Editing Distance fog

{{short description|In 3D graphics, obscuring distant objects with fog}}
{{More citations needed|date=September 2011}}
{{3D computer graphics}}

'''Distance fog''' is a technique used in [[3D computer graphics]] to enhance the [[depth perception|perception]] of distance by [[shading]] distant objects differently.<ref name="NGen15">{{cite magazine|title=The Next Generation 1996 Lexicon A to Z: Depth Shading|magazine=[[Next Generation (magazine)|Next Generation]]|issue=15 |publisher=[[Imagine Media]]|date=March 1996|page=32}}</ref>

Because many of the shapes in graphical environments are relatively simple, and complex [[shadow]]s are difficult to [[rendering (computer graphics)|render]], many [[Game engine|graphics engines]] employ a "[[fog]]" [[gradient]] so objects further from the [[virtual camera|camera]] are progressively more obscured by [[haze]] and by [[aerial perspective]].<ref>{{Cite book | last1 = Elena | first1 = Deza|author1-link=Elena Deza | last2 = Michel Deza | author2-link = Michel Deza | title = Encyclopedia of Distances | publisher = Springer-Verlag | year = 2009 | page = 513 | url = http://www.liga.ens.fr/~deza/495-528.pdf | access-date = 2011-09-25 | archive-url = https://web.archive.org/web/20120223143010/http://www.liga.ens.fr/~deza/495-528.pdf | archive-date = 2012-02-23 | url-status = dead }}</ref> This technique simulates the effect of [[diffraction|light scattering]], which causes more distant objects to appear lower in [[Contrast (vision)|contrast]], especially in outdoor environments.

[[File:CGfog.jpg|left|thumb|300px|Example of distance fog on the [[Utah teapot]]]]

[[Visibility]] in a natural haze [[Visibility#Derivation|declines exponentially]], not [[Linearity|linearly]], with distance due to [[scattering]]. The colour of the light being scattered into the viewing path affects the [[aerial perspective|colour of the haze]]; blue under blue skies, reddish near sunset, as with [[alpenglow]]. These more subtle details are represented in some graphics.

"Fogging" is another use of distance fog in mid-to-late 1990s games, when processing power was not enough to render far [[Draw distance|viewing distances]], and [[Clipping (computer graphics)|clipping]] was employed. Clipping could be very distracting since bits and pieces of polygons would flicker in and out of view instantly, and by applying a medium-ranged distance fog, the clipped [[polygon]]s would appear at a sufficiently far distance that they were obscured by the fog, fading in as the player approached.<ref name="NGen15"/> 

==See also==
* [[Aerial perspective]]
* [[Anisotropic filtering]]
* [[Computer graphics]]
* [[Draw distance]]
* [[Level of detail (computer graphics)|Level of detail (LOD)]]
* [[Scale space]]

==References==
{{Reflist}}

[[Category:3D rendering]]