如何在 Tikz 中使用花括号创建注释

Question

大家好，我想创建这个图像的图形：

我可以创建它，但我不知道如何添加箭头、注释和花括号。

这是我的 MWE：

\documentclass{standalone}
\usepackage{tikz}
\begin{document}
    \begin{tikzpicture}
        %coordinate system
        \draw[->] (0,0,0)--++(14,0,0) node[right]{$x$};
        \draw[->] (0,0,0)--++(0,5,0) node[above]{$y$};
        \draw[->] (0,0,0)--++(0,0,10) node[below left]{$z$};
        
        % rectangle 1
        \draw[thick, preaction={fill=blue}] 
        (8.5,0,6) node[anchor=north]{$$}
        -- (8.5,3.6,6) node[anchor=north]{$$}
        -- (3.5,3.8,0.1) node[anchor=south]{$$}
        -- (3,0,-0.81) node[anchor=south]{$$}
        -- cycle;
        
        % rectangle 2
        \draw[thick, preaction={fill=blue}] 
        (8.5,0,6) node[anchor=north]{$$}
        -- (8.5,3.6,6) node[anchor=north]{$$}
        -- (8.9,3.5,6) node[anchor=south]{$$}
        -- (8.9,0,6) node[anchor=south]{$$}
        -- cycle;
        
        % rectangle 3
        \draw[thick, preaction={fill=blue}] 
        (8.9,3.5,6) node[anchor=north]{$$}
        -- (8.5,3.5,6) node[anchor=north]{$$}
        -- (3.8,3.83,0.45) node[anchor=south]{$$}
        -- (3.9,3.5,-0.1) node[anchor=south]{$$}
        -- cycle;
        
        % the connections
        \draw[ultra thick](1,0,-1)--(1,4,-1);
        \draw[ultra thick](1,0,-1)--(6,0,6);
        \draw[ultra thick](6,0,6)--(12,0,6);
        \draw[ultra thick](6,0,6)--(6,4,6);
        \draw[ultra thick](1,4,-1)--(6,4,6);
        
        \draw[ultra thick](12,0,6) arc (0:90:5.9 and 4);% one quarter circle 1
        \draw[ultra thick](12,0,6) arc (0:70:12.5 and 7);% one quarter circle 2
        % colored one quarter circle 3
        \draw[ultra thick, preaction={fill=blue,very nearly transparent}]
        (12,0,6) arc (10:90:8.3 and 3.2);% one quarter circle 4
        
        
        
        % triangle
        \draw[transparent, preaction={fill=blue,very nearly transparent}] (12,0,6) node[anchor=north]{$$}
        -- (6,0,6) node[anchor=north]{$$}
        -- (1,0,-1) node[anchor=south]{$$}
        -- cycle;
    \end{tikzpicture}
\end{document}

Answer 1

所以，已经过去将近一天了，却没有答复。

我编写的代码非常静态，不易修改。我使用了 3 个库：

1. calc计算一些坐标位置。
2. intersections计算蓝色矩形与其他形状相交的位置。
3. decorations.pathreplacing绘制括号。

我相信还有很大的进步空间。

结果

代码

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{intersections}
\usetikzlibrary{decorations.pathreplacing}

\begin{document}
\begin{tikzpicture}
%coordinate system
%   \draw[->] (0,0,0)--++(14,0,0) node[right]{$x$};
%   \draw[->] (0,0,0)--++(0,5,0) node[above]{$y$};
%   \draw[->] (0,0,0)--++(0,0,10) node[below left]{$z$};
%   
% Define the base points
\coordinate (a) at (0,0) ;
\coordinate (b) at (0:5) ;
\coordinate (c) at (130:2.5);

\coordinate (d) at (0,3) ;
\coordinate (e) at ($(b) + (0,3)$);
\coordinate (f) at ($(c) + (0,3)$);

%
\draw [name path = p2](b) .. controls (1,2) ..(c);
\draw (f) -- (c) -- (a) -- (b);
\draw (a) --(d)--(f);
\draw [name path= p3](b) .. controls  (2,3) .. (d);
\draw [name path= p4](b) .. controls  (2,3.5) .. (f);


% defining the blue retangle
\coordinate (m1) at ($(a)!0.5!(b)$);
\path [name path= pm1] (m1) --($(m1)+(130:2.5)$);
\path [name path= pm2] (m1) --($(m1)+(0,5)$);
*
\path [name intersections = {of = p2 and pm1, by = m2}];
\path [name intersections = {of = p3 and pm2, by = m3}];
%
\path [name path= pm3] (m2) --($(m2)+(0,5)$);
\path [name intersections = {of = p4 and pm3, by = m4}];
%
\draw (m4)--(m3)--(m1) -- (m2)--cycle;

% make the blue rectangle 3D by creating a quasi-copy just next ot it.
\coordinate (c1) at ($(m1)-(0.5,0)$);
\path [name path= cm1] (c1) --($(c1)+(130:2.5)$);
\path [name path= cm2] (c1) --($(c1)+(0,5)$);

\path [name intersections = {of = p2 and cm1, by = c2}];
\path [name intersections = {of = p3 and cm2, by = c3}];
%
\path [name path= cm3] (c2) --($(c2)+(0,5)$);
\path [name intersections = {of = p4 and cm3, by = c4}];
%
\draw (c4)--(c3)--(c1) -- (c2)--cycle;

\fill [blue, opacity=0.5](c1) -- (m1)-- (m3)--(m4) --(c4)  -- (c2) -- cycle;

% put the braces
\draw [decorate,decoration={brace,amplitude=10pt,aspect=0.65}]  (c1)--(c2) ;
\draw [decorate,decoration={brace,amplitude=10pt}]  (m1)--(a);

% now annotate :
\node[below left of=a] (eq)  {$1 -\frac{x^2}{4}$};
\draw (eq) -- ($(c1)!0.5!(c2)- (0.6,0)$);

% showing the thickness of blue
\coordinate (c4bis) at ($(c4) + (0,2)$);
\coordinate (m4bis) at ($(c4) + (0,2) +(0.6,0)$);
\draw (c4) --(c4bis);
\draw (m4) --(m4bis);

\node at ($(c4bis)!0.5! (m4bis)$) {$\Delta x$};

\end{tikzpicture}
\end{document}