为了计算BufferGeometry的交点，可以使用THREE.BufferGeometryUtils.computeIntersection()方法。需要传递原始的BufferGeometry对象和一个射线对象作为参数。该方法返回一个包含交点信息的对象。

示例代码：

// 创建一个BufferGeometry对象
var geometry = new THREE.BufferGeometry();

// 填充顶点和索引数据
var positions = new Float32Array([...]);
var indices = new Uint32Array([...]);

geometry.addAttribute('position', new THREE.BufferAttribute(positions, 3));
geometry.setIndex(new THREE.BufferAttribute(indices, 1));

// 创建一个射线对象
var raycaster = new THREE.Raycaster();
raycaster.set(new THREE.Vector3(0, 0, 0), new THREE.Vector3(0, 1, 0)); // 设置射线的起点和方向

// 计算交点
var intersection = THREE.BufferGeometryUtils.computeIntersection(geometry, raycaster);

// 打印交点信息
console.log('交点:', intersection.point, '法线:', intersection.face.normal);