\documentclass[preview]{standalone}
\usepackage{filecontents}
\begin{filecontents*}{limit.tex}
\documentclass[pstricks,border=12pt]{standalone}
\usepackage{multido}
\Large
\begin{document}
\multido{\r=3.0+-0.1}{30}{%
\begin{pspicture}(-1,0)(6,2)
\psline{->}(-1,1)(5,1)
\pscircle*[linecolor=red](0,1){2pt}
\psframe*[linecolor=cyan,opacity=0.5](0,0)(\r,2)
\uput[-135](0,1){$t$}
\uput[0](5,1){time}
\end{pspicture}}
\end{document}
\end{filecontents*}
\usepackage{pgffor,animate}
\foreach \compiler/\ext in {latex/tex,dvips/dvi,ps2pdf/ps}