LaTeX-examples/documents/GeoTopo/figures/topology-halfspace.tex

\begin{tikzpicture}
    \draw [white,step=0.5cm, pattern=north east lines] (0,0) rectangle (2,1);
    \draw[very thick] (0,0) -- (2,0);

    \node at (2.4,0.5) {$\stackrel{\sim}{=}$};

\begin{scope}[shift={(4,0)}]
    \draw[white,pattern=north east lines] ([shift={(180:1cm)}]-0.0,0) arc (180:0:1cm);
    \draw[very thick] (-1,0) -- (1,0);
\end{scope}
\end{tikzpicture}