/// <summary>
 /// Resets the session.
 /// This should be called by clients when a match ends
 /// and you plan on starting a new one, such as returning to lobby.
 /// </summary>
 public virtual void ResetSession()
 {
     currentFrame   = 0;
     uRollbackWorld = new URollbackWorld();
 }
 /// <summary>
 /// Deactivates the session.
 /// This should be called by clients when they disconnect,
 /// and by the server when it shuts down.
 /// </summary>
 public virtual void EndSession()
 {
     clients.Clear();
     uRollbackWorld = null;
     sessionActive  = false;
 }