cesium点击获取entity的属性

在多数应用场景中，我们不仅需要绘制出空间对象还需要用鼠标拾取对象，cesium为我们提供了scene.pick接口，如下代码实现坐标左键单击实现对象的拾取：

 viewer.entities.add({

            id:'id',

            position: Cesium.Cartesian3.fromDegrees(103.0, 40.0),

            name: 'Red ellipse on surface with outline',

            ellipse: {

                semiMinorAxis: 250000.0,

                semiMajorAxis: 400000.0,

                height: 200000.0,