[Tex/LaTex] Morphing only a part of a full path in tikz

tikz-pgf

This might be a tikz newbie question but I have some trouble solving this.

I want to draw and fill a rectangular path where path morphing should be applied only to the upper side of the shape, more specifically I want to have an upper part with random steps. The rest of the path (left, lower and right sides) should just be straight lines. The shape should be closed and filled with one color.

My problem is that I cannot figure out how to apply the morphing only to the upper side and I suppose I cannot break up the path into different subpaths since I want to fill the final shape. Is there a way to use the morphing only on a part of the full path?
Another problem is that the cycle command does not really close the shape at the upper left corner.

I tried to find a solution in the tikz manual but there was nothing that really helped me.

Here is some example code:

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

\begin{document}

\usetikzlibrary{decorations.pathmorphing}
\begin{tikzpicture}

\draw[decorate, decoration={random steps,segment length=3.0mm, amplitude=2.0mm}, thick, rounded corners=1ex, fill=brown!70] (0,0) -- (4,0) -- ++(0, -1) -- ++(-4,0) -- cycle;


\end{tikzpicture}
\end{document}

Best Answer

You can use the decorate operation (don't use rounded corners with decoration or read carefully the answer to How to draw a decorated rectangle with rounded corners?):

enter image description here

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

\begin{document}
\begin{tikzpicture}
\draw[thick, fill=brown!70]
%
decorate[decoration={zigzag,segment length=1.0mm, amplitude=.2mm}]
{(0,0) -- ++(0,.5) -- ++(4,0) -- ++(0,-.5) }
%
[rounded corners=1ex]-- ++(0, -.5) -- ++(-4,0) -- cycle;
\end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] Reversing a path in TikZ

If you use PGFplots for plotting your functions, the paths will be reversed and connected appropriately by using stack plots=y in the axis options and issuing \closedcycle after the second plot:

\documentclass{article}

\usepackage{pgfplots}

\begin{document}

\begin{tikzpicture}
\begin{axis}[
    stack plots=y,
    hide axis
]
\addplot [draw=orange,thick]{x^2};
\addplot [draw=orange, thick, fill=yellow] {1} \closedcycle;
\end{axis}
\end{tikzpicture}

\end{document}

If all you want is the filled path, you can disable the axes by using hide axis.

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

Best Answer

Related Solutions

[Tex/LaTex] Reversing a path in TikZ

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

Related Question