tex.sx-q-475141.tex

\documentclass[border=9,tikz]{standalone}
\usetikzlibrary{decorations.pathreplacing}
\begin{document}

\def\niterate{64}
\def\rolldice{
	\pgfmathsetmacro\rndlinewidth{6/(2+\i)}
	\pgfmathsetmacro\rndon{8+8*rnd}
	\pgfmathsetmacro\rndoff{2*rnd}
	\pgfmathsetmacro\rndshift{sqrt((1-\rndlinewidth/2)*10*rnd)}
	\pgfmathsetmacro\rndblend{50+\i*50*rand/\niterate}
}
\tikzset{
	put dashes/.style={
		/utils/exec=\rolldice,
		line width=\rndlinewidth,
		dash pattern=on \rndon off \rndoff,
		dash phase=(\rndon+\rndoff)*rnd,
		shift={(rnd*360:\rndshift pt)},
		line cap=round,
		blue!\rndblend!green,
		opacity=.6
	},
	brush/.style={
		decorate,
		decoration={
			show path construction,
			lineto code={
				\foreach\i in{1,...,\niterate}{
					\draw[put dashes]
						(\tikzinputsegmentfirst)--(\tikzinputsegmentlast);
				}
			},
			curveto code={
				\foreach\i in{1,...,\niterate}{
					\draw[put dashes]
						(\tikzinputsegmentfirst)..controls
						(\tikzinputsegmentsupporta)and(\tikzinputsegmentsupportb)
						..(\tikzinputsegmentlast);
				}
			},
			closepath code={
				\foreach\i in{1,...,\niterate}{
				\draw[put dashes]
					(\tikzinputsegmentfirst)--(\tikzinputsegmentlast);
				}
			}
		}
	}
}

\tikz{
	\draw(0,0)rectangle(100pt,100pt);
	\foreach\x in{2.5,7.5,...,99}{
		\xdef\ysofar{0}
		\foreach\y in{1,...,10}{
			\ifdim \ysofar pt < 99pt
				\pgfmathsetmacro\ystep{10+20*rnd}
				\pgfmathsetmacro\ytarget{\ysofar+\ystep}
				\ifdim \ytarget pt > 100pt
					\pgfmathsetmacro\ytarget{100}
				\fi
				\draw[brush](\x pt,\ysofar pt)--(\x pt,\ytarget pt);
				\xdef\ysofar{\ytarget}
			\fi
			
		}
	}
}

\message{^^J^^J time = \the\numexpr\pdfelapsedtime*1000/65536 ms ^^J^^J}

\end{document}