tikz-pgf
TikZ allows regular polygons with specified number of sides for nodes. I'm using PGF though and want similar features and to be able to create my own custom shapes.
See percusse's answer for example code:
and
http://www.texample.net/tikz/examples/node-shapes/
for the polygons.
What I would like is to be able to create a reference shape like rpoly7 that is simply a regular polygon with 7 sides that uses the TikZ shapes but can be passed to PGF like I do with the other shapes.
I do not know of a central repository, however, there are a lot of examples at TeXample
Regular polygons can be drawn after loading the shapes.geometric library by using something like \node (<name>) [regular polygon, regular polygon sides=5, draw] {} for a pentagon. The corners of the polygon are then available as (<name>.corner <n>), and the midpoints of the sides as (<name>.side <n>).
To reflect the corners along a line coincident with a side, you can use a combination of two TikZ functions: The let syntax, which allows you to temporarily store a point in a macro, and the calc library, with which you can perform coordinate calculations.
Here's a pentagon with the corners labeled:
\node (A) [draw,regular polygon, regular polygon sides=5, minimum size=2cm,outer sep=0pt] {};
\foreach \n in {1,...,5} {
\node at (A.corner \n) [anchor=360/5*(\n-1)+270] {\scriptsize\texttt{A.corner \n}};
}
Now say you want to mirror corner 4 on the line passing through corner 1 and corner 2. TikZ doesn't provide a mirror operation directly, but you can use the projection syntax for this. Coordinate calculation expressions are surrounded by ($...$), and the projection syntax is (<first coordinate)!(<projection coordinate>)!(<second coordinate>), so the projection of corner 4 on the line passing through corners 1 and 2 can be expressed as
($(A.corner 1)!(A.corner 4)!(A.corner 2)$)
If we call that point Q, the reflection of corner 4 (let's call that point C4) can be expressed as C4' = Q - (C4 - Q) = 2*Q - C4. In TikZ notation, this would look like
($ 2*($(A.corner 1)!(A.corner 4)!(A.corner 2)$) - (A.corner 4) $)
In order to do this for all corners of the polygon, we can use a \foreach loop. To make the code a little more readable, the points A.corner 1 and A. corner 2 can be saved into temporary macros using the let syntax. Finally, the whole thing can be wrapped into a TikZ style.
The lines
\node (A) [polygon=5, thick] {};
\draw [blue,mirror polygon=1];
\draw [orange,mirror polygon=2];
\draw [red,mirror polygon=3];
\draw [cyan,mirror polygon=4];
\draw [purple,mirror polygon=5];
will yield
and the lines
\node (A) [polygon=3, thick] {};
\draw [blue,mirror polygon=1];
\draw [orange,mirror polygon=2];
\draw [red,mirror polygon=3];
will yield
Here's the complete code:
\documentclass[border=5mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric, calc}
\begin{document}
\begin{tikzpicture}
\tikzset{
polygon n/.code=\gdef\polygonN{#1}, % Save N in a global macro
polygon/.style={
regular polygon,
regular polygon sides=#1,
polygon n=#1,
draw,
minimum size=2cm,
outer sep=0pt
},
mirror polygon/.style={
insert path={
let \p1 = (A.corner #1),
\p2 = (A.side #1) in (\p1)
($ 2*($(\p1)!(A.corner 1)!(\p2)$) - (A.corner 1) $) % Path needs to be started before the foreach
\foreach \n in {2,...,\polygonN} {
-- ($ 2*($(\p1)!(A.corner \n)!(\p2)$) - (A.corner \n) $)
} -- cycle
}
}
}
\node (A) [polygon=5, thick] {};
\draw [blue,mirror polygon=1];
\draw [orange,mirror polygon=2];
\draw [red,mirror polygon=3];
\draw [cyan,mirror polygon=4];
\draw [purple,mirror polygon=5];
\end{tikzpicture}
\end{document}
Best Answer
The
regular polygonshape is not a "TikZ shape" (and neither are any of the other predefined shapes), they're all "PGF shapes". General rule: If the relevant keys in thepgfmanualinclude the/pgfdirectory, they're PGF keys. To set the parameters likeregular polygon sides, you have to call\pgfkeys{/pgf/<option>=<value}: