cesium画流动箭头线

要在cesium中绘制流动箭头线，可以使用Cesium的PolylineGlowMaterial材质和Primitive类型。以下是一个示例代码：

// 创建流动箭头线的起点和终点
var start = Cesium.Cartesian3.fromDegrees(-75.0, 40.0);
var end = Cesium.Cartesian3.fromDegrees(-125.0, 35.0);

// 计算两点之间的距离
var distance = Cesium.Cartesian3.distance(start, end);

// 创建流动箭头线的坐标数组
var positions = [start, end];

// 创建流动箭头线的颜色
var color = new Cesium.Color(1.0, 0.0, 0.0, 1.0);

// 计算流动箭头线的方向和长度
var direction = Cesium.Cartesian3.normalize(Cesium.Cartesian3.subtract(end, start, new Cesium.Cartesian3()), new Cesium.Cartesian3());
var length = distance / 10.0;

// 创建流动箭头线的箭头部分的坐标
var arrowEnd = Cesium.Cartesian3.add(start, Cesium.Cartesian3.multiplyByScalar(direction, length, new Cesium.Cartesian3()), new Cesium.Cartesian3());
var arrowLeft = Cesium.Cartesian3.add(arrowEnd, Cesium.Cartesian3.multiplyByScalar(Cesium.Cartesian3.normalize(Cesium.Cartesian3.cross(direction, Cesium.Cartesian3.UNIT_Z, new Cesium.Cartesian3()), new Cesium.Cartesian3()), length / 3.0, new Cesium.Cartesian3()), new Cesium.Cartesian3());
var arrowRight = Cesium.Cartesian3.add(arrowEnd, Cesium.Cartesian3.multiplyByScalar(Cesium.Cartesian3.normalize(Cesium.Cartesian3.cross(Cesium.Cartesian3.negate(direction), Cesium.Cartesian3.UNIT_Z, new Cesium.Cartesian3()), new Cesium.Cartesian3()), length / 3.0, new Cesium.Cartesian3()), new Cesium.Cartesian3());

// 创建流动箭头线的坐标数组
var arrowPositions = [arrowEnd, arrowLeft, arrowRight, arrowEnd];

// 创建流动箭头线的几何体
var geometry = new Cesium.PolylineGeometry({
    positions: positions,
    width: 10.0,
    vertexFormat: Cesium.VertexFormat.POSITION_AND_NORMAL
});

// 创建流动箭头线的材质
var material = new Cesium.PolylineGlowMaterialProperty({
    glowPower: 0.2,
    color: color
});

// 创建流动箭头线的Primitive
var primitive = new Cesium.Primitive({
    geometryInstances: new Cesium.GeometryInstance({
        geometry: geometry,
        attributes: {
            color: Cesium.ColorGeometryInstanceAttribute.fromColor(color)
        },
        id: 'line'
    }),
    appearance: new Cesium.PolylineMaterialAppearance({
        material: material
    }),
    show: true
});

// 将流动箭头线添加到场景中
viewer.scene.primitives.add(primitive);

这段代码创建了一个从（-75.0，40.0）到（-125.0，35.0）的流动箭头线，并将其添加到Cesium场景中。箭头线的颜色为红色，宽度为10.0。箭头部分的长度是线段总长度的1/10，箭头部分的左右两侧各为长度的1/3。箭头线的材质为PolylineGlowMaterial，使其在场景中呈现出流动的效果。