%!TEX root = ../../article.tex
\begin{tikzpicture}[traces]
\begin{scope}[yshift=-3cm]

\begin{pgfonlayer}{background} 
	\fill[black!20] (-3,-10) rectangle (7,16);
\end{pgfonlayer} 

\clip (-3,-10) rectangle (7,16);

\begin{scope}
	\filldraw[unshaded] (0,3) .. controls ++(-157:3cm) and ++(157:3cm) .. (0,-3) .. controls ++(112:2cm) and ++(-112:2cm) .. (0,3);
	\filldraw[unshaded] (0,3) .. controls ++(-22:3cm) and ++(22:3cm) .. (0,-3) .. controls ++(67:2cm) and ++(-67:2cm) .. (0,3);

\begin{scope}[yshift=6cm]
	\filldraw[unshaded] (0,3) .. controls ++(-157:3cm) and ++(157:3cm) .. (0,-3) .. controls ++(112:2cm) and ++(-112:2cm) .. (0,3);
	\filldraw[unshaded] (0,3) .. controls ++(-22:3cm) and ++(22:3cm) .. (0,-3) .. controls ++(67:2cm) and ++(-67:2cm) .. (0,3);
\end{scope}
	
	\filldraw[unshaded] (0,9) .. controls ++(22:3cm) and ++(90:4cm) .. (3,3) .. controls ++(-90:4cm) and ++(-22:3cm) .. (0,-3) .. controls ++(-67:6cm) and ++(-90:5cm) .. (4,3) .. controls ++(90:5cm) and ++(67:6cm) .. (0,9);
	\filldraw[unshaded] (0,9) .. controls ++(112:4cm) and ++(90:15cm) .. (5,3) .. controls ++(-90:15cm) and ++(-112:4cm) .. (0,-3) .. controls ++(-157:7cm) and ++(-90:20cm) .. (6,3) .. controls ++(90:20cm) and ++(157:7cm) .. (0,9);
	
	\node at (0,3) [Tbox] (T1) {$S$};
	\node at (0,9) [Tbox] (T3) {$S$};
	\node at (0,-3) [Tbox] (T2) {$S$};
	\node at (T1.100) [above left] {$\star$};
	\node at (T2.100) [above left] {$\star$};
	\node at (T3.90) [above left] {$\star$};

\end{scope}
\end{scope}
\end{tikzpicture}