500.0;      //计算tileset的绑定范围     var boundingSphere = tileset.boundingSphere;      //计算中心点位置     /**      * fromCartesian 方法是用经纬度和高度定义一个位置      * A position defined by longitude, latitude, and height.      */     var cartographic = Cesium.Cartographic.fromCartesian(boundingSphere.center);      //计算中心点位置的地表坐标     /**      * Cartesian3 是一个3D点      * fromRadians 方法 Returns a Cartesian3 position from longitude and latitude values given in radians（弧度）.      * @param longitude      * @param latitude      * @param height      * 因为建筑模型没他所在高度信息，所以填0      */     var surface = Cesium.Cartesian3.fromRadians(cartographic.longitude, cartographic.latitude, 0.0);      //偏移后的坐标，也就是中心点本应在的高度（海拔）         var offset = Cesium.Cartesian3.fromRadians(cartographic.longitude, cartographic.latitude, heightOffset);      /**      * subtract 方法 Computes the componentwise difference of two Cartesians.      * 计算两个笛卡尔坐标的成分差异      * @param 就是两个要计算的坐标      * @param 第三个参数是要保存的结果      */     var translation = Cesium.Cartesian3.subtract(offset, surface, new Cesium.Cartesian3());      console.log(`translation长这样:     ${translation}`);     // (-102.97917011496611, 417.3715669941157, 255.33559404686093)      //tileset.modelMatrix转换     /**      * Creates a Matrix4 instance from a Cartesian3 representing the translation.      * @param {Cartesian3} translation - The upper right portion of the matrix representing the translation.      * @param {    Matrix4} result - The object in which the result will be stored, if undefined a new instance will be created.      * Cesium中使用Matrix4作为处理线性变换和位移变换的仿射矩阵      * 三维空间的转换矩阵通常是3x3的就可以      * 但是为了同时满足位移的需要增加了一个维度使用4x4的矩阵      */     console.log(`变化前的tileset.modelMatrix为:     ${tileset.modelMatrix}`);     // (1, 0, 0, 0)     // (0, 1, 0, 0)     // (0, 0, 1, 0)     // (0, 0, 0, 1)          tileset.modelMatrix = Cesium.Matrix4.fromTranslation(translation);     console.log(`变化后的tileset.modelMatrix为:     ${tileset.modelMatrix}`);     // (1, 0, 0, -102.97917011496611)     // (0, 1, 0, 417.3715669941157)     // (0, 0, 1, 255.33559404686093)     // (0, 0, 0, 1)      /**      * 定位到3dtiles的位置,也就是让摄像头对准这个区域      * viewBoundingSphere 方法      * Sets the camera so that the current view contains the provided bounding sphere.      * @param boundingSphere - The bounding sphere to view, in world coordinates.      * @param offset  - The offset from the target in the local east-north-up reference frame centered at the target.      */     viewer.camera.viewBoundingSphere(tileset.boundingSphere, new Cesium.HeadingPitchRange(0, -20, 0));      });