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I'm trying to draw a winding line like the solid black one in the following figures using tikz. However, I have no clue how to draw such a complex one.

Could anyone provide some suggestions?

Thanks ahead!

enter image description here

Update: I followed this thread, Spiral spring in TikZ, for generating the two spiral structures. Here is a snipet of my code

\documentclass[tikz,12pt]{standalone} % the code copied from the attached thread \newcommand\spiral{}% Just for safety so \def won't overwrite something \def\spiral[#1](#2)(#3:#4:#5){% \spiral[draw options](placement)(end angle:revolutions:final radius) \pgfmathsetmacro{\domain}{pi*#3/180+#4*2*pi} \draw [#1,line width=1pt, shift={(#2)}, domain=0:\domain,variable=\t,smooth,samples=int(\domain/0.08)] plot ({\t r}: {#5*\t/\domain}) } \begin{document} \begin{tikzpicture}[scale=1] % plot two spirals \spiral[black](8,1.6)(0:2:0.6); \spiral[black](8,1.6)(0:2:-0.6); \spiral[black](6.86, 1.00)(0:1:0.4); \spiral[black](6.86, 1.00)(0:1:-0.4); % connecting them \draw[black,line width=1pt] plot [smooth] coordinates {(7.18, 0.81) (7.26, 1) (7.4, 1.6) (7.43, 1.73) (7.48, 1.86)}; \draw[black,line width=1pt] plot [smooth] coordinates {(6.46, 1) (6.37, 0.84) (6.28, 0.69) (6.16, 0.57) (6.01, 0.47) (5.89, 0.41) (5.64, 0.34)}; \draw[black,line width=1pt] plot [smooth] coordinates {(8.6, 1.6) (8.64, 1.84) (8.69, 2.02) (8.77, 2.22)}; \end{tikzpicture} \end{document}

And here is what I got

enter image description here

To connect the two spirals, I digitized the picture and measured some coordinates, then used these coordinates to draw the lines between them. However, the connections are not smooth.

I know this is a stupid way to do it. Any suggestion for a better way to do this is mostly welcomed!

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    Please post a minimal example showing what you've tried. Right now, this is just a do-this-complicated-thing-for-me. Commented Sep 11, 2023 at 23:08
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    @cfr I added a MWE. Please take a look. Commented Sep 13, 2023 at 19:39
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    @projetmbc I added a MWE. Please take a look. Commented Sep 13, 2023 at 19:39
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    This takes you a considerable way towards your goal - great! There's a package called hobby which can help with drawing smooth curves through points. It's a bit slower, but I think it'd be worth using for something like this where smoothness really matters and is tricky to get right. Commented Sep 13, 2023 at 21:41
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    The best answer is not always the accepted one or the one with the most votes, especially when answers build on one another and/or some come much later. If you look at the other answer, you'll find the original code you've used gets expanded and parametised. That's easier to work with. In particular, you can get names for the start and end of the spirals. Plugging your numbers from above in, I can recreate the spirals more conveniently. Centring one on the origin will also make things easier. At least, i usually find that's helpful. Commented Sep 14, 2023 at 1:58

1 Answer 1

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enter image description here

I do a sketch of the big winding piece of the curve; there are some constants, but you will see, you can not really vary them, except for the radius.

The code

\documentclass[11pt, border=.5cm]{standalone} \usepackage{tikz} \usetikzlibrary{math} \begin{document} \begin{tikzpicture}[evaluate={% \aini = 45; % initial angle \aend = 19; % \r = 3; % radius \T = 1.5 +.12; % f\defines the number of turnings of one branch \c = .8; }] \draw[gray!40] (-5, -5) grid (5, 5); \draw[red!30] (0, 0) circle (\r); \draw[black, ultra thick] (-\aini: 3*\r) to[out={180 -\aini}, in=-\aini+2] (\aini: \r); \draw[black, ultra thick, variable=\t, domain=0:\T, samples=200] plot (\t*360 +\aini: {\r*(1 -\c*\t/\T)}) to[out=\aend, in=-\aini] (-\aini: 0); \draw[ultra thick, variable=\t, domain=0:\T, samples=200] plot (\t*360 +\aini +180: {\r*(1 -\c*\t/\T)}) to[out={180 +\aend}, in={180 -\aini}] (180 -\aini: 0); \draw[ultra thick] (180 -\aini: 3*\r) to[out=-\aini+2, in={180 -\aini}] (\aini +180: \r); \end{tikzpicture} \end{document}
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