创建一个城市线条效果，加载FBX城市模型，使用EdgesGeometry提取建筑边缘线，创造赛博朋克风格的城市线框效果。

class City {
    constructor() {
        this.fbxLoader = new FBXLoader();
        this.group = new THREE.Group();
        this.clock = new THREE.Clock()
        this.surroundLineMaterial = null;
        this.time = { value: 0 };
        this.startTime = { value: 0 };
        this.startLength = { value: 2 }
        this.isStart = false;

        this.fbxLoader.load(FILE_HOST + 'models/fbx/shanghai.FBX', (group) => {
            this.group.add(group);
            group.traverse((child) => {
                // 设置城市建筑材质
                if (child.name == 'CITY_UNTRIANGULATED') {
                    const materials = Array.isArray(child.material) ? child.material : [child.material]
                    materials.forEach((material) => {
                        material.transparent = true;
                        material.color.setStyle("#9370DB");
                    })
                }

                // 设置城市地面材质
                if (child.name == 'LANDMASS') {
                    const materials = Array.isArray(child.material) ? child.material : [child.material]
                    materials.forEach((material) => {
                        material.transparent = true;
                        material.color.setStyle("#040912");
                    })
                }
            })

            this.init();
        });
    }
}

surroundLine() {
    let cityBuildings
    this.group.traverse(child => {
        if (child.name !== 'CITY_UNTRIANGULATED') return
        cityBuildings = child
    })

    const geometry = new THREE.EdgesGeometry(cityBuildings.geometry);
    const surroundLineMaterial = new THREE.ShaderMaterial({
        transparent: true,
        uniforms: {
            uColor: {
                value: new THREE.Color('#FFF')
            }
        },
        vertexShader: `
            void main() {
                gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
            }
        `,
        fragmentShader: ` 
            uniform vec3 uColor;
            void main() {
                gl_FragColor = vec4(uColor, 1);
            }
        `
    });

    const line = new THREE.LineSegments(geometry, surroundLineMaterial);
    line.name = 'surroundLine';
    line.applyMatrix4(cityBuildings.matrix.clone())
    cityBuildings.parent.add(line)
}