static void ShowWindow()
    {
        TransferFunctionEditorWindow tf1dWnd = (TransferFunctionEditorWindow)EditorWindow.GetWindow(typeof(TransferFunctionEditorWindow));

        if (tf1dWnd != null)
        {
            tf1dWnd.Close();
        }

        TransferFunction2DEditorWindow tf2dWnd = (TransferFunction2DEditorWindow)EditorWindow.GetWindow(typeof(TransferFunction2DEditorWindow));

        tf2dWnd.Show();
    }