Make a TikZ picture automatic

Question

I'm trying to make this picture in TikZ:

.

I wrote

\documentclass{standalone}
\usepackage{tikz}

\newcommand*{\rinn}{2}
\newcommand*{\rout}{3.8}
\newcommand*{\tangle}{37}
\newcommand*{\sangle}{-30}

\begin{document}
\begin{tikzpicture}
\coordinate [label=above:$T_1$]        (T1) at (\tangle:\rinn);
\coordinate [label=above right:$T_2$]  (T2) at (\tangle:\rout);
\coordinate [label=below right:$S_1$]  (S1) at (\sangle:\rinn);
\coordinate [label=below right:$S_2$]  (S2) at (\sangle:\rout);

\draw (0,0) circle [radius=\rinn];
\draw (0,0) circle [radius=\rout];

\draw (0,0) -- (T2);
\draw (0,0) -- (S2);

\end{tikzpicture}
\end{document}

that looks like

.

The image is automatic but the label position needs adjustment every time something is changed, and even then they're not well placed.

Is \newcommand the best way to define a variable for TikZ?
Is there a way to adjust the label position so that it always stays clear of the other lines?

You can visit at the link: http://tex.stackexchange.com/questions/58878/tikz-set-node-label-position-more-precisely or http://tex.stackexchange.com/questions/153391/adjust-position-of-node-label. — Sebastiano, Jan 09 '17 at 21:50
If you put the labels into separate nodes you will have more flexibility in placement, but automating the placement would require some non-trivial logic. — John Kormylo, Jan 09 '17 at 22:05
What are the domains of variability of your four parameters? — Paul Gaborit, Jan 09 '17 at 22:52
@PaulGaborit The radii are big enough as they are. I thought it would be easy to have the angles take any value but they shouldn't have to go past 90 or -90. — Kurzd, Jan 09 '17 at 23:04
@PaulGaborit Not exactly constant, but they could diminish to maybe to 80% of their current length. — Kurzd, Jan 09 '17 at 23:12
@Kruzd Some constraints as (\sangle < \tangle) or (\rinn < \rout) ? — Paul Gaborit, Jan 09 '17 at 23:17
@PaulGaborit 10 < \tangle < 80 and 280 < \sangle < 350 would make the output similar to the original image. \rinn < \rout, of course. — Kurzd, Jan 09 '17 at 23:23

score 7 · Accepted Answer · answered Jan 09 '17 at 23:42

7

Here is a possible solution:

\documentclass[tikz]{standalone}
\begin{document}
\foreach {\tangle} in {80,79,...,10}{
  \pgfmathsetmacro{\sangle}{-\tangle}
  \begin{tikzpicture}[auto]
    % constants
    \def\rinn{2}
    \def\rout{3.8}

    % just to fix the global bounding box
    \path circle[radius=\rout cm+5mm+2em];

    \draw (0,0) circle [radius=\rinn];
    \draw (0,0) circle [radius=\rout];

    \coordinate (T1) at (\tangle:\rinn);
    \coordinate (T2) at (\tangle:\rout);
    \coordinate (S1) at (\sangle:\rinn);
    \coordinate (S2) at (\sangle:\rout);

    \draw (0,0) -- (T1) -- (T2);
    \draw (0,0) -- (S1) -- (S2);

    \path (T1) ++(\tangle+45:5mm) node{T1};
    \path (T2) ++(\tangle+45:5mm) node{T2};
    \path (S1) ++(\sangle-45:5mm) node{S1};
    \path (S2) ++(\sangle-45:5mm) node{S2};

  \end{tikzpicture}
}
\end{document}

answered Jan 09 '17 at 23:42

Paul Gaborit

70,770
10
176
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That's way better than I originally expected. I compiled that, and got a 71-page document in qpdfview. How did you get that gif? You got a white border with \path circle[radius=\rout cm+5mm+2em]; instead of \documentclass[tikz,border=5mm+2em]{standalone}, and defined the radii with \def instead of \newcommand*. Are these personal preferences? – Kurzd Jan 09 '17 at 23:58
1

@Kurzd My fake circle adds a constant bounding box (the border option enlarges the bounding box). With \def, I can define a local macro event if it is always defined. With \newcommand, you may use \renewcommand... – Paul Gaborit Jan 10 '17 at 00:45
1

@Kurzd To make the gif, I use convert (from ImageMagick): convert -delay 0 -density 120 doc.pdf doc.gif – Paul Gaborit Jan 10 '17 at 00:47

score 1 · Answer 2 · answered Jan 09 '17 at 22:22

Not perfect solution ...

\documentclass[tikz,border=3mm]{standalone}
\usepackage{}

\newcommand*{\rinn}{2}
\newcommand*{\rout}{3.8}
\newcommand*{\tangle}{37}
\newcommand*{\sangle}{-30}

\begin{document}
\begin{tikzpicture}[auto]
\coordinate (T1) at (\tangle:\rinn);
\coordinate [label=\tangle:$T_2$]  (T2) at (\tangle:\rout);
\coordinate (S1) at (\sangle:\rinn);
\coordinate [label=\sangle:$S_2$]  (S2) at (\sangle:\rout);

\draw (0,0) circle [radius=\rinn];
\draw (0,0) circle [radius=\rout];

\draw (0,0) -- (T1) -- node[near start] {T1}  (T2);
\draw (0,0) -- (S1) -- node[near start] {S1}   (S2);

\end{tikzpicture}
\end{document}

Had no idea the border and tikz options existed. – Kurzd Jan 09 '17 at 23:36 — Kurzd, Jan 09 '17 at 23:36

Make a TikZ picture automatic

2 Answers2