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\subsection{Emitters}
\label{sec:emitters}
Mitsuba supports a wide range of emitters/light sources, which can be classified
into two main categories: emitters which are located somewhere within the scene, and emitters
that \emph{surround} the scene to simulate a distant environment. An overview of the available
types is shown below:
\begin{figure}[h!]
\centering
\includegraphics[width=15.5cm]{images/emitter_overview.pdf}
\caption{
    Schematic overview of the most important emitters in Mitsuba.
    The arrows indicate the directional distribution of light.
}
\end{figure}
\newpage
Generally, light sources are specified as children of the \code{&lt;scene&gt;} element; for instance,
the following snippet instantiates a point light emitter that illuminates a sphere.
\begin{xml}
&lt;scene version=$\MtsVer$&gt;
	&lt;emitter type="point"&gt;
		&lt;spectrum name="intensity" value="1"/&gt;
		&lt;point name="position" x="0" y="0" z="-2"/&gt;
	&lt;/emitter&gt;
	&lt;shape type="sphere"/&gt;
&lt;/scene&gt;
\end{xml}
An exception to this are \emph{area lights}, which turn a geometric object into a light source.
These are specified as children of the corresponding \code{&lt;shape&gt;} element.
\begin{xml}
&lt;scene version=$\MtsVer$&gt;
	&lt;shape type="sphere"&gt;
		&lt;emitter type="area"&gt;
			&lt;spectrum name="radiance" value="1"/&gt;
		&lt;/emitter&gt;
	&lt;/shape&gt;
&lt;/scene&gt;
\end{xml}
Note the parameter names used to specify the light source power, which reflect
the different associated physical units.
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