使用定位库在 tikz 中制作交换图时出现问题

Question

我正在使用定位 TikZ 库制作交换图。我无法让底部箭头处于水平状态。

这是我的问题的输出：定位库在左边，我认为应该得到的输出（用矩阵库完成）在右边。问题是上面的箭头$\psi^{-1}$：它在图表的左侧版本上不是完全水平的。

我做错了什么？为什么我不应该在左侧和右侧获得相同的图片？

这是我的代码：

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{matrix,positioning}


\begin{document}


\[
\begin{tikzpicture}[  baseline=(current bounding box.center)]
  % Tell it where the nodes are
  \node (F) {$M^P \cap \pi_W^{-1}( U) $};
  \node (E) [right=of F] {$V$};
  \draw[->] (F)-- node [above] {\footnotesize $\pi_V$} (E);
   \node (C) [below=of F] {$U \subset W$};
   \draw[->] (F)-- node [left] {\footnotesize $\pi_W$} (C);
  \node (B) [below=of E] {$I \times V$};
  \draw[->] (C)-- node [below] {\footnotesize $\psi^{-1}$} (B);
  \draw[<-] (E)-- (B);
\end{tikzpicture}
=
\begin{tikzpicture}[every node/.style={midway},  baseline=(current bounding box.center)]
\matrix[column sep={6em,between origins},
        row sep={3em}] at (0,0)
{ 
  \node (F) {$M^P \cap \pi_W^{-1}( U) $}; & 
  \node (E) {$V$};\\
     \node (C) {$U \subset W$};&
      \node (B) {$I \times V$};\\};
        \draw[->] (F)-- node [above] {\footnotesize $\pi_V$} (E);
   \draw[->] (F)-- node [left] {\footnotesize $\pi_W$} (C);
  \draw[->] (C)-- node [below] {\footnotesize $\psi^{-1}$} (B);
  \draw[<-] (E)-- (B);
\end{tikzpicture}
\]
\end{document}

Answer 1

这是正常的。第一行的节点高度不同。您需要使用选项on grid

every node/.style={midway}你可以在第二张图片中删除

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{matrix,positioning}

\begin{document}

\begin{tikzpicture}[every node/.style={on grid},  baseline=(current bounding box.center),node distance=2]
  % Tell it where the nodes are
  \node (F) {$M^P \cap \pi_W^{-1}( U) $};
  \node (E) [right=of F] {$V$};
  \draw[->] (F)-- node [above] {\footnotesize $\pi_V$} (E);
   \node (C) [below=of F] {$U \subset W$};
   \draw[->] (F)-- node [left] {\footnotesize $\pi_W$} (C);
  \node (B) [below=of E] {$I \times V$};
  \draw[->] (C)-- node [below] {\footnotesize $\psi^{-1}$} (B);
  \draw[<-] (E)-- (B);
\end{tikzpicture}
=
\begin{tikzpicture}[  baseline=(current bounding box.center)]
\matrix[column sep={6em,between origins},
        row sep={3em}] at (0,0)
{ 
  \node (F) {$M^P \cap \pi_W^{-1}( U) $}; & 
  \node (E) {$V$};\\
     \node (C) {$U \subset W$};&
      \node (B) {$I \times V$};\\};
        \draw[->] (F)-- node [above] {\footnotesize $\pi_V$} (E);
   \draw[->] (F)-- node [left] {\footnotesize $\pi_W$} (C);
  \draw[->] (C)-- node [below] {\footnotesize $\psi^{-1}$} (B);
  \draw[<-] (E)-- (B);
\end{tikzpicture}

\end{document}