# Example: Commutative diagram with crossing edges

Published 2011-12-16 | Author: Stefan Kottwitz
Source: TeXblog

When one edge of a graph passes over or under another edge there may be a small gap needed in the drawing of one of those edges. An easy trick is to draw the upper edge two times: first with the background color and more thickness, afterwards normally. This is an example diagram used in the definition of the pull-back of a Banach bundle.

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% Commutative diagram with edges passing under/over
% Jan 7, 2009, Stefan Kottwitz
% http://texblog.net
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}
\begin{tikzpicture}
\matrix (m) [matrix of math nodes, row sep=3em,
column sep=3em]{
& f^\ast E_V& & \vphantom{f^\ast}E_V \\
f^\ast E & & \vphantom{f^\ast}E & \\
& U & & V \\
M & & N & \\};
\path[-stealth]
(m-1-2) edge (m-1-4) edge (m-2-1)
edge [densely dotted] (m-3-2)
(m-1-4) edge (m-3-4) edge (m-2-3)
(m-2-1) edge [-,line width=6pt,draw=white] (m-2-3)
edge (m-2-3) edge (m-4-1)
(m-3-2) edge [densely dotted] (m-3-4)
edge [densely dotted] (m-4-1)
(m-4-1) edge (m-4-3)
(m-3-4) edge (m-4-3)
(m-2-3) edge [-,line width=6pt,draw=white] (m-4-3)
edge (m-4-3);
\end{tikzpicture}
\end{document}