They are or not parallels?

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Author

OSjerick

Last Updated

10 years ago

License

Creative Commons CC BY 4.0

Abstract

The perpendicular lines that do not match row to row create an illusion of the lines between them being not parallel.

Submitted as an answer to the Showcase of Optical Illusions question on TeX SX.

Click the Illusions tag below to see more!

Tags

TikZ Optical Illusions

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% Source: http://tex.stackexchange.com/a/149780/23931
\documentclass[tikz]{standalone}
\usetikzlibrary{calc}
\begin{document}
    \pagecolor{gray}
    \begin{tikzpicture}
        \pgfmathsetmacro{\offsety}{.05};
        \foreach \y / \offsetx in {0/0.3,1/0.5,2/0.3,3/0,4/0.3,5/0.5,6/0.3,7/0,8/0.3}
            \foreach \x in {0,...,10}{%
                \pgfmathifthenelse{mod(\x,2) == 0}{"black"}{"white"}
                %\ifodd\x \def\squarecolor{white} \else \def\squarecolor{black} \fi %Other way, use \squarecolor inside fill options
                \fill[\pgfmathresult] ($(\x,\y)+(\offsetx,\offsety*\y)$) rectangle +(1,1);
            }
    \end{tikzpicture}
\end{document}