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另一个想法。

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另一个想法。

在他的回答到使用 PGF/TikZ 进行圆柱着色，Jake 提供了一个代码来绘制一个顶部没有阴影的阴影圆柱体。

此代码绘制一个圆柱体节点（来自shapes.geometric库），然后使用第二个绘制命令在其上绘制一个椭圆。

我尝试使用选项将两个步骤合并在一起，mycylinder/.style但append after command没有成功。我仍然不完全理解 的作用\pgfinterruptpath，\pgfextra所以可能是我的代码不正确。我想象在对圆柱体进行着色后必须绘制覆盖椭圆，但我不知道该怎么做。你能解释一下哪里出了问题吗？

\documentclass[tikz,border=1mm]{standalone}

\usetikzlibrary{calc,fit,backgrounds,positioning,arrows,shapes.geometric}

\begin{document}

\begin{tikzpicture}[font=\sffamily\small,
   >=stealth',
   mycylinder/.style={
draw,
  shape=cylinder,
  alias=cyl, % Will be used by the ellipse to reference the cylinder
  aspect=1.5,
  minimum height=3cm,
  minimum width=2cm,
  left color=blue!30,
  right color=blue!60,
  middle color=blue!10, % Has to be called after left color and middle color
  outer sep=-0.5\pgflinewidth, % to make sure the ellipse does not draw over the lines
  shape border rotate=90,
  append after command={%
    \pgfextra{%
       \pgfinterruptpath
%          \begin{pgfonlayer}{foreground layer}
          \fill [blue!10] let
             \p1 = ($(\tikzlastnode.before top)!0.5! (\tikzlastnode.after top)$),
             \p2 = (\tikzlastnode.top),
             \p3 = (\tikzlastnode.before top),
             \n1={veclen(\x3-\x1,\y3-\y1)},
             \n2={veclen(\x2-\x1,\y2-\y1)},
             \n3={atan2((\y2-\y1),(\x2-\x1))}
          in 
             (\p1) ellipse [x radius=\n1, y radius = \n2, rotate=\n3];
%          \end{pgfonlayer}
       \endpgfinterruptpath%
    }
  }
 }
]

% Left cylinder. Wrong one.
% I would like to draw right cylinder with only one command.
\path node [mycylinder, label=below:Wrong] (disc) {};

% Right cylinder. Correct one but with two commands.
\path node [mycylinder, right=1cm of disc, label=below:Good] (disc2) {};
\fill [blue!10] let
  \p1 = ($(cyl.before top)!0.5!(cyl.after top)$),
  \p2 = (cyl.top),
  \p3 = (cyl.before top),
  \n1={veclen(\x3-\x1,\y3-\y1)},
  \n2={veclen(\x2-\x1,\y2-\y1)},
  \n3={atan2((\y2-\y1),(\x2-\x1))}
 in 
  (\p1) ellipse [x radius=\n1, y radius = \n2, rotate=\n3];

\end{tikzpicture}
\end{document}

在此处输入图片描述

答案1

TikZ 已经包含了在当前路径中插入单独路径的可能性： 。edge（不幸的是，您不能pgfonlayer在这里使用。但由于参数append after command将在放置节点后执行，所以这应该不是问题。）

由于 CVS 版本将atan2函数的参数交换atan2(x, y)为atan2(y, x)，因此我还在序言中加入了一个小块来理清这个问题并定义函数atanXY和atanYX。

我还选择不改变outer seps，而是直接从半径中减去\pgflinewidth。令人烦恼的是，这些值在节点之后无法访问。

代码

\documentclass[tikz]{standalone}
\usetikzlibrary{calc,shapes.geometric}
\pgfmathparse{atan2(0,1)}
\ifdim\pgfmathresult pt=0pt % atan2(y, x)
  \tikzset{declare function={atanXY(\x,\y)=atan2(\y,\x);atanYX(\y,\x)=atan2(\y,\x);}}
\else                       % atan2(x, y)
  \tikzset{declare function={atanXY(\x,\y)=atan2(\x,\y);atanYX(\y,\x)=atan2(\x,\y);}}
\fi
\begin{document}
\begin{tikzpicture}[font=\sffamily\small,
   mycylinder/.style={draw, shape=cylinder, aspect=1.5, minimum height=+3cm,
    minimum width=+2cm, left color=blue!30, right color=blue!60, middle color=blue!10,
    shape border rotate=90, append after command={%
      let \p{cyl@center} = ($(\tikzlastnode.before top)!0.5! (\tikzlastnode.after top)$),
          \p{cyl@x}      = ($(\tikzlastnode.before top)-(\p{cyl@center})$),
          \p{cyl@y}      = ($(\tikzlastnode.top)       -(\p{cyl@center})$)
      in (\p{cyl@center}) edge[draw=none, fill=blue!10, to path={
        ellipse [x radius=veclen(\p{cyl@x})-1\pgflinewidth,
                 y radius=veclen(\p{cyl@y})-1\pgflinewidth,
                 rotate=atanXY(\p{cyl@x})]}] () }}]
\node[mycylinder, label=below:Better?] {};
\end{tikzpicture}
\end{document}

输出

在此处输入图片描述

另一个想法。

该cylinder形状已经可以选择使用不同的选项填充两个部分

  • cylinder body fill=<color>，
  • cylinder end fill=<color>和开关
  • cylinder uses custom fill。

不幸的是，

cylinder end fill=blue!10,  cylinder uses custom fill,
preaction={draw=red, left color=blue!30, right color=blue!60, middle color=blue!10}

将被绘制在 之上cylinder end fill（在 中完成behindbackgroundpath），即使阴影本身位于 中preaction。

也许可以通过自定义形状来解决这个问题。

键Cylinder end shade和Cylinder body shade实际上是通过\tikzset使用和设置其内容来实现的\tikz@finish（类似于backgroundpath和的foregroundpath应用方式）。

代码

\documentclass[tikz]{standalone}
\usetikzlibrary{shapes.geometric}
\pgfset{
  Cylinder end fill/.initial=,
  Cylinder body fill/.initial=,
  Cylinder end shade/.initial=,
  Cylinder body shade/.initial=}
\makeatletter
\pgfdeclareshape{Cylinder}{%
  \inheritsavedanchors[from=cylinder]%
  \inheritbackgroundpath[from=cylinder]%
  \inheritanchorborder[from=cylinder]%
  \inheritanchor[from=cylinder]{center}\inheritanchor[from=cylinder]{shape center}%
  \inheritanchor[from=cylinder]{mid}\inheritanchor[from=cylinder]{mid east}%
  \inheritanchor[from=cylinder]{mid west}\inheritanchor[from=cylinder]{base}%
  \inheritanchor[from=cylinder]{base east}\inheritanchor[from=cylinder]{base west}%
  \inheritanchor[from=cylinder]{north}\inheritanchor[from=cylinder]{south}%
  \inheritanchor[from=cylinder]{east}\inheritanchor[from=cylinder]{west}%
  \inheritanchor[from=cylinder]{north east}\inheritanchor[from=cylinder]{south west}%
  \inheritanchor[from=cylinder]{south east}\inheritanchor[from=cylinder]{north west}%
  \inheritanchor[from=cylinder]{before top}\inheritanchor[from=cylinder]{top}%
  \inheritanchor[from=cylinder]{after top}\inheritanchor[from=cylinder]{before bottom}%
  \inheritanchor[from=cylinder]{bottom}\inheritanchor[from=cylinder]{after bottom}%
  \behindbackgroundpath{%
    \ifpgfcylinderusescustomfill%
      \getcylinderpoints%
      \pgf@x\xradius\relax%
      \advance\pgf@x-\outersep\relax%
      \edef\xradius{\the\pgf@x}%
      \pgf@y\yradius\relax%
      \advance\pgf@y-\outersep\relax%
      \edef\yradius{\the\pgf@y}%
      {%
        \pgftransformshift{\centerpoint}%
        \pgftransformrotate{\rotate}%
        \pgfpathmoveto{\afterbottom}%
        \pgfpatharc{90}{270}{\xradius and \yradius}%
        \pgfpathlineto{\beforetop\pgf@y-\pgf@y}%
        \pgfpatharc{270}{90}{\xradius and \yradius}%
        \pgfpathclose%
        \edef\pgf@temp{\pgfkeysvalueof{/pgf/Cylinder body fill}}%
        \ifx\pgf@temp\pgfutil@empty
          \edef\pgf@temp{\pgfkeysvalueof{/pgf/Cylinder body shade}}%
          \ifx\pgf@temp\pgfutil@empty
            \pgfusepath{discard}%
          \else % make shading:
            \begingroup
            \expandafter\tikzset\expandafter{\pgf@temp}
            \tikz@finish
          \fi
        \else
          \pgfsetfillcolor{\pgf@temp}%
          \pgfusepath{fill}%
        \fi
        %
        \pgfpathmoveto{\beforetop}%
        \pgfpatharc{90}{-270}{\xradius and \yradius}%
        \pgfpathclose
        \edef\pgf@temp{\pgfkeysvalueof{/pgf/Cylinder end fill}}%
        \ifx\pgf@temp\pgfutil@empty
          \edef\pgf@temp{\pgfkeysvalueof{/pgf/Cylinder end shade}}%
          \ifx\pgf@temp\pgfutil@empty
            \pgfusepath{discard}%
          \else % make shading: 
            \begingroup
            \expandafter\tikzset\expandafter{\pgf@temp}
            \tikz@finish
          \fi
        \else
          \pgfsetfillcolor{\pgf@temp}%
          \pgfusepath{fill}%
        \fi
      }%
    \fi
  }%
}
\makeatother
\begin{document}

\begin{tikzpicture}[font=\sffamily\small, opacity=1,
   mycylinder/.style={shape=Cylinder, aspect=1.5, minimum height=+3cm, draw,
     cylinder uses custom fill, Cylinder end fill=blue!10,
     Cylinder body shade={left color=blue!30, right color=blue!60, middle color=blue!10},
     minimum width=+2cm,  shape border rotate=90,
  }]
\node[mycylinder, label=below:Betterer?] {};
\end{tikzpicture}
\end{document}

输出

在此处输入图片描述

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