La mejor manera de conectar 2 nodos con una ruta que rodea otro nodo

Question

Imagine el siguiente MWE:

\documentclass{article}

\usepackage{tikz}

\begin{document}
\begin{tikzpicture}

\node [draw, circle, minimum width=1cm] at (0,0)  (n1) {n1};
\node [draw, circle, minimum width=1cm] at (3,-1) (n2) {n2};
\node [draw, circle, minimum width=1cm] at (4,0)  (n3) {n3};

\path [in = 270, out = 0] (n1) edge (n3);

\end{tikzpicture}
\end{document}

¿Cómo se puede controlar correctamente la ruta para rodear el nodo n2? Sé que hay varios métodos, usando un auxiliar coordinateo con controls, pero no estoy seguro de cuál daría un mejor resultado.

Answer 1

A continuación muestro dos posibilidades; uno usando la .. controls ..sintaxis, y el otro, usando el through pointestilo implementado enAndrew Stacey's answeraConecte nodos automáticamente sin superponerse a otros nodos o conexiones. Decidir cuál da mejores resultados dependerá de varios factores (y algunos de ellos subjetivos):

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}

\makeatletter
% code by Andrew Stacey: https://tex.stackexchange.com/a/27996/3954
\tikzset{
  through point/.style={
    to path={%
      \pgfextra{%
        \tikz@scan@one@point\pgfutil@firstofone(\tikztostart)\relax
        \pgfmathsetmacro{\pt@sx}{\pgf@x * 0.03514598035}%
        \pgfmathsetmacro{\pt@sy}{\pgf@y * 0.03514598035}%
        \tikz@scan@one@point\pgfutil@firstofone#1\relax
        \pgfmathsetmacro{\pt@ax}{\pgf@x * 0.03514598035 - \pt@sx}%
        \pgfmathsetmacro{\pt@ay}{\pgf@y * 0.03514598035 - \pt@sy}%
        \tikz@scan@one@point\pgfutil@firstofone(\tikztotarget)\relax
        \pgfmathsetmacro{\pt@ex}{\pgf@x * 0.03514598035 - \pt@sx}%
        \pgfmathsetmacro{\pt@ey}{\pgf@y * 0.03514598035 - \pt@sy}%
        \pgfmathsetmacro{\pt@len}{\pt@ex * \pt@ex + \pt@ey * \pt@ey}%
        \pgfmathsetmacro{\pt@t}{(\pt@ax * \pt@ex + \pt@ay * \pt@ey)/\pt@len}%
        \pgfmathsetmacro{\pt@t}{(\pt@t > .5 ? 1 - \pt@t : \pt@t)}%
        \pgfmathsetmacro{\pt@h}{(\pt@ax * \pt@ey - \pt@ay * \pt@ex)/\pt@len}%
        \pgfmathsetmacro{\pt@y}{\pt@h/(3 * \pt@t * (1 - \pt@t))}%
      }
      (\tikztostart) .. controls +(\pt@t * \pt@ex + \pt@y * \pt@ey, \pt@t * \pt@ey - \pt@y * \pt@ex) and +(-\pt@t * \pt@ex + \pt@y * \pt@ey, -\pt@t * \pt@ey - \pt@y * \pt@ex) .. (\tikztotarget)
    }
  }
}

\makeatother


\begin{document}

\begin{tikzpicture}
\node [draw, circle, minimum width=1cm] at (0,0)  (n1) {n1};
\node [draw, circle, minimum width=1cm] at (3,-1) (n2) {n2};
\node [draw, circle, minimum width=1cm] at (4,0)  (n3) {n3};
\path [through point=(n2.east)] (n1) edge (n3);
\begin{scope}[xshift=6cm]
\node [draw, circle, minimum width=1cm] at (0,0)  (n1) {n1};
\node [draw, circle, minimum width=1cm] at (3,-1) (n2) {n2};
\node [draw, circle, minimum width=1cm] at (4,0)  (n3) {n3};
\draw (n1) .. controls ([yshift=-13pt]n2.south west) and ([yshift=-33pt]n2.south east) .. (n3);
\end{scope}
\end{tikzpicture}

\end{document}