Cesium飞线

在学习Cesium过程中，发现Cesium的Material可以自定义自己所需的材质，看到网上其他资源有实现城市飞线的效果，感觉挺酷炫，于是经过一凡探索，实现了一下效果

调用实现方式：

  addFlyintLineByPrimitive(positions) {
                    // primitive方式添加
                    const primitive = new Cesium.Primitive({
                        geometryInstances: new Cesium.GeometryInstance({
                            geometry: new Cesium.PolylineGeometry({
                                positions: positions,
                                width: 1.0,
                                vertexFormat: Cesium.PolylineMaterialAppearance.VERTEX_FORMAT
                            })
                        }),
                        appearance: new Cesium.PolylineMaterialAppearance({
                            material: Cesium.Material.fromType(Cesium.Material.PolylineFlowType, {
                                speed: 10 * Math.random(),
                                color: Cesium.Color.CYAN,
                                percent: 0.1,
                                gradient: 0.01
                            }),
                        })
                    });
                    this.viewer.scene.primitives.add(primitive);
                },
                addFlyingLineByEntity(positions) {
                    //entity方式添加
                    this.viewer.entities.add({
                        polyline: {
                            positions: positions,
                            width: 2.0,
                            material: new Cesium.PolylineFlowMaterialProperty({
                                speed: 6 * Math.random(),
                                color: Cesium.Color.CYAN,
                                percent: 0.1,
                                gradient: 0.01
                            })
                        }
                    })
                },