Draw circular lines between tikz nodes

Question

Consider the following MWE:

\documentclass[tikz]{standalone}
\begin{document}
  \usetikzlibrary{shapes}
  \tikzset{every picture/.append style={auto,
      line width=1pt, >=stealth,  font=\small}}
  \begin{tikzpicture}[x=1mm,y=1mm]%
       \node[ellipse,draw,align=left] at (65:40mm) (AA){citric\acid};
    \node[ellipse,draw,align=left] at (20:40)(BB){ISOcitric\acid};
    \node[ellipse,draw,align=left] at (335:40)(CC)
                     {( \alpha )-ketoglu-\taric acid};
    \node[ellipse,draw,align=left] at (290:40)(DD){succinyl-\CoA};
    \node[ellipse,draw,align=left] at (245:40)(EE){succinate};
    \node[ellipse,draw,align=left] at (200:40)(FF){fumarate};
    \node[ellipse,draw,align=left] at (155:40)(GG){malate};
    \node[ellipse,draw,align=left] at (110:40)(HH){oxalo-\acetate};
\draw[-&gt;](AA) to[bend left=15](BB);
\draw[-&gt;](BB) to[bend left=15](CC);
\draw[-&gt;](CC) to[bend left=15](DD);
\draw[-&gt;](DD) to[bend left=15](EE);
\draw[-&gt;](EE) to[bend left=15](FF);
\draw[-&gt;](FF) to[bend left=15](GG);
\draw[-&gt;](GG) to[bend left=15](HH);
\draw[-&gt;](HH) to[bend left=15](AA);


\end{tikzpicture}
\end{document}

Many of you will recognize this as the start of a description of the citric acid cycle. I find it acceptable, but it would be even better if the lines with the arrows between the nodes actually followed the circle that was implicitly used to place the nodes.

How can this be done?

Q511183 and many of the linked Qs. – Qrrbrbirlbel Apr 19 '23 at 15:07 — Qrrbrbirlbel, Apr 19 '23 at 15:07

score 2 · Answer 1 · answered Apr 20 '23 at 10:46

A simplification, making all the nodes circles.

\documentclass[tikz,border=1.618]{standalone}
\begin{document}
\begin{tikzpicture}
% dimensions:
\def\br{4.5} % big  radius
\def\lr{0.9} % node radius
% intersection point and angle:
\pgfmathsetmacro\x{\br-0.5\lr\lr/\br}
\pgfmathsetmacro\y{sqrt(\br\br-\x\x))}
\pgfmathsetmacro\sa{atan(\y/\x)}
% only for comparison:
\draw[gray,very thin] (0,0) circle (\br);
% diagram:
\foreach[count=\i]\j in {ISOcitric\acid,citric\acid,oxalo-\acetate,malate,
                         succinate,fumarate,succinyl-\CoA,(\alpha)-ketoglu-\taric acid}
{
  \begin{scope}[rotate=45*\i-22.5]
    \draw[thick] (\br,0) circle (\lr);
    \node[text width=2cm,align=center] at (\br,0) {\j};
    \draw[latex-,thick] (\sa:\br) arc (\sa:45-\sa:\br);
  \end{scope}
}
\end{tikzpicture}
\end{document}

score 0 · Answer 2 · answered Apr 29 '23 at 15:07

After studying the tikz manual for some time, i found the property 'looseness', which can be applied to 'bend left'. The result is as follows, with the thick red circle as a help circle.

\documentclass[tikz]{standalone}
\begin{document}
  \usetikzlibrary{shapes}
  \tikzset{every picture/.append style={auto,
      line width=1pt, >=stealth,  font=\small}}
  \begin{tikzpicture}[x=1mm,y=1mm]%
    \drawred!40,line width=2ptcircle[radius=40mm];
    \node[ellipse,draw,align=left] at (65:40mm) (AA){citric\acid};
    \node[ellipse,draw,align=left] at (20:40)(BB){ISOcitric\acid};
    \node[ellipse,draw,align=left] at (335:40)(CC)
    {( \alpha )-ketoglu-\taric acid};
    \node[ellipse,draw,align=left] at (290:40)(DD){succinyl-\CoA};
    \node[ellipse,draw,align=left] at (245:40)(EE){succinate};
    \node[ellipse,draw,align=left] at (200:40)(FF){fumarate};
    \node[ellipse,draw,align=left] at (155:40)(GG){malate};
    \node[ellipse,draw,align=left] at (110:40)(HH){oxalo-\acetate};
\draw[-&gt;](AA) to[bend left=15,looseness=0.7](BB);
\draw[-&gt;](BB) to[bend left=15,looseness=0.7](CC);
\draw[-&gt;](CC) to[bend left=15,looseness=0.7](DD);
\draw[-&gt;](DD) to[bend left=15,looseness=0.7](EE);
\draw[-&gt;](EE) to[bend left=15,looseness=0.9](FF);
\draw[-&gt;](FF) to[bend left=15](GG);
\draw[-&gt;](GG) to[bend left=15,looseness=0.9](HH);
\draw[-&gt;](HH) to[bend left=15,looseness=0.7](AA);


\end{tikzpicture}
\end{document}

The result is as follows:

Draw circular lines between tikz nodes

2 Answers2