[]laya默认模型的阴影没有渲染

//初始化微信小游戏
Laya.MiniAdpter.init();
//初始化引擎
Laya3D.init(0, 0, true);

//适配模式
Laya.stage.scaleMode = Laya.Stage.SCALE_FULL;
Laya.stage.screenMode = Laya.Stage.SCREEN_NONE;

//开启统计信息
Laya.Stat.show();

//添加3D场景
var scene = Laya.stage.addChild(new Laya.Scene());



//添加照相机
var camera = (scene.addChild(new Laya.Camera(0, 0.1, 1000)));
camera.transform.translate(new Laya.Vector3(0, 5, 0));
camera.transform.rotate(new Laya.Vector3(-30, 0, 0), true, false);
camera.clearColor = null;

//添加方向光
var directionLight = scene.addChild(new Laya.DirectionLight());
directionLight.color = new Laya.Vector3(0.8, 0.8, 0.8);
directionLight.direction = new Laya.Vector3(-1, -1, 2);

//灯光开启阴影
directionLight.shadow = true;
//可见阴影距离
directionLight.shadowDistance = 300;
//生成阴影贴图尺寸
directionLight.shadowResolution = 2048;
//生成阴影贴图数量
directionLight.shadowPSSMCount = 1;
//模糊等级,越大越高,更耗性能
directionLight.shadowPCFType = 1;



//添加自定义模型
//
//创建模型显示对象
var sphere3D=new Laya.MeshSprite3D(new Laya.SphereMesh(1, 32, 32));
sphere3D.transform.translate(new Laya.Vector3(0,1,-5));
var box = scene.addChild(sphere3D);
box.transform.rotate(new Laya.Vector3(0, 45, 0), false, false);
// var material = new Laya.StandardMaterial();

// material.diffuseTexture = Laya.Texture2D.load("res/qiu/6.jpg");
// box.meshRender.material = material;

box.meshRender.receiveShadow=true;
box.meshRender.castShadow=true;


var box2 = scene.addChild(new Laya.MeshSprite3D(new Laya.BoxMesh(10, 10, 1)));
box2.transform.translate(new Laya.Vector3(0,.1,-5));

// var material2 = new Laya.StandardMaterial();
//
// material2.diffuseTexture = Laya.Texture2D.load("res/qiu/5.jpg");

// box2.meshRender.material=material2;

box2.meshRender.receiveShadow=true;
box2.meshRender.castShadow=true;


我就是这样简单的3D场景， 修改好多次就是没有阴影。。 麻烦技术大大帮忙看看。