[Tex/LaTex] Amoeba shape with TikZ

diagramstikz-pgf

I would like to draw generic amoeba-like shapes with TikZ and don't really want to think too deeply about its boundary. Basically a closed connected set with smooth locally convex boundaries.

Any ideas how to do this easily?

Best Answer

More realistic amoeba with PSTricks.

First Version

Please skip this first version (as there is a small glitch) and jump to the final version.

In this version I use \psparametricplot. After meticulously figuring out its behavior, I noticed that the last node is always included to create the closed curve. As a result, the first node and the last node are on the same radial line that make the curve has a visual defect on the curved line joining them.

I have no idea how to exclude the last node when using \psparametricplot.

enter image description here

\documentclass[pstricks]{standalone}
\usepackage{pst-plot}
\psset
{
    plotstyle=ccurve,
    fillstyle=solid,
    fillcolor=gray,
}
\begin{document}
\begin{pspicture}(-3,-3)(3,3)
\psparametricplot[plotpoints=40]{0}{360}{/R rand 1001 mod 1000 div 1.5 add def R t PtoC}
\end{pspicture}
\end{document}

Animation

enter image description here

\documentclass[pstricks]{standalone}
\usepackage{pst-plot}
\psset
{
    plotstyle=ccurve,
    fillstyle=solid,
    fillcolor=gray,
}

\begin{document}
\multido{\i=4+4}{20}{%
\begin{pspicture}(-3,-3)(3,3)
\psparametricplot[plotpoints=\i]{0}{360}{/R rand 1001 mod 1000 div 1.5 add def R t PtoC}
\end{pspicture}}
\end{document}

Final version

In this version I use \curvepnodes to produce a list of nodes. \Pnodecount represents the index of the last element.

Therefore,

\multido{\i=0+1}{\Pnodecount}{\xdef\points{\points (P\i)}}

exludes the last node.

One advantage of using \curvepnodes is that we don't need to calculate the angle step.

enter image description here

\documentclass[pstricks]{standalone}

\usepackage{pst-node,pst-plot}
\psset{fillstyle=solid,fillcolor=gray}

\def\points{}
\pstVerb{666 srand}
\def\N{25}

\begin{document}
\begin{pspicture}(-3,-3)(3,3)
\curvepnodes[plotpoints=\N]{0}{360}{rand 16 mod 15 div 1.5 add t PtoC}{P}
\multido{\i=0+1}{\Pnodecount}{\xdef\points{\points (P\i)}}
\expandafter\psccurve\points
\end{pspicture}
\end{document}

Animation

enter image description here

\documentclass[pstricks]{standalone}

\usepackage{pst-node,pst-plot}
\usepackage{graphicx}

\newsavebox\IBox
\savebox\IBox{\includegraphics[width=6cm]{example-grid-100x100pt}}
\psset
{
    fillstyle=solid,
    fillcolor=gray,
    xunit=\dimexpr\wd\IBox/6,
    yunit=\dimexpr\ht\IBox/6,
}

\pstVerb{666 srand}

\begin{document}
\multido{\io=15+5}{10}{%
\def\points{}%
\begin{pspicture}(-3,-3)(3,3)
\curvepnodes[plotpoints=\io]{0}{360}{rand 16 mod 15 div 1.5 add t PtoC}{P}
\multido{\ii=0+1}{\Pnodecount}{\xdef\points{\points (P\ii)}}
\begin{psclip}{\expandafter\psccurve\points}
    \rput(0,0){\usebox\IBox}
\end{psclip}
\end{pspicture}}
\end{document}

Related Solutions

[Tex/LaTex] padded boundary of convex hull

In case anyone is interested, this is a small modification to Jake's answer: it simplifies a few of the calculations, and now works for a single node (in which case it draws a circle):

\newcommand{\convexpath}[2]{
  [   
  create hullcoords/.code={
    \global\edef\namelist{#1}
    \foreach [count=\counter] \nodename in \namelist {
      \global\edef\numberofnodes{\counter}
      \coordinate (hullcoord\counter) at (\nodename);
    }
    \coordinate (hullcoord0) at (hullcoord\numberofnodes);
    \pgfmathtruncatemacro\lastnumber{\numberofnodes+1}
    \coordinate (hullcoord\lastnumber) at (hullcoord1);
  },
  create hullcoords
  ]
  ($(hullcoord1)!#2!-90:(hullcoord0)$)
  \foreach [
  evaluate=\currentnode as \previousnode using \currentnode-1,
  evaluate=\currentnode as \nextnode using \currentnode+1
  ] \currentnode in {1,...,\numberofnodes} {
    let \p1 = ($(hullcoord\currentnode) - (hullcoord\previousnode)$),
    \n1 = {atan2(\x1,\y1) + 90},
    \p2 = ($(hullcoord\nextnode) - (hullcoord\currentnode)$),
    \n2 = {atan2(\x2,\y2) + 90},
    \n{delta} = {Mod(\n2-\n1,360) - 360}
    in 
    {arc [start angle=\n1, delta angle=\n{delta}, radius=#2]}
    -- ($(hullcoord\nextnode)!#2!-90:(hullcoord\currentnode)$) 
  }
}

Note if using the pgf/tikz >=3.0, you need to switch the arguments of atan2 (so atan2(\x1,\y1) becomes atan2(\y1,\x1). If you need to support multiple versions (for working with collaborators, uploading to arxiv, etc.) you can use \@ifpackagelater, e.g.

\@ifpackagelater{tikz}{2013/12/01}{...}{...}

[Tex/LaTex] Drawing a line between two points

enter image description here

\documentclass{article}
\usepackage{tikz}

\begin{document}
\begin{tikzpicture}
\draw (-3,-3) grid (3,3);
\draw (-2,2) -- (2,-3);
\end{tikzpicture}
\end{document}

Explanation

Define a canvas. (-3,-3) is the bottom left corner and (3,3) is the top right corner.
\draw (-2,2) -- (2,-3); draws a line from (-2,2) to (2,-3).
Compile the code with pdflatex or xelatex or latex-dvips-ps2pdf.
Done.

You can use \tikz{\draw (-2,2) -- (2,-3);} or \tikz\draw (-2,2) -- (2,-3); if you don't need tikzpicture.

Use the following to change the unit, put it anywhere before the \tikz or tikzpicture.

\tikzset
{
    x=2cm,% default value is 1cm.
    y=3cm,% default value is 1cm.
}

The last attempt:

\documentclass{article}
\usepackage{tikz}
\begin{document}
I want to draw a red line of thickness 1 mm, one unit in horizontal direction must be equal to 1.1 cm, and
one unit in vertical direction must be equal to 1.2 cm. Here is the line,
 \tikz[x=1.1cm,y=1.2cm]{\draw[line width=1mm,red](-1,1)--(1,-1);}, is it nice?
\end{document}

enter image description here

Best Answer

First Version

Animation

Final version

Animation

Related Solutions

[Tex/LaTex] padded boundary of convex hull

[Tex/LaTex] Drawing a line between two points

Explanation

Related Question