Cesium Vue（五）— 绘制多边形

1. 使用entity创建矩形

      var rectangle = viewer.entities.add({
    rectangle: {
      coordinates: Cesium.Rectangle.fromDegrees(
        // 西边的经度
        90,
        // 南边维度
        20,
        // 东边经度
        110,
        // 北边维度
        30
      ),
      material: Cesium.Color.GREEN.withAlpha(0.8),
    },

2. 使用primivite创建矩形

   // primivite创建矩形
  // 01-创建几何体
  let rectGeometry = new Cesium.RectangleGeometry({
    rectangle: Cesium.Rectangle.fromDegrees(
      // 西边的经度
      115,
      // 南边维度
      20,
      // 东边经度
      135,
      // 北边维度
      30
    ),
    // 距离表面高度
    height: 0,
    vertexFormat: Cesium.PerInstanceColorAppearance.VERTEX_FORMAT,
  });

  // 02-创建几何体实例
  let instance = new Cesium.GeometryInstance({
    geometry: rectGeometry,
    attributes: {
      color: Cesium.ColorGeometryInstanceAttribute.fromColor(
        Cesium.Color.RED.withAlpha(0.5)
      ),
    },
  });

  // 03-设置外观
  let appearance = new Cesium.PerInstanceColorAppearance({
    flat: true,
  });
  // 04-图元
  let primitive = new Cesium.Primitive({
    geometryInstances: instance,
    appearance: appearance,
  });
  // 05-添加到viewer
  viewer.scene.primitives.add(primitive);

  viewer.camera.setView(viewer.entities);

3. 创建多个实体在同一个primitive

 // 04-图元
  let primitive = new Cesium.Primitive({
    geometryInstances: [instance, instance2],// 在数组geometryInstances 中添加多个实体
    appearance: appearance,
  });

4. 修改primitive颜色

  // 动态修改图元颜色
  setInterval(() => {
    let attributes = primitive.getGeometryInstanceAttributes("blueRect");
    attributes.color = Cesium.ColorGeometryInstanceAttribute.toValue(
      // Cesium.Color.YELLOW.withAlpha(0.5)
      Cesium.Color.fromRandom({
        alpha: 0.5,
      })
    );
  }, 2000);
  });

5. primitive和entity物体交互

// 拾取
  var handler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
  handler.setInputAction(function (movement) {
    // console.log(movement);
    // scene.pick选中物体
    var pickedObject = viewer.scene.pick(movement.position);
    console.log(pickedObject);
    if (Cesium.defined(pickedObject) && typeof pickedObject.id == "string") {
      // console.log(pickedObject.id);
      let attributes = primitive.getGeometryInstanceAttributes(pickedObject.id);
      attributes.color = Cesium.ColorGeometryInstanceAttribute.toValue(
        Cesium.Color.YELLOW.withAlpha(0.5)
      );
    }
  }, Cesium.ScreenSpaceEventType.LEFT_CLICK);