如何在 TikZ 中绘制一排带有一些额外边的不完整半圆的图形

Question

我想画一些类似于我附上的手绘图片（第二张图片）的东西。这实际上是图 2 的线有向图的一部分（具有指定的方向），我也附上了。我意识到我需要使用几个 for-each 循环，但我不确定如何在 for-each 循环中绘制有向边。很抱歉我没有附上任何代码，但我甚至不知道如何开始。

先感谢您。

Answer 1

您可以利用\pics 然后轻松放置和连接它们。

扩展 MS-SPO 的精彩答案：

\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\tikzset{
    pics/incomplete semicircle/.style={
        code={
            \tikzset{
                incomplete semicircle/.cd, 
                #1,
                arrow decoration outer/.style={
                    decoration={
                        markings,
                        mark={at position 0.08 with {\arrow{stealth}}},
                        mark={at position 0.20 with {\arrow{stealth}}},
                        mark={at position 0.32 with {\arrow{stealth}}},
                        mark={at position 0.44 with {\arrow{stealth}}},
                        mark={at position 0.57 with {\arrow{stealth}}},
                        mark={at position 0.76 with {\arrow{stealth}}},
                        mark={at position 0.95 with {\arrow{stealth}}}
                    },
                    postaction={decorate}
                },
                arrow decoration inner/.style={
                    decoration={
                        markings,
                        mark={at position 0.3 with {\arrow{stealth}}},
                        mark={at position 0.8 with {\arrow{stealth}}}
                    },
                    postaction={decorate}
                }
            }
            \coordinate (-A) at (150:1);
            \coordinate (-B) at (120:1);
            \coordinate (-C) at (90:1);
            \coordinate (-D) at (60:1);
            \coordinate (-E) at (30:1);
            \coordinate (-F) at (0:.5);
            \coordinate (-G) at (90:.5);
            \coordinate (-H) at (0:-.5);
            \draw[incomplete semicircle/arrow decoration outer] 
                (-A) arc[start angle=150, end angle=30, radius=1] --
                (-F) -- (-H) -- cycle;
            \draw[incomplete semicircle/arrow decoration inner] 
                (-H) -- (-G) -- (-F);
            \foreach \p in {A,B,...,H}{
                \node[circle, draw, fill=white, inner sep=0.75pt] 
                    (-n\p) at (-\p) {};
            }
        }
    },
    arrowed/.style={
        decoration={
            markings,
            mark={at position 0.55 with {\arrow{stealth}}}
        },
        postaction={decorate}
    }
}

\begin{document}

 \begin{tikzpicture}
    \pic (c1) at (0,0) {incomplete semicircle};
    \pic (c2) at (2,0) {incomplete semicircle};
    \draw[arrowed] (c1-nF) -- (c2-nH);
    \draw[arrowed] (c2-nA) -- (c1-nF);
 \end{tikzpicture}

\end{document}

Answer 2

以下是一些开始的内容。主要步骤：

• 忽略postaction，绘制“半圆”和实心圆很容易
• 使用起来polar coorinates很容易，记住 3 个coordinateA、B 和 C
• arc移动到起始位置后需要 3 个参数： (startAngle:endAngle:radius )
• decorations.markings最后使用lib添加装饰
• 对定位进行一些微调

当然，一些代码部分可以进一步重构为一些foreach循环。

不幸的是，我没能成功将整个绘图移到 中\pic。一旦成功，就很容易了：

• 把其中 5 个排成一行
• 从内部访问坐标\pic或明确指定它们
• 绘制缺失的几个连接器

\documentclass[10pt,border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\begin{document}

 \begin{tikzpicture}
    [decoration={
        markings,
        mark=between positions 0.06 and 1 step 5.3mm with {\arrow{stealth}} 
    }]
    % ~~~ "semicircle" ~~~~~~~~~~
    \draw [postaction={decorate}] (150:1) arc(150:30:1) -- (0:.5) coordinate (B) -- (0:-.5)  coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) -- (B) ;
    
    % ~~~ filled circles ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    \draw [fill=white] (150:1) circle [radius=1pt];
    \draw [fill=white] (120:1) circle [radius=1pt];
    \draw [fill=white] (90:1) circle [radius=1pt];
    \draw [fill=white] (60:1) circle [radius=1pt];
    \draw [fill=white] (30:1) circle [radius=1pt];
    
    \draw [fill=white] (A) circle [radius=1pt];
    \draw [fill=white] (B) circle [radius=1pt];
    \draw [fill=white] (C) circle [radius=1pt];
 \end{tikzpicture}

\end{document}

最后，这里是重构实心圆位置的代码：

\documentclass[10pt,border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\begin{document}

 \begin{tikzpicture}
    [decoration={
        markings,
        mark=between positions 0.06 and 1 step 5.3mm with {\arrow{stealth}} 
    }]
    % ~~~ "semicircle" ~~~~~~~~~~
    \draw [postaction={decorate}] (150:1) arc(150:30:1) -- (0:.5) coordinate (B) -- (0:-.5)  coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) -- (B) ;
    
    % ~~~ filled circles ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    %     refactored
    \foreach \p in {(150:1),(120:1),(90:1),(60:1),(30:1),(A),(B),(C)}{
        \draw [fill=white] \p circle [radius=1pt];
    }
 \end{tikzpicture}

\end{document}

正如贾斯珀（Jasper）评论的那样，半圆的路径至少应该在这里分开：

... coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) ...

我继续画最后 3 个点，纯粹是为了偷懒。定义第二种装饰风格，以便更好地放置箭头，这也是一种选择。提前一个点开始“半圆”也可能是一个不错的选择，即在弧线之前，即在左下角。可能会产生一些有益的结果。

---

事实证明，你也可以分割装饰风格；左下角的点很关键，因为有两条路径穿过它：

\documentclass[10pt,border=3mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\begin{document}

 \begin{tikzpicture}
    [decoration={
        markings,
        mark=between positions 0.06 and .5 step 5.3mm with {\arrow{stealth}} ,
        mark=between positions 0.6 and .8 step 6mm with {\arrow{stealth}} ,% new
        mark=between positions 0.835 and 1 step 6mm with {\arrow{stealth}}% new
    }]
    % ~~~ "semicircle" ~~~~~~~~~~
    \draw [postaction={decorate}] (150:1) arc(150:30:1) -- (0:.5) coordinate (B) -- (0:-.5)  coordinate (A) -- (150:1) (A) -- (90:.5) coordinate (C) -- (B) ;
    
    % ~~~ filled circles ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    %     refactored
    \foreach \p in {(150:1),(120:1),(90:1),(60:1),(30:1),(A),(B),(C)}{
        \draw [fill=white] \p circle [radius=1pt];
    }
 \end{tikzpicture}

\end{document}