The first picture draws an impossible brick, which induces an optical illusion similar to that triggered by Escher's impossible cube.
The second picture draws a Penrose triangle, another similar optical illusion.
Edit and compile if you like:
% Author: Julien Cretel % Date: 24/02/2013 \documentclass{article} \usepackage{tikz} \usepackage[active,tightpage]{preview} \PreviewEnvironment{center} \setlength\PreviewBorder{20pt}% \begin{document} \begin{center} \begin{tikzpicture}[scale=4.5, line join=bevel] % \a and \b are two macros defining characteristic % dimensions of the impossible brick. \pgfmathsetmacro{\a}{0.18} \pgfmathsetmacro{\b}{1.37} \tikzset{% apply style/.code={\tikzset{#1}}, brick_edges/.style={thick,draw=black}, face_colourA/.style={fill=gray!50}, face_colourB/.style={fill=gray!25}, face_colourC/.style={fill=gray!90}, } \foreach \theta/\v/\facestyleone/\facestyletwo in {% 0/0/{brick_edges,face_colourA}/{brick_edges,face_colourC}, 180/-\a/{brick_edges,face_colourB}/{brick_edges,face_colourC} }{ \begin{scope}[rotate=\theta,shift={(\v,0)}] \draw[apply style/.expand once=\facestyleone] ({-.5*\b},{1.5*\a}) -- ++(\b,0) -- ++(-\a,-\a) -- ++({-\b+2*\a},0) -- ++(0,-{2*\a}) -- ++(\b,0) -- ++(-\a,-\a) -- ++(-\b,0) -- cycle; \draw[apply style/.expand once=\facestyletwo] ({.5*\b},{1.5*\a}) -- ++(0,{-2*\a}) -- ++(-\a,0) -- ++(0,\a) -- cycle; \end{scope} } \end{tikzpicture} \vspace{1cm} \begin{tikzpicture}[scale=1, line join=bevel] % \a and \b are two macros defining characteristic % dimensions of the Penrose triangle. \pgfmathsetmacro{\a}{2.5} \pgfmathsetmacro{\b}{0.9} \tikzset{% apply style/.code = {\tikzset{#1}}, triangle_edges/.style = {thick,draw=black} } \foreach \theta/\facestyle in {% 0/{triangle_edges, fill = gray!50}, 120/{triangle_edges, fill = gray!25}, 240/{triangle_edges, fill = gray!90}% }{ \begin{scope}[rotate=\theta] \draw[apply style/.expand once=\facestyle] ({-sqrt(3)/2*\a},{-0.5*\a}) -- ++(-\b,0) -- ({0.5*\b},{\a+3*sqrt(3)/2*\b}) -- % higher point ({sqrt(3)/2*\a+2.5*\b},{-.5*\a-sqrt(3)/2*\b}) -- % rightmost point ++({-.5*\b},-{sqrt(3)/2*\b}) -- % lower point ({0.5*\b},{\a+sqrt(3)/2*\b}) -- cycle; \end{scope} } \end{tikzpicture} \end{center} \end{document}
Click to download: escher-brick-penrose-triangle.tex • escher-brick-penrose-triangle.pdf
Open in Overleaf: escher-brick-penrose-triangle.tex