How to circle a complex set of nodes and fill the surface

Question

I'm trying to circle a set of nodes in a graph in such way that it is nice and I can fill the surface.

I've tried plot[smooth cycle] but is leads to mitigated results. I've also tried to use \shade and \fill but I think my border paths are not connected very well...

Could you give me some ideas?

Here is the graph and the kind of circle I would like to get.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows,automata,calc}

\begin{document}
\begin{figure}
\footnotesize
\begin{tikzpicture}[->,>=stealth',auto,semithick]

    \tikzstyle{every state}=[fill=none,draw=black,text=black]
    \tikzset{ficti/.style={draw=none,text=black,fill=none}}
    \tikzset{mycut/.style={thick,double,-}}

    \node[state,fill=gray] (SRC) [] {$src$};
    \node[state,node distance=1.60cm] (S10) [right of=SRC] {$1_0$};
    \node[state,node distance=1.20cm] (S20) [below of=S10] {$2_0$};
    \node[state,node distance=1.20cm] (S30) [below of=S20] {$3_0$};
    \node[state,node distance=1.20cm] (S40) [below of=S30] {$4_0$};
    \node[state,node distance=1.90cm] (S21) [right of=S20] {$2_1$};
    \node[state,node distance=1.90cm] (S31) [right of=S30] {$3_1$};
    \node[state,node distance=1.90cm] (S22) [right of=S21] {$2_2$};
    \node[state,node distance=1.90cm] (S32) [right of=S31] {$3_2$};
    \node[state,node distance=5.70cm] (S41) [right of=S40] {$4_1$};
    \node[state,node distance=1.90cm] (S42) [right of=S41] {$4_2$};
    \node[ficti,node distance=4.70cm] (F01) [right of=S10] {};
    \node[state,node distance=0.50cm] (S50) [above of=F01] {$5_0$};
    \node[state,node distance=1.90cm] (S51) [right of=S50] {$5_1$};
    \node[state,node distance=1.90cm] (S52) [right of=S51] {$5_2$};
    \node[state,node distance=5.20cm,fill=gray] (SNK) [right of=F01] {$snk$};

    \draw[mycut] (SRC) ++(90:15pt) coordinate(a1) arc (90:260:15pt) coordinate(a2);
    \draw[mycut] (S20) ++(30:15pt) coordinate(b1) arc (30:85:15pt) coordinate(b2);
    \draw[mycut] (S31) ++(210:15pt) coordinate(c1) arc (210:270:15pt) coordinate(c2);
    \draw[mycut] (S41) ++(60:15pt) coordinate(d1) arc (60:90:15pt) coordinate(d2);
    \draw[mycut] (S42) ++(-115:15pt) coordinate(e1) arc (-115:60:15pt) coordinate(e2);
    \draw[mycut] (a2) to (b2);
    \draw[mycut] (b1) to (c1);
    \draw[mycut] (c2) to (d2);
    \draw[mycut] (d1) to (e1);
    \draw[mycut] plot [smooth] coordinates {(e2) ($(S10)!0.5!(S22)+(0.7,0.70)$) (a1)};

\end{tikzpicture}
\end{figure}
\end{document}

results

Welcome to TeX.SE! Do you want to fill that whole area delimited by the plot? — Alenanno, Jun 24 '15 at 08:25
Welcome to TeX.SX! Usually, we don't put a greeting or a “thank you” in our posts. While this might seem strange at first, it is not a sign of lack of politeness, but rather part of our trying to keep everything very concise. Accepting and upvoting answers is the preferred way here to say “thank you” to users who helped you. — Martin Schröder, Jun 24 '15 at 08:27
@MaartenDhondt The hull is not convex here. It won't cover this case. — percusse, Jun 24 '15 at 09:01

score 3 · Accepted Answer · answered Jun 24 '15 at 08:57

If you want to fill that area, you're better off using a single draw command and then filling that. Having multiple paths makes it only harder to fill because you need to fill each one of them and you're not even guaranteed a good result anyways.

Some notes:

You only need one \tikzset and then you can group styles inside of it. Also, keep using it instead of \tikzstyle.
arrows is considered deprecated (although still supported for those that want to stick with it), so I replaced it with arrows.meta. The syntax for arrow tips is a slightly different, but not totally. See the Tikz Manual for more information.

Output

Code

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,automata,calc, backgrounds}

\tikzset{
    every state/.style={fill=none,draw=black,text=black},
    ficti/.style={draw=none,text=black,fill=none},
    mycut/.style={thick,double,-}
}

\begin{document}
\begin{figure}
\footnotesize
\begin{tikzpicture}[->,-{Stealth},auto,semithick]


    \node[state,fill=gray] (SRC) [] {$src$};
    \node[state,node distance=1.60cm] (S10) [right of=SRC] {$1_0$};
    \node[state,node distance=1.20cm] (S20) [below of=S10] {$2_0$};
    \node[state,node distance=1.20cm] (S30) [below of=S20] {$3_0$};
    \node[state,node distance=1.20cm] (S40) [below of=S30] {$4_0$};
    \node[state,node distance=1.90cm] (S21) [right of=S20] {$2_1$};
    \node[state,node distance=1.90cm] (S31) [right of=S30] {$3_1$};
    \node[state,node distance=1.90cm] (S22) [right of=S21] {$2_2$};
    \node[state,node distance=1.90cm] (S32) [right of=S31] {$3_2$};
    \node[state,node distance=5.70cm] (S41) [right of=S40] {$4_1$};
    \node[state,node distance=1.90cm] (S42) [right of=S41] {$4_2$};
    \node[ficti,node distance=4.70cm] (F01) [right of=S10] {};
    \node[state,node distance=0.50cm] (S50) [above of=F01] {$5_0$};
    \node[state,node distance=1.90cm] (S51) [right of=S50] {$5_1$};
    \node[state,node distance=1.90cm] (S52) [right of=S51] {$5_2$};
    \node[state,node distance=5.20cm,fill=gray] (SNK) [right of=F01] {$snk$};

\begin{scope}[on background layer]
\filldraw[mycut, top color=cyan!50, bottom color=blue!50!black] (SRC) ++(90:15pt) coordinate(a1)
        arc (90:260:15pt) 
        -- ($(S20)+(90:15pt)$)
        arc (85:30:15pt)
        -- ($(S31)+(210:15pt)$)
        arc (210:270:15pt)
        -- ($(S41)+(90:15pt)$)
        arc (90:60:15pt)
        -- ($(S42)+(-115:15pt)$)
        arc (-115:60:15pt) [rounded corners=1cm]
        -- (S21.east|-a1) [sharp corners] -- cycle;
\end{scope}
\end{tikzpicture}
\end{figure}
\end{document}

How to circle a complex set of nodes and fill the surface

1 Answers1

Output

Code