[LayaAirIDE 2.0]3D场景中背景无法透明，版本2.7.1

export default class GameUI extends Laya.Scene {

    constructor() {

        super();



        Config.isAlpha = true;

       Laya.init(480, 900);

       Laya.stage.bgColor = null;



        //加载场景文件

        this.loadScene("test/TestScene.scene");



        //添加3D场景

        var scene = Laya.stage.addChild(new Laya.Scene3D());



        //添加照相机

        var camera = (scene.addChild(new Laya.Camera(0, 0.1, 100)));

        camera.transform.translate(new Laya.Vector3(0, 3, 3));

        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(0.6, 0.6, 0.6);

        directionLight.transform.worldMatrix.setForward(new Laya.Vector3(1, -1, 0));



        //添加自定义模型

        var box = scene.addChild(new Laya.MeshSprite3D(Laya.PrimitiveMesh.createBox(1, 1, 1)));

        box.transform.rotate(new Laya.Vector3(0, 45, 0), false, false);

        var material = new Laya.BlinnPhongMaterial();

		Laya.Texture2D.load("res/layabox.png", Laya.Handler.create(null, function(tex) {

				material.albedoTexture = tex;

		}));

        box.meshRenderer.material = material;

    }



}