SUG: Note on environment variables

1 files changed, 27 insertions, 1 deletions

diff --git a/guide/ch_advanced_use.tex b/guide/ch_advanced_use.tex
index fbc4b58225..34fbd20e80 100644
--- a/guide/ch_advanced_use.tex
+++ b/guide/ch_advanced_use.tex
@@ -485,7 +485,7 @@ For example, using the option \texttt{-c\ my\_config.ini} would resolve to the f
 -\/-sky-date         & date       & The initial date in \texttt{yyyymmdd} format. \\
 -\/-sky-time         & time       & The initial time in \texttt{hh:mm:ss} format. \\\midrule
 -\/-startup-script   & script name & The name of a script to run after the program has started. [\file{startup.ssc}] \\\midrule
--\/-fov              & angle      & The initial vertical field of view in degrees. \\\midrule
+-\/-fov              & angle (degrees) & The initial vertical field of view in degrees. \\\midrule
 -\/-scale-gui        & scale factor & Scaling the GUI according to scale factor\\\midrule
 -\/-projection-type  & ptype      & The initial projection type (e.g. \texttt{perspective}). \\\midrule
 -\/-spout  or -S     & all or sky & Act as Spout sender (See section \ref{sec:CommandLineOptions:Special:Spout}).%
@@ -554,6 +554,32 @@ For permanent setting, use the Nvidia configuration dialog to configure Stellari
 
 Note that Spout use disables any multisampling setting (see Appendix~\ref{sec:config.ini:video}). 
 
+\subsection{Environment Variables}
+\label{sec:Environment}
+
+Some command-line options can be set permanently by storing them into
+environment variables. How to set them depends on the respective
+operating system. Calling the respective options on the command line
+still overrides an environment variable (apart from
+\texttt{STEL\_OPTS}).
+
+This may be especially helpful on Windows systems with older graphics
+cards which may not fully be compatible with OpenGL. Here we recommend
+you either use the program links using the ANGLE-related options, or
+you can set the environment variable once and forget about the
+problems.
+
+\begin{description}
+\item[STEL\_OPTS] may contain a default commandline with options in the syntax of the table above.
+\item[STEL\_USERDIR] may contain the path to a user data directory
+  deviating from the default (see section \ref{sec:Directories}).
+\item[QT\_OPENGL] (Windows only). May be one of \texttt{desktop} (native OpenGL for your GPU, recommended),
+  \texttt{angle} or \texttt{software}. The last activates pure software rendering using the MESA OpenGL library.
+\item[QT\_ANGLE\_PLATFORM] (Windows only). May be one of \texttt{d3d9} (DirectX~9) or \texttt{d3d11} (DirectX~11),
+  or \texttt{warp} for another software-only solution.
+\end{description}
+
+
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