\newpage
\subsection{Phase functions}
\label{sec:phase}
This section contains a description of all implemented medium scattering models, which
are also known as \emph{phase functions}. These are very similar in principle to surface
scattering models (or \emph{BSDF}s), and essentially describe where light travels after
hitting a particle within the medium.

The most commonly used models for smoke, fog, and other homogeneous media
are isotropic scattering (\pluginref{isotropic}) and the Henyey-Greenstein
phase function (\pluginref{hg}). Mitsuba also supports \emph{anisotropic}
media, where the behavior of the medium changes depending on the direction
of light propagation (e.g. in volumetric representations of fabric). These
are the Kajiya-Kay (\pluginref{kkay}) and Micro-flake (\pluginref{microflake})
models.

Finally, there is also a phase function for simulating scattering in
planetary atmospheres (\pluginref{rayleigh}).