www加载出来就跑
string url = UrlManager.GetWWWStreamingPath("/3DScene/" + scene + UrlManager.GetModelEnd());
WWW www = new WWW(url);
yield return www;
sceneAb = www.assetBundle;
www.Dispose();
UnityEngine.SceneManagement.Scene currScene = UnityEngine.SceneManagement.SceneManager.GetSceneByName(currSceneName);
UnityEngine.SceneManagement.SceneManager.SetActiveScene(currScene);