Draw reversed path in TikZ

Question

Is there a way to draw a TikZ path reversed?

I am trying to create some code that generates tessellating figures (to be used in How do we Draw a Bird in LaTeX).

Here is what I got:

\documentclass{minimal}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\def\x{2}
\def\y{4}
\def\mypath{(0,0) -- (1,1) -- (\x,0) -- (\x,\y)}
\draw \mypath;
\draw[shift={(\x,\y)}, rotate=180, blue] \mypath;
\end{tikzpicture}
\end{document}

It generates this: wrong But what I wanted is this:. So it is obviously not correct to rotate the path. I need to break it into two an draw it reversed.

If you just put the URL of a question in your post, it'll be converted to the question title automatically, as can be seen in my edit. — doncherry, Mar 17 '12 at 22:55
The shape is already defined in the shape library with the name signal. Check the manual page 439. — percusse, Mar 17 '12 at 23:43
@percusse: I am trying to generate tessellating figures. I do not want to draw this specific shape. — hpekristiansen, Mar 17 '12 at 23:58
I don't see how "drawing it reversed" (whatever that actually means) gives you the result you want. You seem to want to get a path that is reflected in x everywhere, and reflected in y half of the time. Perhaps you should draw a different part of the path and reflect that (since you want the reflection over the x axis everywhere, I suggest drawing either the left or right hand side and mirroring that). Perhaps I am just misunderstanding you, it's not terribly clear. — Roelof Spijker, Mar 18 '12 at 00:35
Yes, but they are not symmetric (a slight smell of group theory, yuck!). In other words they don't fit together to form a shape that you want. — percusse, Mar 18 '12 at 00:43

Alain Matthes · Accepted Answer · 2012-03-18T14:10:42.900

It's not possible with the definition of \mypath

enter image description here

\documentclass{minimal}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}
  \def\x{2}
  \def\y{4}
  \def\mypath{(0,0) -- (1,1) -- (\x,0) -- (\x,\y)}
  \draw[red] \mypath;
\end{tikzpicture}
\hspace{1cm}
\begin{tikzpicture}
  \def\x{2}
  \def\y{4}
  \def\mypath{(0,0) -- (1,1) -- (\x,0) -- (\x,\y)}
  \draw[rotate=180, blue] \mypath;
\end{tikzpicture}
\end{document}

There is no shift possible to complete correctly your shape

but with

\documentclass{minimal}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}
  \def\x{2}
  \def\y{4}
  \def\mypath{((1,1) -- (\x,0) -- (\x,\y)--++(-1,1)}
  \draw[red] \mypath;
  \draw[blue,x=-0.5*\x cm,xshift=\x cm]  \mypath; 
\end{tikzpicture}

\end{document}

enter image description here

score 5 · Answer 2 · edited May 09 '12 at 07:40

A solution to what you are trying to attempt is as follows :

draw path forward
shift
draw path backwards
close path

To make this easier, don't specify the path by actual points, but rather by displacements. The code is

\documentclass[border=5pt]{standalone}

\usepackage{tikz}
\usetikzlibrary{calc}

\begin{document}
\begin{tikzpicture}

\coordinate (start) at (0,0);
\def\shape{{(1,1)},{(1,-1)}}
\coordinate (shift) at (0,4);

\foreach \point [count=\n] in \shape {
        \node[coordinate] (d-\n) at \point {};
        }
\pgfmathtruncatemacro{\size}{\n}

\draw (start) 
      \foreach \i in {1,...,\size} {-- ++(d-\i)} %draw forward
      -- ++(shift) %shift
      \foreach \i in {\size,...,1} {-- ++($-1*(d-\i)$)} % draw backward
      -- cycle; %close


\end{tikzpicture}
\end{document}

The result is

enter image description here

Draw reversed path in TikZ

2 Answers2