cesium绘制区域边界

要在Cesium中绘制区域边界，可以使用以下步骤：

1. 创建一个Polygon实例，设置其位置和边界点坐标。

let polygon = viewer.entities.add({
  polygon: {
    hierarchy: Cesium.Cartesian3.fromDegreesArray([
      -115.0, 37.0,
      -115.0, 32.0,
      -107.0, 33.0,
      -102.0, 31.0,
      -102.0, 35.0
    ]),
    material: Cesium.Color.RED.withAlpha(0.5),
    outline: true,
    outlineWidth: 2,
    outlineColor: Cesium.Color.BLACK
  }
});

2. 将Polygon实例添加到场景中。

viewer.entities.add(polygon);

3. 设置Polygon实例的材质和边框属性。

polygon.polygon.material = Cesium.Color.RED.withAlpha(0.5);
polygon.polygon.outline = true;
polygon.polygon.outlineWidth = 2;
polygon.polygon.outlineColor = Cesium.Color.BLACK;

4. 通过设置Polygon实例的高度来使其浮在地球表面上。

polygon.polygon.height = 0;

完整的示例代码如下：

let viewer = new Cesium.Viewer("cesiumContainer");

let polygon = viewer.entities.add({
  polygon: {
    hierarchy: Cesium.Cartesian3.fromDegreesArray([
      -115.0, 37.0,
      -115.0, 32.0,
      -107.0, 33.0,
      -102.0, 31.0,
      -102.0, 35.0
    ]),
    material: Cesium.Color.RED.withAlpha(0.5),
    outline: true,
    outlineWidth: 2,
    outlineColor: Cesium.Color.BLACK,
    height: 0
  }
});

viewer.entities.add(polygon);