如何调整TikZ中L形箭头的起始位置以避免图形重叠

问题描述 #

需要调整图表中从“Regimes (of sovereign states)”框引出的L形箭头位置，让箭头从该框的y轴更低位置出发，避免与“Non-regimes”框产生干扰。可复现代码如下：

\documentclass[12pt]{article}
\usepackage[margin=1in]{geometry}
\usepackage{graphicx}
\usepackage{pdflscape}
\usepackage{palatino}
\usepackage[table,xcdraw]{xcolor}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric, arrows, positioning}

\tikzstyle{arrow}=[draw, -latex]
\tikzstyle{tblock} = [rectangle, rounded corners, minimum width=4cm, minimum height=3cm,text centered, draw=black, fill=white]
\tikzstyle{autoblock} = [rectangle, rounded corners, minimum width=4cm, minimum height=3cm,text centered, draw=black, fill=gray!20]

\begin{figure}[H]
\caption{Concept Ladder of Regime Types: Residual vs. Substantive Authoritarianism\\}
\vspace*{10mm}
\centering
\begin{tikzpicture}
\node (state) [tblock, text width=3cm] {States of the world};
\node (reg) [tblock, below left= 1cm and .25cm of state, text width=3cm] {Regimes \\ (of sovereign states)};
\node (nonreg) [autoblock, below right= 1cm and .25cm of state, text width=3cm] {Non-regimes \\ (anarchy, foreign \\ occupation, transition)};
\draw [arrow] (state) -- (reg);
\draw [arrow] (state) -- (nonreg);
\node (demone) [tblock, below left=2cm and .25cm of reg, text width=3cm] {Democratic regimes};
\draw [arrow] (reg) -| (demone);
\node (auto) [autoblock, below right=2cm and 4.5cm of reg, text width=3cm] {Authoritarian regimes \\ (substantive authoritarianism)};
\draw [arrow] (reg) -| (auto);
\node (lfs) [autoblock, below = 2cm of reg, text width=3cm] {Limited franchise \\ systems};
\draw [arrow] (reg) -- (lfs);
\node (dfr) [autoblock, below right=2cm and .25cm of reg, text width=3cm] {Dominant faction \\ regimes};
\draw [arrow] (reg) -| (dfr);

\end{tikzpicture}
\end{figure}

\end{document}

解决方案 #

核心思路是指定箭头从“Regimes”框的底部节点（而非默认的中心节点）出发，TikZ中可以通过节点的*锚点（anchor）*来精准控制起始位置：

• 对于从reg框引出的L形箭头，将原来的(reg)替换为(reg.south)（框的底部中心），或者根据需要选择(reg.south east)（右下角）、(reg.south west)（左下角）等锚点，这样箭头会从框的下部开始，避开上方的“Non-regimes”框。
• 如果需要更精细的调整，可以在锚点基础上偏移坐标，比如(reg.south) + (0, -0.2cm)，让箭头起点再往下一点，进一步避免干扰。

修改后的完整代码如下：

\documentclass[12pt]{article}
\usepackage[margin=1in]{geometry}
\usepackage{graphicx}
\usepackage{pdflscape}
\usepackage{palatino}
\usepackage[table,xcdraw]{xcolor}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric, arrows, positioning}

\tikzstyle{arrow}=[draw, -latex]
\tikzstyle{tblock} = [rectangle, rounded corners, minimum width=4cm, minimum height=3cm,text centered, draw=black, fill=white]
\tikzstyle{autoblock} = [rectangle, rounded corners, minimum width=4cm, minimum height=3cm,text centered, draw=black, fill=gray!20]

\begin{figure}[H]
\caption{Concept Ladder of Regime Types: Residual vs. Substantive Authoritarianism\\}
\vspace*{10mm}
\centering
\begin{tikzpicture}
\node (state) [tblock, text width=3cm] {States of the world};
\node (reg) [tblock, below left= 1cm and .25cm of state, text width=3cm] {Regimes \\ (of sovereign states)};
\node (nonreg) [autoblock, below right= 1cm and .25cm of state, text width=3cm] {Non-regimes \\ (anarchy, foreign \\ occupation, transition)};
\draw [arrow] (state) -- (reg);
\draw [arrow] (state) -- (nonreg);
\node (demone) [tblock, below left=2cm and .25cm of reg, text width=3cm] {Democratic regimes};
% 修改箭头起点为reg左下角
\draw [arrow] (reg.south west) -| (demone);
\node (auto) [autoblock, below right=2cm and 4.5cm of reg, text width=3cm] {Authoritarian regimes \\ (substantive authoritarianism)};
% 修改箭头起点为reg右下角
\draw [arrow] (reg.south east) -| (auto);
\node (lfs) [autoblock, below = 2cm of reg, text width=3cm] {Limited franchise \\ systems};
\draw [arrow] (reg) -- (lfs);
\node (dfr) [autoblock, below right=2cm and .25cm of reg, text width=3cm] {Dominant faction \\ regimes};
% 修改箭头起点为reg底部中心
\draw [arrow] (reg.south) -| (dfr);

\end{tikzpicture}
\end{figure}

\end{document}

调整后，所有从reg框引出的L形箭头都会从框的下部出发，完全避开“Non-regimes”框的干扰，满足需求。

内容的提问来源于stack exchange，提问作者Ashley Anderson