[Tex/LaTex] TikZ/pgf: How to draw edges that start and end at the same node when using the `graphdrawing` library

tikz-pgf

I have borrowed this example from http://www.texample.net/.

enter image description here

The graph exhibits a characteristic that I do not know how to reproduce using the graphdrawing library: its nodes have edges that start and end at the same node. How would this be done when using the graphdrawing library?

Here's what I have tried so far. I attempted to force the edge length to be a certain amount, so that the algorithm would have to draw a edge with that length, but then also loop it back. It seems that this command does not force the edge to be a certain length, and thus produces a nonsense result.

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{graphdrawing}
\usetikzlibrary{arrows}
\usetikzlibrary{graphs}
\usegdlibrary{force, layered, trees}

\begin{document}


    \tikz [rounded corners]
        \graph [spring layout]
        {
            a ->
            {
                b ->[length=3] b
            }
        };

\end{document}

Best Answer

After seeing an example here, which showed how [bend right] could be used with edges in graphdrawing, I tried [loop right] similar to what the example I first presented does. Lo and behold, it works.

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{graphdrawing}
\usetikzlibrary{arrows}
\usetikzlibrary{graphs}
\usegdlibrary{force, layered, trees}

\begin{document}


    \tikz [rounded corners]
        \graph [spring layout]
        {
            a ->
            {
                b ->[loop right] b
            }
        };

\end{document}

enter image description here

Related Solutions

[Tex/LaTex] Faded drop-shadow using tikz-based rounded rectangle

You could use the pgf-blur package, which gives you this:

a rounded rectangle node with faded drop shadow

In fact, it can add a "faded" drop shadow to pretty much anything:

a slightly rounded tape node with faded drop shadow

The shadow fading is not continuous, like in the previously accepted answer. It fades in a number of discrete steps, but that number can be changed, see the documentation.

Here's the code for the examples:

\documentclass{article}
\usepackage{tikz}

\usetikzlibrary{shadows.blur}
\usetikzlibrary{shapes.symbols}

\begin{document}


\begin{center}
  \begin{tikzpicture}
    \node[draw=none,shade,
      top color=blue!40,
      bottom color=blue!5,
      rounded corners=6pt,
      blur shadow={shadow blur steps=5}
    ] {\sffamily\bfseries\large A pretty box};

    \node[tape,draw=none,shade,
      top color=blue!40,
      bottom color=blue!5,
      rounded corners=1pt,
      blur shadow={shadow blur steps=5,shadow blur extra rounding=1.3pt}
    ] at (5,0){\sffamily\bfseries\large Another pretty box};
  \end{tikzpicture}
\end{center}

\end{document}

Edit

Sometimes, PDF renderers will show a dark line in the center of the shadow. This is due to the way they handle anti-aliasing and clipping. To avoid this:

Use pgf-blur v1.01, which tries hard to hide this artefact
In Acrobat, turn off the "Page Display" preference "Enhance thin lines". These shadows consist of many thin lines, and they won't look good if Acrobat changes their width
Don't use too many blur shadow steps. It looks best if you have about two pixels per step at viewing resolution.

[Tex/LaTex] Why does PGF/TikZ 3.0 draw the simple layered graph as non-planar by default

Based on percusse's answer you can change the number of minimum layers (e.g. the minimum number of levels that an edge must span) only for the edge from C to F:

\documentclass[tikz,margin=5mm]{standalone}
\usetikzlibrary{graphs, graphdrawing}
\usegdlibrary{layered}

\begin{document}
\tikz [gr/.style={gray!50}, font=\bfseries]
\graph [layered layout] {
    A -- C -- F [>minimum layers=2],
    { [nodes=gr, edges=gr] A -- B -- { E, D -- F } },
};
\end{document}

enter image description here

In addition you can set the weight parameter of the edge from D to F to 0:

\documentclass[tikz,margin=5mm]{standalone}
\usetikzlibrary{graphs, graphdrawing}
\usegdlibrary{layered}

\begin{document}
\tikz [gr/.style={gray!50}, font=\bfseries]
\graph [layered layout] {
    A -- C -- F [>minimum layers=2],
    { [nodes=gr, edges=gr] A -- B -- { E, D -- F [>weight=0] } },
};
\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Faded drop-shadow using tikz-based rounded rectangle

[Tex/LaTex] Why does PGF/TikZ 3.0 draw the simple layered graph as non-planar by default

Related Question