为什么连接一列中的节点和另一列中的另一个节点的曲线会消失？

Question

我想显示项目，每个项目都有一条指向右图上某个点的曲线。但在以下代码中，曲线消失了。哪里出了问题？

\documentclass{beamer}
\usepackage{graphicx}
\usepackage{pst-node}

\newsavebox\IBox
\savebox\IBox{\includegraphics[scale=.5]{example-image-a}}

\psset{xunit=.1\wd\IBox,yunit=.1\ht\IBox,arrows=->,linecolor=red}

\begin{document}
\begin{frame}[t]{Hello World and Hello Universe}
\begin{columns}[t]
    \begin{column}{.3\linewidth}
    \begin{enumerate}
        \item<2-> \rnode[r]{HWl}{Hello World}\nccurve{HWl}{HWr}
        \item<3-> \rnode[r]{HUl}{Hello Universe}\nccurve{HUl}{HUr}
    \end{enumerate}
    \end{column}
    \begin{column}{.7\linewidth}
    \begin{center}
        \begin{pspicture}[showgrid=top](10,10)
        \rput[bl](0,0){\usebox\IBox}
        \pnode(2,4){HWr}
        \pnode(5,8){HUr}
        \end{pspicture}
    \end{center}
    \end{column}
\end{columns}
\end{frame}
\end{document}

Answer 1

节点HWr和HUr仅在您命令后定义\nccurve。您可以添加例如

\only<2>{\nccurve{HWl}{HWr}}
\only<3>{\nccurve{HUl}{HUr}}

定义所有节点后：

\documentclass{beamer}
\usepackage{graphicx}
\usepackage{pst-node}

\newsavebox\IBox
\savebox\IBox{\includegraphics[scale=.5]{example-image-a}}

\psset{xunit=.1\wd\IBox,yunit=.1\ht\IBox,arrows=->,linecolor=red}

\begin{document}
\begin{frame}[t]{Hello World and Hello Universe}
\begin{columns}[t]
    \begin{column}{.3\linewidth}
    \begin{enumerate}
        \item<2-> \rnode[r]{HWl}{Hello World}\nccurve{HWl}{HWr}
        \item<3-> \rnode[r]{HUl}{Hello Universe}\nccurve{HUl}{HUr}
    \end{enumerate}
    \end{column}
    \begin{column}{.7\linewidth}
    \begin{center}
        \begin{pspicture}[showgrid=top](10,10)
        \rput[bl](0,0){\usebox\IBox}
        \pnode(2,4){HWr}
        \pnode(5,8){HUr}
        \only<2>{\nccurve{HWl}{HWr}}
        \only<3>{\nccurve{HUl}{HUr}}
        \end{pspicture}
    \end{center}
    \end{column}
\end{columns}
\end{frame}
\end{document}