如何使用具有明确定位的 TikZ 树节点的叉式边？

Question

作为图形导出功能的一部分，我尝试在 TikZ 中渲染一棵树，其中所有节点位置都准确给出并且边是叉形的。

在没有树木包要求我根据给定的节点坐标自己计算边缘“角”，这是我想避免的。

向 TikZ 树添加明确定位的节点会弄乱布局，因为（根据手册），TikZ 正在更改每个子节点的坐标系。

没有树木：

\documentclass{article}
\usepackage{tikz}
\begin{document}

\begin{figure}
\begin{tikzpicture}
\node at (10, 10) (root) {root} ;
\node at (10, 7) (lvl1middle) {lvl1middle} ;
\node at (8, 6) (lvl2left) {lvl2left} ;
\node at (13, 5) (lvl2right) {lvl2right} ;
\node at (10, 5) (lvl2middle) {lvl2middle} ;
\draw (root) -- (lvl1middle);
\draw (lvl1middle) -- (lvl2left);
\draw (lvl1middle) -- (lvl2middle);
\draw (lvl1middle) -- (lvl2right);
\end{tikzpicture}
\end{figure}
\end{document}

有樹：

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{trees} 
\begin{document}

\begin{figure}
\begin{tikzpicture}
\node at (10, 10) (root) {root}
    [edge from parent fork down]
    child { node at (10, 7) (lvl1middle) {lvl1middle} 
        child { node at (8, 6) (lvl2left) {lvl2left} }
        child { node at (13, 5) (lvl2right) {lvl2right} }
        child { node at (10, 5) (lvl2middle) {lvl2middle} }
    }; 
\end{tikzpicture}
\end{figure}
\end{document}

Answer 1

只是安装了一个我们可以用于的edge from parent fork down特殊函数。原始定义是edge from parent pathto path

\tikzset{edge from parent fork down/.style={
  edge from parent path={(\tikzparentnode\tikzparentanchor) -- +(0pt,-.5\tikzleveldistance) 
                                                      -| (\tikzchildnode\tikzchildanchor)}}}

默认\tikzleveldistance值为15mm。

一个解决方案to path是

\tikzset{
  edge down and up again/.style={
    to path={
       |- ([shift={(\tikztotarget.south)}] +0pt,+-2.5mm) -- (\tikztotarget) }}}

在您的示例中，我必须切换回默认路径line to（即--），因为边缘必须以这种方式绕过目标节点。

代码

\documentclass[tikz,convert=false]{standalone}
\tikzset{
  edge down and up again/.style={
    to path={
       |- ([shift={(\tikztotarget.south)}] +0pt,+-2.5mm) -- (\tikztotarget) }}}
\begin{document}
\begin{tikzpicture}
\node at (10, 10) (root) {root} ;
\node at (10, 7) (lvl1middle) {lvl1middle} ;
\node at (8, 6) (lvl2left) {lvl2left} ;
\node at (13, 5) (lvl2right) {lvl2right} ;
\node at (10, 5) (lvl2middle) {lvl2middle} ;

\path[edge down and up again] (root) edge [line to] (lvl1middle)
                        (lvl1middle) edge           (lvl2left)
                                     edge [line to] (lvl2middle)
                        (lvl2middle) edge           (lvl2right);
\end{tikzpicture}
\end{document}

输出