Distance fog is a technique used in

3D computer graphics 3D computer graphics, sometimes called Computer-generated imagery, CGI, 3D-CGI or three-dimensional Computer-generated imagery, computer graphics, are graphics that use a three-dimensional representation of geometric data (often Cartesian coor ...

to enhance the

perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous syste ...

of distance by shading distant objects differently. Because many of the shapes in graphical environments are relatively simple, and complex

shadow A shadow is a dark area on a surface where light from a light source is blocked by an object. In contrast, shade occupies the three-dimensional volume behind an object with light in front of it. The cross-section of a shadow is a two-dimensio ...

s are difficult to render, many graphics engines employ a " fog"

gradient In vector calculus, the gradient of a scalar-valued differentiable function f of several variables is the vector field (or vector-valued function) \nabla f whose value at a point p gives the direction and the rate of fastest increase. The g ...

so objects further from the

camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...

are progressively more obscured by haze and by

aerial perspective Aerial perspective, or atmospheric perspective, is the effect the atmosphere has on the appearance of an object as viewed from a distance. As the distance between an object and a viewer increases, the contrast between the object and its backgro ...

. This technique simulates the effect of

light scattering In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radia ...

, which causes more distant objects to appear lower in contrast, especially in outdoor environments. CGfog

Visibility In meteorology, visibility is the measure of the distance at which an object or light can be clearly discerned. It depends on the Transparency and translucency, transparency of the surrounding air and as such, it is unchanging no matter the amb ...

in a natural haze declines exponentially, not linearly, with distance due to

scattering In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiat ...

. The colour of the light being scattered into the viewing path affects the 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 viewing distances, and 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 In geometry, a polygon () is a plane figure made up of line segments connected to form a closed polygonal chain. The segments of a closed polygonal chain are called its '' edges'' or ''sides''. The points where two edges meet are the polygon ...

s would appear at a sufficiently far distance that they were obscured by the fog, fading in as the player approached.

References

{{Reflist 3D rendering

See also

References