使用 Three.js 的 BufferGeometry 索引功能创建几何体，展示如何使用索引优化顶点数据。

const geometry = new THREE.BufferGeometry();
const vertices = new Float32Array([
    0, 0, 0, 50, 0, 0, 50, 0, 50,
    0, 0, 50,
]);

// 下面索引值对应顶点位置数据中的顶点坐标
// 第 0、1、2 这三个点构成一个三角形
// 第 0、3、2 这三个点构成一个三角形
const indexes = new Uint16Array([0, 1, 2, 0, 3, 2]);

geometry.index = new THREE.BufferAttribute(indexes, 1);
geometry.attributes.position = new THREE.BufferAttribute(vertices, 3);

const material2 = new THREE.PointsMaterial({
    color: 0xffff00,
    size: 10.0,
});
const points = new THREE.Points(geometry, material2);
scene.add(points);

const material1 = new THREE.LineBasicMaterial({
    color: 0xff0000,
});
const line = new THREE.Line(geometry, material1);
scene.add(line);

const material = new THREE.MeshBasicMaterial({
    color: 0x0000ff,
    side: THREE.DoubleSide,
});
const mesh = new THREE.Mesh(geometry, material);
scene.add(mesh);