TikZによる連成振動アニメーション (1) ～ アニメーションGIF篇 http://doratex.hatenablog.jp/entry/20140417/1397742060

oscillation.tex

\documentclass{article}
\usepackage[papersize={10.8cm,2.6cm},margin=1mm,noheadfoot]{geometry}
\usepackage{tikz}
\usetikzlibrary{calc,patterns,decorations.pathmorphing}
\usepackage[nomessages]{fp}
\pagestyle{empty}
\setlength\parindent{0pt}

\begin{document}

%%%% \A*cos(\OMEGA*\t)+\B*sin(1.73*\OMEGA*\t) のパラメータ
\def\A{1}
\def\B{0.8}
\def\OMEGA{0.2}

%%% 壁などの描画のパラメータ
\def\wallHeight{2}
\def\wallWidth{0.2}
\def\totalLength{10}
\def\springStraightLength{0.2}
\def\axisDepth{-0.7}

%%% 壁などのスタイル
\tikzset{wall/.style={pattern = north east lines}}
\tikzset{ball/.style={circle,shade,outer color=black!90!white,inner color=white,inner sep=2.5mm,label={$m$}}}
\tikzset{spring/.style={decorate,decoration={aspect=0.4, segment length=#1, amplitude=2mm,coil}}}
\tikzset{springk/.style={label={$k$},yshift=2}}

\foreach \t in {0,1,...,199}{%
\FPeval\u{\A*cos(\OMEGA*\t)+\B*sin(1.73*\OMEGA*\t)}%
\FPeval\v{\A*cos(\OMEGA*\t)-\B*sin(1.73*\OMEGA*\t)}%
\centering
\begin{tikzpicture}[>=stealth]
%%% 左壁
\coordinate (south east of left wall) at (0,-.5*\wallHeight);
\coordinate (north west of left wall) at ($(south east of left wall) + (-\wallWidth,\wallHeight)$);
\fill[wall] (south east of left wall) rectangle (north west of left wall);
\draw[thick] (south east of left wall) -- (south east of left wall |- north west of left wall);
%%% 右壁
\coordinate (south west of right wall) at (\totalLength,-.5*\wallHeight);
\coordinate (north east of right wall) at ($(south west of right wall) + (\wallWidth,\wallHeight)$);
\fill[wall] (south west of right wall) rectangle (north east of right wall);
\draw[thick] (south west of right wall) -- (south west of right wall |- north east of right wall);
%%% おもり
\node[ball] (a) at (\totalLength/3 + \u,0) {};
\node[ball] (b) at (2*\totalLength/3 + \v,0) {};
%%% 座標軸
\draw[->] (0.5,\axisDepth) -- +(\totalLength-1,0);
\draw[dotted,thick] (\totalLength/3,\axisDepth-0.3) -- +(0,1.6)
              (2*\totalLength/3,\axisDepth-0.3) -- +(0,1.6)
              (a.south |- south east of left wall) -- (a.south)
              (b.south |- south east of left wall) -- (b.south);
\draw[->] (\totalLength/3,\axisDepth-0.15) --node[below] {$x_1$} +(\u,0);
\draw[->] (2*\totalLength/3,\axisDepth-0.15) --node[below] {$x_2$} +(\v,0);
%%% 座標計算
\coordinate (0) at (0,0);
\coordinate (0-right) at (\springStraightLength,0);
\coordinate (a-left) at ($(a.west) + (0.1-\springStraightLength,0)$);
\coordinate (a-right) at ($(a.east) + (\springStraightLength,0)$);
\coordinate (b-left) at ($(b.west) + (0.1-\springStraightLength,0)$);
\coordinate (b-right) at ($(b.east) + (\springStraightLength,0)$);
\coordinate (c-left) at (\totalLength + 0.1-\springStraightLength,0);
\coordinate (c) at (\totalLength,0);
%%% バネの直線部
\draw (0) -- (0-right)
      (a-left) -- (a.west)
      (a.east) -- (a-right)
      (b-left) -- (b.west)
      (b.east) -- (b-right)
      (c-left) -- (c);
%%% バネのグルグル部
\draw[spring={\totalLength/3 + \u}] (0-right) -- node[springk]{} (a-left);
\draw[spring={\totalLength/3 + \v - \u}] (a-right) -- node[springk]{} (b-left);
\draw[spring={\totalLength/3 - \v}] (b-right) -- node[springk]{} (c-left);
\end{tikzpicture}
\newpage
}

\end{document}