自定义绘制多边形

刚刚分享了地形开挖，觉得可能大部分业务是自定义多边形，然后开挖，基于此，分享自定义绘制多边形函数，引入即可使用

// 构造唯一id
import { v4 as uuidv4 } from 'uuid';
// 坐标转化
const getLonLatFromCartesian = (cartesian3) => {
    const { longitude, latitude, height } = Cesium.Cartographic.fromCartesian(cartesian3);
    return {
        lng: +Cesium.Math.toDegrees(longitude),
        lat: +Cesium.Math.toDegrees(latitude),
        height: +height
    }
};
// 创建点
const createPoint = (viewer, Cartesian, options) => {
    const { lng, lat, height } = getLonLatFromCartesian(Cartesian)
    return viewer.entities.add({
        position: new Cesium.Cartesian3.fromDegrees(lng, lat, height),
        point: {
            pixelSize: options.pixelSize, 
            color: options.pointColor   
        }
    })
};
// 绘制多边形
const DrawPolygon = (viewer, options = {}, callback) => {
    if (!viewer) throw new Error("no viewer object!");
    options = {
      id: uuidv4(),
      pointColor: Cesium.Color.fromCssColorString('#FFC107'),
      pixelSize: 8,
      outlineWidth: 5,
      outlineColor: new Cesium.Color(0, 64 / 255, 133 / 255, 0.8),
      color: Cesium.Color.fromCssColorString('rgba(0, 123, 255, 0.4)'),
      ...options
    };
    if (viewer.entities.getById(options.id)) {
      throw new Error("the id is an unique value");
    }
    const handler = new Cesium.ScreenSpaceEventHandler(viewer.canvas);
    let activeShapePoints = [];
    let polygon = undefined;
    let floatingPoint = undefined;
    // 鼠标左击事件
    handler.setInputAction((event) => {
      let ray = viewer.camera.getPickRay(event.position);
      let earthPosition = viewer.scene.globe.pick(ray, viewer.scene);
      // 鼠标开始点击多边形的第一个点
      if (activeShapePoints.length === 0) {
        floatingPoint = createPoint(viewer, earthPosition, options);
        // 将第一个左击的点添加到多边形顶点集合中
        activeShapePoints.push(earthPosition);
        // 多边形的坐标采用回调的形式
        // 多边形边界顶点
        let polylinePoints = new Cesium.CallbackProperty(() => {
          let vertexPoints = activeShapePoints.concat([activeShapePoints[0]]);
          return vertexPoints;
        }, false);
        // 多边形顶点
        let dynamicPositions = new Cesium.CallbackProperty(() => {
          return new Cesium.PolygonHierarchy(activeShapePoints);
        }, false);
        // 添加一个多边形
        polygon = viewer.entities.add({
          name: "customPolygon",
          id: options.id,
          polyline: {
            positions: polylinePoints,
            width: options.outlineWidth,
            material: options.outlineColor,
            clampToGround: true,
          },
          polygon: {
            hierarchy: dynamicPositions,
            material: options.color,
            heightReference: Cesium.HeightReference.NONE,
          },
        });
      }
      // 将鼠标点击的点添加到多边形顶点集合中
      activeShapePoints.push(earthPosition);
      // 记录多边形边界的点
      polygon.outLinePoint = (polygon.outLinePoint ?? []).concat(createPoint(viewer, earthPosition, options));
    }, Cesium.ScreenSpaceEventType.LEFT_CLICK);
    // 鼠标移动事件
    handler.setInputAction((movement) => {
      // 获取鼠标所在的位置
      const ray = viewer.camera.getPickRay(movement.endPosition);
      const newPosition = viewer.scene.globe.pick(ray, viewer.scene);
      // 已经定义了polygon
      if (Cesium.defined(polygon)) {
        floatingPoint.position.setValue(newPosition);
        // 删除多边形顶点中最新的一个点
        activeShapePoints.pop();
        // 将最新获取到的点添加到多边形顶点集合中
        activeShapePoints.push(newPosition);
      }
      if (activeShapePoints.length === 3) {
        polygon.polygon.heightReference = Cesium.HeightReference.CLAMP_TO_GROUND;
      }
    }, Cesium.ScreenSpaceEventType.MOUSE_MOVE);
    handler.setInputAction(() => {
      // 删除最后一个点（重复添加的点）
      activeShapePoints.pop();
      polygon.pottingPoint = activeShapePoints;
      viewer.entities.remove(floatingPoint);
      floatingPoint = undefined;
      // 销毁右击事件
      handler.destroy();
      if (typeof callback === "function") callback(polygon);
    }, Cesium.ScreenSpaceEventType.RIGHT_DOWN);
  };
  export default DrawPolygon;

使用方法

DrawPolygon(this.viewer, {}, (polygon) => {
    console.log(polygon)
})

效果图