本节演示添加billboard小旗子，使用第四节click的例子，通过鼠标点击地图添加billboard添加小旗子。

1、修改鼠标点击事件mouseUp，在函数中创建BillboardCollection对象并添加到地图中。鼠标点击时获取鼠标位置，转换成经纬度然后添加billboard。

static void mouseUp(void *handler, Cesium::ScreenEvent *event) {
    Handler *aggregator = (Handler *) handler;

    if (aggregator->billboards == NULL) {
        // 创建BillboardCollection
        aggregator->billboards = new Cesium::BillboardCollection(NULL);
        aggregator->viewer->_scene->primitives()->add(aggregator->billboards);
    }
    glm::dvec2 position = event->position;//鼠标屏幕位置
    glm::dvec3 coor, carthposition;
    //转换成经纬度，与cesium基本一致
    aggregator->viewer->_scene->_camera->pickEllipsoid(position,
                                                       aggregator->viewer->_scene->_globe->_ellipsoid,
                                                       &coor);
    aggregator->viewer->_scene->_globe->_ellipsoid->cartesianToCartographic(coor, &carthposition);
    double longitude = Cesium::CesiumMath::toDegrees(carthposition.x);
    double latitude = Cesium::CesiumMath::toDegrees(carthposition.y);
    //添加billboard
    glm::dvec3 initialPosition2 = Cesium::Cartesian3::fromDegrees(longitude, latitude);
    aggregator->billboards->add(initialPosition2, "../data/home.png");

}

2、运行地图，点击地图即可添加一个billboard。

完整代码

/**
 * Created by IBM on 2021/3/3.
 */
#include <iostream>
#include <Widgets/Viewer/Viewer.h>
#include <Scene/BillboardCollection.h>


class Handler {
public:
    Cesium::Viewer *viewer;
    Cesium::BillboardCollection *billboards = NULL;

    /**
     * 鼠标抬起事件
     * @param type
     * @param position
     */
    static void mouseUp(void *handler, Cesium::ScreenEvent *event) {
        Handler *aggregator = (Handler *) handler;

        if (aggregator->billboards == NULL) {
            // 创建BillboardCollection
            aggregator->billboards = new Cesium::BillboardCollection(NULL);
            aggregator->viewer->_scene->primitives()->add(aggregator->billboards);
        }
        glm::dvec2 position = event->position;//鼠标屏幕位置
        glm::dvec3 coor, carthposition;
        //转换成经纬度，与cesium基本一致
        aggregator->viewer->_scene->_camera->pickEllipsoid(position,
                                                           aggregator->viewer->_scene->_globe->_ellipsoid,
                                                           &coor);
        aggregator->viewer->_scene->_globe->_ellipsoid->cartesianToCartographic(coor, &carthposition);
        double longitude = Cesium::CesiumMath::toDegrees(carthposition.x);
        double latitude = Cesium::CesiumMath::toDegrees(carthposition.y);
        //添加billboard
        glm::dvec3 initialPosition2 = Cesium::Cartesian3::fromDegrees(longitude, latitude);
        aggregator->billboards->add(initialPosition2, "../data/home.png");

    }
};

int main(int argc, char *argv[]) {
    Handler *handler = new Handler();
    Cesium::Viewer viewer = Cesium::Viewer(500, 300);
    handler->viewer = &viewer;
    std::string url = "https://dev.virtualearth.net";
    std::string key = "AmXdbd8UeUJtaRSn7yVwyXgQlBBUqliLbHpgn2c76DfuHwAXfRrgS5qwfHU6Rhm8";
    Cesium::BingMapsImageryProvider *imageryProvider1 = new Cesium::BingMapsImageryProvider(url, key);
    viewer.imageryLayers()->addImageryProvider(imageryProvider1);
    //创建事件
    Cesium::ScreenSpaceEventHandler *_eventHandler = new Cesium::ScreenSpaceEventHandler(handler);
    _eventHandler->setInputAction(&Handler::mouseUp, Cesium::ScreenSpaceEventType::LEFT_CLICK);//设置鼠标点击事件
    viewer.startAnimating(true);//启动opengl循环
    system("pause");
    return 0;
}

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