控制点坐标

Question

我的问题是，当我想画一条曲线时，我不知道控制点应该放在哪里。有没有计算坐标的方法？例如，我想在这里画这条曲线，但我不知道控制点在哪里。我可以猜测，但那并不准确。

感谢您的帮助！

Answer 1

因为这是一条曲线。您可以选择三个点并将它们连接起来。

(A) to [out=angle1,in=angle2] (B);

其中 A 和 B 是点，而 angle1 和 angle2 控制曲线进入和离开点的方式。

这是代码

\documentclass[border={10}]{standalone}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
\coordinate (A)  at (0,0);
\coordinate (B)  at (0,-1);
\coordinate (C)  at (1,0);

\draw[very thick] (A) to [out=225,in=180,looseness=1.5] (B);
\draw[very thick] (B) to [out=0,in=270]               (C);

\end{tikzpicture}

\end{document}

---

编辑：关于和in，out我将向您展示曲线离开 A 点的方式，其余部分将一目了然。关于looseness，它使线条更加弯曲。尝试更改它以查看其效果。

选修的： 这是上面图片的代码

\documentclass[border={10}]{standalone}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
[%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
        Circ/.style={circle,fill=blue,thick,
                      inner sep=0pt,minimum size=1mm}
]%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\coordinate (A)  at (0,0);
\coordinate (B)  at (0,-1);
\coordinate (C)  at (1,0);

\draw[very thick] (A) to [out=225,in=180,looseness=1.5] (B);
\draw[very thick] (B) to [out=0,in=270]                 (C);


\draw[red] (-.8,0) -- (1.5,0);
\draw[red] ( 0,.5) -- (0,-1.3);

\node [Circ,label={[xshift=-5mm]30:A}]             at (A) {};
\node [Circ,label={[xshift=-5mm,yshift=-5mm]30:B}] at (B) {};
\node [Circ,label={[xshift=-5mm]30:C}]             at (C) {};

\draw [green] (.1,0) arc (0:225:.1) node[xshift=-2.5mm,yshift=.15mm] {\tiny out} ;

\end{tikzpicture}

\end{document}

Answer 2

您可以使用..controls (coordinate) and (coordinate) ..语法来绘制贝塞尔曲线。

\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
  \coordinate (A) at (.35,.75);
  \coordinate (B) at (.85,.75);
  \coordinate (C1) at (-.4,.1);
  \coordinate (C2) at (.86,.12);
  \draw[red] (A) .. controls (C1) and (C2) .. (B);
  \node[red,draw,fill,inner sep=1pt] at (A) {};
  \node[red,draw,fill,inner sep=1pt] at (B) {};
\end{tikzpicture}
\end{document}

我把你的图像放在背景中以强调类比。