Mindmap circle connection bar drawing

Question

I have the MWE:

\documentclass[border=0pt,tikz]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{mindmap,backgrounds}

%\tikzset{concept/.append style={fill={none}}}

\begin{document}
    \begin{tikzpicture}[
    outer sep=0pt, small mindmap,
    concept color=pink,
    every node/.style={concept}, 
    root/.style    = {concept color=pink,
    }, 
    ]
    \node[root,  anchor=center, minimum size=2.2cm, text width=2.2cm ] {A}
    [clockwise from=120] 

    child[concept color=blue!50,]{
        node[concept] (d) {D} 
        [counterclockwise from=30]
        child { node[concept color=blue!25] (e){E}
            child[counterclockwise from=35] { node[concept color=blue!12.5] (f){F}}
        }
    }
    child[concept color=orange!50] {
        node[concept, ] (h) {H}
        [counterclockwise from=0]
        child { node[concept color = orange!25, sibling angle=120] (i) {I}}
    }
    ;
    %https://tex.stackexchange.com/a/144828/38244
    \path (d) to[circle connection bar switch color=from (blue!50) to (blue!25)] (e);
    \path (e) to[circle connection bar switch color=from (blue!25) to (blue!12.5)] (f);
    \path (h) to[circle connection bar switch color=from (orange!50) to (orange!25)] (i);
    \end{tikzpicture}   
\end{document}

It gives the mindmap:

However, if you look closely, you'll see a drawing on node E, F (highlighted in yellow):

I tried to remove it by setting draw=none to the \path, but it does not work. Anyone knows how to remove these lines?

Answer 1

The main issue is that you do not add the concept color= at the optimal place. If you add it to child instead of node,

\documentclass[border=0pt,tikz]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{mindmap,backgrounds}

%\tikzset{concept/.append style={fill={none}}}

\begin{document}
    \begin{tikzpicture}[
    outer sep=0pt, small mindmap,
    concept color=pink,
    every node/.style={concept}, 
    root/.style    = {concept color=pink,
    }, 
    ]
    \node[root,  anchor=center, minimum size=2.2cm, text width=2.2cm ] {A}
    [clockwise from=120] 

    child[concept color=blue!50,]{
        node[concept] (d) {D} 
        [counterclockwise from=30]
        child[concept color=blue!25] { node (e){E}
            child[counterclockwise from=35,concept color=blue!12.5] { node (f){F}}
        }
    }
    child[concept color=orange!50] {
        node[concept, ] (h) {H}
        [counterclockwise from=0]
        child[concept color = orange!25] { node[sibling angle=120] (i) {I}}
    }
    ;
    %https://tex.stackexchange.com/a/144828/38244
%   \begin{scope}[on background layer]
%     \path (d) to[circle connection bar switch color=from (blue!50) to (blue!25)] (e);
%     \path (e) to[circle connection bar switch color=from (blue!25) to (blue!12.5)] (f);
%     \path (h) to[circle connection bar switch color=from (orange!50) to (orange!25)] (i);
%   \end{scope}
    \end{tikzpicture}   
\end{document}

you get

which is already pretty good. However, if you look very closely, you may see a tiny gap

This gap is not there when viewed with acroread.

If you now reinstall your connections, i.e. activate

\path (e) to[circle connection bar switch color=from (blue!25) to (blue!12.5)] (f);

then this gap is gone when viewed with preview, likewise for the other connections. Under acroread, this gap was not there in the first place.

ADDENDUM: This suggests that these connecting bars are not needed at all, at least if you use acroread to view the mindmap. However, this is not quite true, you will need them to draw additional connections that are not part of the original mindmap hierarchy, e.g.

\draw (h) to[circle connection bar switch color=from (orange!50) to (blue!12.5)] (f);

Under acroread I get a spotless additional connection. Note that I used \draw instead of \path to get a better result.