Earlier versions of POV-Ray used a feature called halo
to simulate fine particles such as smoke, steam, fog, or flames. The halo
statement was part of the texture
statement. This feature has been discontinued and replaced by the interior
and media
statements which are object modifiers outside the texture
statement.
See "Why are Interior and Media Necessary?" for a detailed explanation on the reasons for the change. See "Media" for details on media
.