[]为什么动态设置聚光灯朝向无效呢

var tar = new Laya.Vector3();
var dir = new Laya.Vector3();
var src = model.transform.position;

spotLight.transform.position = camera.transform.position;
Laya.Vector3.subtract(src, camera.transform.position,tar);
Laya.Vector3.normalize(tar, dir);
spotLight.direction = dir;

目的是让聚光灯，始终朝向模型， 模型是在移动的， 但是没有光的效果？