多条有角度的线汇聚而不是平行（tikz）

Question

我正在尝试绘制一个简单的图表，其中有角度的网格与平面相交。我有两个问题；

\begin{tikzpicture}
        \filldraw[fill = blue!50!white, draw = black]
            (2.2,-0.2) -- (3.8,-0.2) -- (3.8, 0.2) -- (2.2, 0.2) -- cycle;  %Plane surface, centred on (3,0)
        \draw[<-,  line width = 1.6] (3,0) -- (140:3);                      %Incident wave vector
        \foreach \y in {1, 2, 3, 4}
            \draw[dotted] (3, 0.5*\y) -- (140:3);
        \draw[->, line width = 1.6] (3,0) -- (3,2);                     %Normal-to-surface vector
\end{tikzpicture}

首先，该代码产生的是汇聚线而不是平行线（尽管指定了 140 度）我做错了什么？

其次，我该如何添加垂直指向但源自第一个 \draw 命令中定义的轴的线？

Answer 1

这些线不平行，因为你将它们绘制为(140:3)而不是++(<angle>:3)。可以使用 绘制正交线calc。

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
        \filldraw[fill = blue!50!white, draw = black]
            (2.2,-0.2) -- (3.8,-0.2) -- (3.8, 0.2) -- (2.2, 0.2) -- cycle;  %Plane surface, centred on (3,0)
        \draw[<-,  line width = 1.6] (3,0) coordinate (X)-- (140:3)
         foreach \X [count=\Y] in {0.4,0.6,0.8,1} {coordinate[pos=\X] (p\Y)};                     %Incident wave vector
        \foreach \Y in {1,...,4} 
        {\draw[dotted] (p\Y)  -- ($ (p\Y)!2cm!90:(X) $);}
        \draw[dotted] let \p1=($(140:3)-(3,0)$),\n1={atan2(\y1,\x1)}
        in foreach \y in {1, 2, 3, 4} {(3, 0.5*\y) -- ++(\n1:6)};
        \draw[->, line width = 1.6] (3,0) -- (3,2);                     %Normal-to-surface vector
\end{tikzpicture}
\end{document}

Max 善意地指出你可能想要一些不同的东西：

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
        \filldraw[fill = blue!50!white, draw = black]
            (2.2,-0.2) -- (3.8,-0.2) -- (3.8, 0.2) -- (2.2, 0.2) -- cycle;  %Plane surface, centred on (3,0)
        \draw[<-,  line width = 1.6] (3,0) coordinate (X)-- (140:3)
         foreach \X [count=\Y] in {0.2,0.4,0.6,0.8,1} {coordinate[pos=\X] (p\Y)};                     %Incident wave vector
        \foreach \Y in {1,...,5} 
        {\draw[dotted] (p\Y)  -- ++ (0,2.5);}

        \draw[dotted] let \p1=($(140:3)-(3,0)$),\n1={atan2(\y1,\x1)}
        in foreach \y in {1, 2, 3, 4} {(3, 0.5*\y) -- ++(\n1:6)};
        \draw[->, line width = 1.6] (3,0) -- (3,2);                     %Normal-to-surface vector
\end{tikzpicture}
\end{document}