2.3.2.1 Atmospheric Media
Atmospheric effects such as fog, dust, haze, or visible gas may be simulated by a media statement
specified in the scene but not attached to any object. All areas not inside a non-hollow object in the entire scene. A
very simple approach to add fog to a scene is explained in section "Fog" however this
kind of fog does not interact with any light sources like media does. It will not
show light beams or other effects and is therefore not very realistic.
The atmosphere media effect overcomes some of the fog's limitations by calculating the interaction between light
and the particles in the atmosphere using volume sampling. Thus shafts of light beams will become visible and objects
will cast shadows onto smoke or fog.
Note: POV-Ray cannot sample media along an infinitely long ray. The ray must be
finite in order to be possible to sample. This means that sampling media is only possible for rays that hit an object.
So no atmospheric media will show up against background or sky_sphere.
Another way of
being able to sample media is using spotlights because also in this case the ray is not infinite (it is sampled only
inside the spotlight cone).
With spotlights you will be able to create the best results because
their cone of light will become visible. Pointlights can be used to create effects like street lights in fog. Lights
can be made to not interact with the atmosphere by adding media_interaction off to the light source. They
can be used to increase the overall light level of the scene to make it look more realistic.
Complete details on media are given in the section "Media". Earlier
versions of POV-Ray used an atmosphere statement for atmospheric effects but that system was incompatible
with the old object halo system. So atmosphere has been eliminated and replaced with a
simpler and more powerful media feature. The user now only has to learn one media system for either
atmospheric or object use.
If you only want media effects in a particular area, you should use object media rather than only relying upon the
media pattern. In general it will be faster and more accurate because it only calculates inside the constraining
object.
Note: the atmosphere feature will not work if the camera is inside a non-hollow
object (see section "Empty and Solid Objects" for a detailed
explanation).
More about "Fog"
More about "media"
More about "Media"
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