# Draw between shapes in Tikz

I'm trying to draw lines from the center circle (General Assembly) to the Economic and Social Council and International Criminal Court circles such that the angle of incidence for the line on all three circles is 0 degrees, i.e., the line is at a 90 degree angle to the surface of the circle. Right now, this is what I have.

\documentclass{article}
\usetikzlibrary{calc}
\usetikzlibrary{matrix, shapes}
\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{snakes}
\usetikzlibrary{positioning, intersections}
\pgfplotsset{compat=1.10}
\begin{document}

\begin{figure}[H]
\label{fig:structure}
\centering
\begin{tikzpicture}
\node[xshift=6cm,draw,regular polygon, regular polygon sides=4,text width=3cm,align=center] (sa)
{{\Large Specialized agencies}:\\
\textbullet FAO\\
\textbullet ILO\\
\textbullet ITU\\
\textbullet WHO};
\node[minimum size= 4.5cm, xshift=12cm,draw,circle, text width=3cm,align=center] (ga) {\Large{General Assembly}\\
\small{1 nation, 1 vote}};
\node[xshift=12cm,yshift=-5cm,draw, circle, text width=3cm,align=center] (sc) {\Large Security Council\\
\small{5 permanent members\\
10 rotating members chosen by GA}};
\node[xshift=12cm,yshift=5cm,draw,circle, text width=3cm,align=center] (sg) {\Large Secretary General\\
\small{Supports GA decisions}};
\node[xshift=17cm,yshift=2cm,draw,circle, text width=3cm,align=center] (ecsoc) {\Large Economic and Social Council
};
\node[xshift=17cm,yshift=-2cm,draw,circle, text width=3cm,align=center] (icc) {\Large International Criminal Court
};
\draw (sa.east) -- (ga.west);
\draw (sg.south) -- (ga.north);
\draw (sc.north) -- (ga.south);
\draw (ga.east) -- (ecsoc.west);
\draw (ga.east) -- (icc.west);
\end{tikzpicture}
\caption{Structure of the United Nations}
\end{figure}

\end{document}


• Just take off the anchors or use center. Tikz knows to stop at the border. – John Kormylo Apr 20 '15 at 4:28
• Replace last five lines with \foreach \i in {sa,sc,icc,ecsoc,sg} \draw (ga)--(\i); – Ignasi Apr 20 '15 at 8:03
• If you want to draw a line "at a 90 degree angle to the surface of the circle" I think you need a 3D representation. And if you want a line "at a 90 degree angle to the border of the circle", I think that all lines going to circle center are valid. So I understand "the angle of incidence for the line on all three circles is 0 degrees" but not the "i.e.". – Ignasi Apr 20 '15 at 9:54

If you mean that they must be perpendicular to the circle border, then instead of --, use edge[out=0, in=180] such as in \draw (ga.east) edge[out=0, in=180] (ecsoc.west);. This way the line exits at 0 degrees (right) and enters at 180 (left).

Also, write the Tikz libraries all in one place, separated by comma, after you call the Tikz package so that it doesn't create errors. I usually list all the packages I need then the libraries when applicable after all of them. This way it's also easier to understand and more organized.

\documentclass{article}
\usepackage{tikz}
\usepackage{pgfplots}

\usetikzlibrary{positioning, intersections, calc, matrix, shapes, snakes}
\pgfplotsset{compat=1.10}

\begin{document}

\begin{figure}[H]
\label{fig:structure}
\centering
\begin{tikzpicture}
\node[xshift=6cm,draw,regular polygon, regular polygon sides=4,text width=3cm,align=center] (sa)
{{\Large Specialized agencies}:\\
\textbullet FAO\\
\textbullet ILO\\
\textbullet ITU\\
\textbullet WHO};
\node[minimum size= 4.5cm, xshift=12cm,draw,circle, text width=3cm,align=center] (ga) {\Large{General Assembly}\\
\small{1 nation, 1 vote}};
\node[xshift=12cm,yshift=-5cm,draw, circle, text width=3cm,align=center] (sc) {\Large Security Council\\
\small{5 permanent members\\
10 rotating members chosen by GA}};
\node[xshift=12cm,yshift=5cm,draw,circle, text width=3cm,align=center] (sg) {\Large Secretary General\\
\small{Supports GA decisions}};
\node[xshift=17cm,yshift=2cm,draw,circle, text width=3cm,align=center] (ecsoc) {\Large Economic and Social Council
};
\node[xshift=17cm,yshift=-2cm,draw,circle, text width=3cm,align=center] (icc) {\Large International Criminal Court
};
\draw (sa.east) -- (ga.west);
\draw (sg.south) -- (ga.north);
\draw (sc.north) -- (ga.south);
\draw (ga.east) edge[out=0, in=180] (ecsoc.west);
\draw (ga.east) edge[out=0, in=180] (icc.west);
\end{tikzpicture}
\caption{Structure of the United Nations}
\end{figure}

\end{document}


By the way, you can modify the curve appearance, by adding the key "looseness". The default is 1, 0 creates a straight line and increasing numbers accentuates the curve. Here's an example (the black one is the standard, or 1):

\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}

\usetikzlibrary{positioning, intersections, calc, matrix, shapes, snakes}
\pgfplotsset{compat=1.10}

\begin{document}

\begin{tikzpicture}
\node[draw, circle, text width=3cm, align=center] (ga) {\Large General Assembly};
\node[draw, circle, text width=3cm, align=center, xshift=6cm, yshift=3cm] (ecsoc) {\Large Economic and Social Council};

\draw[green] (ga.east) edge[out=0, in=180, looseness=0] (ecsoc.west);
\draw (ga.east) edge[out=0, in=180, looseness=1] (ecsoc.west);
\draw[red] (ga.east) edge[out=0, in=180, looseness=5] (ecsoc.west);
\draw[blue] (ga.east) edge[out=0, in=180, looseness=10] (ecsoc.west);

\end{tikzpicture}

\end{document}