\section{Lines of \Index{intersecting planes}}

For every object of the type \Lcs{psSolid}, it is possible to draw the lines
of intersection between a chosen solid and one or more planes.

The numeric argument \texttt{\Lkeyword{intersectiontype}=$k$} (value $-1$ by default)
determines whether or not to draw the intersection lines. Set to $0$, the
intersection lines are drawn.

There are three keys to be handled:

\begin{itemize}

\item \texttt{\Lkeyword{intersectionplan}=\{[$eq_1$] ... [$eq_n$]\}}
defines a list of the equations $eq_i$ of the intersecting planes. The $eq_i$
could as well be some objects from the type \Lkeyword{plan} (see the related section).
\begin{equation*}
  ax+by+cz+d=0    \qquad \text{that would deliver $[a\, b\, c\, d\,]$ as one of the $n$ equations}
\end{equation*}

\item \texttt{\Lkeyword{intersectionlinewidth}=$w_1$ ... $w_n$}
defines a list of the thickness in picas $w_i$ for each of the intersection lines.

\item \texttt{\Lkeyword{intersectioncolor}=color$_1$ ... color$_n$}
defines a list for the colors of the intersection lines.

\end{itemize}

\begin{LTXexample}[width=6cm]
\psset{lightsrc=20 -20 10,viewpoint=50 -20 10 rtp2xyz,Decran=50}
\psset{unit=0.5}
\begin{pspicture*}(-5,-4)(5,5)
\psSolid[object=cube,
   intersectiontype=0,
   intersectionplan={[1 0 .5 2] [1 0 .5 -1]},
   intersectionlinewidth=1 2,
   intersectioncolor=(bleu) (rouge),
   RotX=20,RotY=90,RotZ=30,
   a=6,
   action=draw*]
\end{pspicture*}
\end{LTXexample}

\endinput