cesium用primitive画线

以下是使用Cesium的Primitive绘制线的示例代码：

// 创建Cesium Viewer对象
var viewer = new Cesium.Viewer('cesiumContainer');

// 创建一个PrimitiveCollection对象
var primitives = new Cesium.PrimitiveCollection();
viewer.scene.primitives.add(primitives);

// 定义线的顶点坐标
var positions = Cesium.Cartesian3.fromDegreesArray([
    -75, 35,
    -125, 35,
    -125, 65,
    -75, 65,
    -75, 35
]);

// 创建一个Geometry对象
var geometry = new Cesium.PolylineGeometry({
    positions: positions,
    width: 5.0,
    vertexFormat: Cesium.VertexFormat.ALL
});

// 创建一个Appearance对象
var appearance = new Cesium.PolylineMaterialAppearance({
    material: Cesium.Material.fromType('Color', {
        color: Cesium.Color.RED
    })
});

// 创建一个Primitive对象
var primitive = new Cesium.Primitive({
    geometryInstances: new Cesium.GeometryInstance({
        geometry: geometry
    }),
    appearance: appearance,
    asynchronous: false
});

// 将Primitive对象添加到PrimitiveCollection中
primitives.add(primitive);