Cesium基础知识三

// 添加多边形
viewer.entities.add({
    name: "Red polygon on surface",
    polygon: {
        hierarchy: Cesium.Cartesian3.fromDegreesArray([
            120.3506,30.338851,
            120.3536,30.338851,
            120.3536,30.340851,
            120.3506,30.340851,
            120.3506,30.338851,
        ]),
        material: Cesium.Color.RED,
    },
});

// 添加事件监听
_this.eventListener = _this.viewer.clock.onTick.addEventListener(function() {
    _this.render(_this.geometry);
});
// 取消事件监听
_this.eventListener();

// 添加标注
var polyPositions = polygon.hierarchy.getValue(Cesium.JulianDate.now()).positions;
var polyCenter = Cesium.BoundingSphere.fromPoints(polyPositions).center;//中心点
polyCenter = Cesium.Ellipsoid.WGS84.scaleToGeodeticSurface(polyCenter);
let cartographic = Cesium.Cartographic.fromCartesian(polyCenter, viewer.scene.globe.ellipsoid, new Cesium.Cartographic());
// 转换为经纬度
let lat = Cesium.Math.toDegrees(cartographic.latitude);
let lng = Cesium.Math.toDegrees(cartographic.longitude);
let height = cartographic.height;
entity.position=Cesium.Cartesian3.fromDegrees(lng, lat,height); // 设置标注的位置
entity.label= new Cesium.LabelGraphics({
    position: Cesium.Cartesian3.fromDegrees(lng, lat,height),
    text:entity.name,
    color : Cesium.Color.fromCssColorString('#fff'),
    font:'normal 32px MicroSoft YaHei',
    showBackground : false,
    scale : 0.5,
    verticalOrigin: Cesium.VerticalOrigin.BOTTOM,
    horizontalOrigin: Cesium.HorizontalOrigin.CENTER,
    heightReference: Cesium.HeightReference.CLAMP_TO_GROUND,
});