What's the most practical way to draw such a thing?

Question

I'm just trying to learn graphical packages (tikz, pgfplots..) and I would like to see how a more expert user would approach such a drawing.

Answer 1

You need to know around 5 things about TikZ.
Then somehow like this:

\documentclass[margin=5pt, tikz]{standalone}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{backgrounds}
\usetikzlibrary{angles, quotes, babel}
\usetikzlibrary {arrows.meta, bending}
\usetikzlibrary{decorations.markings}

\definecolor{mybgcolor}{HTML}{F8F6E9}

\begin{document}
\pgfmathsetmacro\wTheta{22.5}
\pgfmathsetmacro\L{2.575}
\begin{tikzpicture}[font=\footnotesize, 
>={Triangle[length=0pt 3*2.5,width=0pt 2.5]},
background rectangle/.style={draw=none, fill=mybgcolor}, 
show background rectangle,
]

% 1
\draw[step=0.5, help lines] (-0.2,-0.2) grid (4.2,3.2);

% 2
\draw[red, thick] (1,0.5) coordinate(A1) -- +(\wTheta:\L) coordinate(B1) ;
\draw[red, thick] (1,2) coordinate(A2)  -- +(\wTheta:\L) coordinate(B2) ;

% 3
\draw[red, densely dotted] (A2) -- ($(A1)!(A2)!(B1)$) coordinate(A2s) coordinate[pos=1.35, label=center:](A2ss);

\draw[densely dotted] (A2s) -- (A2ss); 

\draw[densely dotted, shorten >=-1mm] (A1) -- ($(A1)!2.25mm!-90:(B1)$) coordinate(A1s);

\draw[<->] (A1s) -- ($(A2s)!(A1s)!(A2ss)$) node[midway, below, sloped, inner sep=1.5pt]{$\Delta$}; 


% 4
\draw[<->] ([xshift=-6mm]A1) -- ([xshift=-6mm]A2) node[midway, right]{$d$};

% 5a
\tikzset{
pics/mypic/.style={%%
code={
\node[rectangle, draw=none, inner sep=0pt, 
minimum width=1mm, minimum height=10mm, 
rotate=#1,
](s){};
%
\draw[rotate=#1] ([yshift=1mm]s.west)
    -- ([yshift=1mm]s.east) coordinate[label=](P2)
        -- (s.north east) coordinate[label=](Q2); 
\draw[rotate=#1] ([yshift=-1mm]s.west) 
   -- ([yshift=-1mm]s.east)  coordinate[label=](P1)
      -- (s.south east) coordinate[label=](Q1); 
}},%%
}

% 5b
\path[] ([xshift=-0.5mm]A1) pic{mypic={0}};

\draw pic [draw, angle radius=4mm, angle eccentricity=1.35,
"$\theta$", green!66!black, <-,
] {angle =A2s--A1--Q2};

\begin{scope}[decoration={
markings, 
mark=at position 0.75 with {\arrow[red]{>}}}]
\path[draw=none, postaction=decorate] (P2) -- (Q2);
\end{scope}

% 5c
\path[] ([yshift=-0.5mm]A2) pic{mypic={90}};

\draw pic [draw, angle radius=4mm, angle eccentricity=1.75,
"$\theta'$", blue, <-,
] {angle =Q1--A2--B2};

\begin{scope}[decoration={
markings, 
mark=at position 0.6 with {\arrow[red]{>}}}]
\path[draw=none, postaction=decorate] (P1) -- (Q1);
\end{scope}

% 6
\draw pic [draw, angle radius=1mm] {right angle =A2--A2s--A1};
\end{tikzpicture}
\end{document}