在没有任何给定坐标的情况下，threejs如何将网格放置到场景中？

// 创建场景
var scene = new THREE.Scene();

// 创建相机
var camera = new THREE.PerspectiveCamera(75, window.innerWidth / window.innerHeight, 0.1, 1000);
camera.position.z = 5;

// 创建渲染器
var renderer = new THREE.WebGLRenderer();
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);

// 创建立方体网格
var geometry = new THREE.BoxGeometry();
var material = new THREE.MeshBasicMaterial({ color: 0x00ff00 });
var cube = new THREE.Mesh(geometry, material);

// 将立方体网格添加到场景中
scene.add(cube);

// 渲染场景
function animate() {
    requestAnimationFrame(animate);
    cube.rotation.x += 0.01;
    cube.rotation.y += 0.01;
    renderer.render(scene, camera);
}
animate();