Dotted lines in TikZ with round dots

Question

Well, the title explains all, I guess. Sorry if this is too simple for all the TikZ gurus here: but I want a dash pattern like "dotted" for drawning but with round dots and not the little squares. How can I achieve this in a simple way?

Answer 1

You could define a custom dash pattern with an on length of 0pt. If you set line cap=round, you'll end up with perfect circles. The dash pattern approach is much faster than using decorations for the same purpose.

\documentclass{article}

\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
\draw [line width=3pt, line cap=round, dash pattern=on 0pt off 2\pgflinewidth] (0,0) -- (3,0) to [out=0, in=0, looseness=2] (3,-1);
\end{tikzpicture}

\end{document}

---

The whole thing can of course be made into a new style so you just have to use dots, and which allows you to comfortably set the dot diameter using dot diameter and the dot spacing using dot spacing

\draw [dots] ...

\draw [red, dot diameter=5pt, dot spacing=5pt, dots] ...

\documentclass{article}

\usepackage{tikz}

\begin{document}

\makeatletter
\tikzset{
    dot diameter/.store in=\dot@diameter,
    dot diameter=3pt,
    dot spacing/.store in=\dot@spacing,
    dot spacing=10pt,
    dots/.style={
        line width=\dot@diameter,
        line cap=round,
        dash pattern=on 0pt off \dot@spacing
    }
}
\makeatother

\begin{tikzpicture}
\draw [dots] (0,0) -- (3,0) to [out=0, in=0, looseness=2] (3,-1);
\end{tikzpicture}

\begin{tikzpicture}
\draw [red, dot diameter=5pt, dot spacing=5pt, dots] (0,0) -- (3,0) to [out=0, in=0, looseness=2] (3,-1);
\end{tikzpicture}

\end{document}

Answer 2

Another possibility is to exploit the decorations libraries as Lionel suggested: one example presented will be based on decorations.markings while the other one on decorations.shapes.

Decorations.markings

The code:

\documentclass[png,tikz,border=3pt]{standalone}
\usepackage{tikz} 
\usetikzlibrary{decorations.markings}

\pgfkeys{/tikz/.cd,
  circle color/.initial=black,
  circle color/.get=\circlecolor,
  circle color/.store in=\circlecolor,
}

\tikzset{dotted pattern/.style args={#1 and #2}{
   postaction=decorate,
   decoration={
    markings,
    mark=
    between positions 0 and 1 step #2
      with
      {
       \fill[radius=#1,\circlecolor] (0,0) circle;
      }
    }
  },
  dotted pattern/.default={1pt and 1.5mm},
}

\begin{document}
\begin{tikzpicture}
\path [dotted pattern] 
  (0,0) -- (3,0) to [out=0, in=0, looseness=2] (3,-1);
\end{tikzpicture}

\begin{tikzpicture}
\path [circle color=red,
   dotted pattern=1.5pt and 4mm] 
  (0,0) -- (3,0) to [out=0, in=0, looseness=2] (3,-1);
\end{tikzpicture}
\end{document}

provides:

and

Indeed, with the dotted pattern style you can customize the radius and the distance between the circles respectively while with the circle color key you may change the color.

Decorations.shapes

The code:

\documentclass[png,tikz,border=3pt]{standalone}
\usepackage{tikz} 
\usetikzlibrary{decorations.shapes}

\pgfkeys{/tikz/.cd,
  circle color/.initial=black,
  circle color/.get=\circlecolor,
  circle color/.store in=\circlecolor,
}

\tikzset{dotted pattern/.style args={#1 and #2}{
   decorate,
   fill=\circlecolor,
   decoration={
    shape backgrounds,
    shape=circle,
    shape size=#1,
    shape sep={#2, between center}, 
    }
  },
  dotted pattern/.default={1pt and 1.5mm},
}

\begin{document}
\begin{tikzpicture}
\path [dotted pattern] 
  (0,0) -- (3,0) to [out=0, in=0, looseness=2] (3,-1); 
\end{tikzpicture}

\begin{tikzpicture}
\path [circle color=red,
   dotted pattern=1.5pt and 4mm] 
  (0,0) -- (3,0) to [out=0, in=0, looseness=2] (3,-1);
\end{tikzpicture}
\end{document}

The result are still the pictures shown above. In order to use \draw rather than \path, one might add a draw=none to the dotted pattern style.