レベルを加算的に読み込みます。
Unlike LoadLevel, LoadLevelAdditive does not destroy objects in the current level. Objects from the new
level are added to the current Scene. This is useful for creating continuous virtual worlds, where more
content is loaded in as you walk through the environment.
LoadLevelAdditive は、次のフレームの初回の FixedUpdate の呼び出しが行われる前に初期化が行われ、新しいオブジェクトが追加されます(イベント関数の実行順 を参照してください)。
See Also: AsyncOperation, Application.backgroundLoadingPriority, Application.LoadLevelAdditiveAsync, Application.LoadLevel, Application.LoadLevelAsync.