function generateCurve(startPoint, endPoint){

        let addPointCartesian = new Cesium.Cartesian3();

        Cesium.Cartesian3.add(startPoint, endPoint, addPointCartesian);

        let midPointCartesian = new Cesium.Cartesian3();

        Cesium.Cartesian3.divideByScalar(addPointCartesian, 2, midPointCartesian);

        let midPointCartographic = Cesium.Cartographic.fromCartesian(midPointCartesian);

                    //除以的这个数越小 开始的位置聚集的位置就越陡，越大 开始的位置线就越平缓，

        midPointCartographic.height = Cesium.Cartesian3.distance(startPoint, endPoint) / 10;

        let midPoint = new Cesium.Cartesian3();

        Cesium.Ellipsoid.WGS84.cartographicToCartesian(midPointCartographic, midPoint);

        let spline = new Cesium.CatmullRomSpline({

            times: [0.0, 0.5, 1.0],

            points: [startPoint, midPoint, endPoint]

        });

        let curvePointsArr = [];

        for(let i = 0, len = 300; i < len; i++){

            curvePointsArr.push(spline.evaluate(i / len));

        }

        return curvePointsArr;

    }

let curLinePointsArr = generateCurve(startPt, endPt);

//构造实体动线的配置

viewer.entities.add({

    description: "飞天动态轨迹线",

    show: true,

    polyline: {

        width: 3,

        positions: curLinePointsArr,

        material: new Cesium.PolylineTrailMaterialProperty({ // 尾迹线材质

            //指定线型的填充颜色，替换为白色。

            color: new Cesium.Color.fromCssColorString("rgba(70,130,180, 1.0)"),

            //指定轮廓线的颜色，可选的黑色。

            outlineColor: new Cesium.Color(70 / 255, 130 / 255, 180 / 255, 0.3),

            //设置尾迹线的长度在整条线中占的比例，替换数值0.3

            trailLength: 0.8,

            //数值属性，设置尾迹线从起点到终点的运行周期，单位是秒，每次转换1000.0。

            period: 3

        }),

    }

});