path 的选项 in、out、relative、looseness 之间有什么关系？

Question

下面的例子，

\documentclass{article}
\usepackage{booktabs}
\usepackage{tikz}
\usetikzlibrary{tikzmark}
\begin{document}
\begin{tabular}{ll}
\tikzmarknode{FooUp}{foo} & foo\\
foo & foo\\
foo & foo\\
\tikzmarknode{FooDown}{foo} & foo\\[1em]
bar & \tikzmarknode{BarUp}{bar}\\
bar & bar\\
bar & bar\\
bar & \tikzmarknode{BarDown}{bar}\\
\end{tabular}
\begin{tikzpicture}[remember picture, overlay, very thin]
  \draw (FooUp.north west)
    -- (FooDown.south west)
    to[out=-90, in=90, looseness=1] (BarUp.north west)
    -- (BarDown.south west);
  \draw (FooUp.north east)
    -- (FooDown.south east)
    to[out=-90, in=90, relative, looseness=1] (BarUp.north east)
    -- (BarDown.south east);
  \draw (FooDown.south east)
    to[out=-90, in=90, relative, looseness=2] (BarUp.north east);
  \draw (FooDown.south east)
    to[out=-90, in=90, relative, looseness=0.5] (BarUp.north east);
\end{tikzpicture}
\end{document}

生成此输出

我知道使用角度是相对于水平线的。out=-90, in=90, relative

但是，我不明白 生成的角度out=-90, in=90, relative相对于 是什么。无论 ，它们似乎都相同looseness，那么仅凭起点和终点的坐标如何能确定in和out角度？