this.scene = Laya.stage.addChild(new Laya.Scene3D()) as Laya.Scene3D; 
        this.camera = new Laya.Camera();
        this.camera.transform.translate(new Laya.Vector3(0, 2, 5));
        this.camera.transform.rotate(new Laya.Vector3(-30, 0, 0), true, false); 
        this.scene.addChild(this.camera);
        Laya.loader.create("res/scene_Effect/Conventional/Effect_zhujue_attack.lh", Laya.Handler.create(this, () => { 
            let item = Laya.loader.getRes("res/scene_Effect/Conventional/Effect_zhujue_attack.lh");
            let tarItem = Laya.Sprite3D.instantiate(item);
            this.scene.addChild(tarItem);
            tarItem.transform.position = new Laya.Vector3(0, 0, 0);
            item.destroy();
            item = null;
            tarItem.destroy();
            tarItem = null;
            this.camera.removeSelf();
            this.camera.destroy(true);
            this.camera = null; 
            this.scene.destroy();
            Laya.Scene.gc();
        }));

以上为测试代码，若在相机添加到场景之前load资源，可正常销毁3d场景及其内存占用

附件：
TestShaderInstance.zip

TestShaderInstance.zip