1.3.6.1 Types of media

There are three types of media in POV-Ray: Emitting, absorbing and scattering. They have the following properties:

• Emitting: This is an additive media, which is handled as if it only emits light (note: it does not emit light to its surroundings like a light_source does; this just describes how it affects the rays going through it). That is, the color of the media is added to the color of the ray passing through it. Light sources do not have any effect at all in it (ie. it does not affect shadows in any way).
• Absorbing: This is a substractive media. This media substracts (absorbs) its coloration from the ray passing through it. Light sources are taken into account only in the shadow of the media (that is, absorbing media casts a shadow).
• Scattering: This is the most advanced media type as it fully takes into account light passing through it. That is, this media is lit by light sources (and thus, for example, nearby objects can cast shadows into the scattering media).

Emitting and absorbing medias are the simplest and thus fastest ones. Emitting media can be used for things like glows, lasers, sparkles and similar light-emitting effects. Absorbing media can be used for things like smoke and fog (the difference between the fog feature of POV-Ray is that the density of an absorbing media can be modified by a pattern and the media can be contained inside an object).

Scattering media is the more advanced and slower type. It is somewhat similar to absorbing media except that it is fully lit by light sources. This can be used for smoke or fog with visible lightbeams and shadows.