Bloom (shader effect)
Encyclopedia
Computer graphics
Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....
effect used in computer games
Computer Games
"Computer Games" is a single by New Zealand group, Mi-Sex released in 1979 in Australia and New Zealand and in 1981 throughout Europe. It was the single that launched the band, and was hugely popular, particularly in Australia and New Zealand...
, demos
Demo (computer programming)
A demo is a non-interactive multimedia presentation made within the computer subculture known as the demoscene. Demogroups create demos to demonstrate their abilities in programming, music, drawing, and 3D modeling...
and high dynamic range rendering
High dynamic range rendering
In 3D computer graphics, high dynamic range rendering , also known as high dynamic range lighting, is the rendering of computer graphics scenes by using lighting calculations done in a larger dynamic range. This allows preservation of details that may be lost due to limiting contrast ratios...
(HDR) to reproduce an imaging artifact of real-world cameras. The effect produces fringes (or feathers) of light around very bright objects in an image, obscuring fine details. Basically, if an object has a light behind it, the light will look more realistic and will somewhat overlap the front of the object from the 3rd person perspective.
Theory
The physical basis of bloom is that, in the real world, lenses can never focus perfectly. Even a perfect lens will convolveConvolution
In mathematics and, in particular, functional analysis, convolution is a mathematical operation on two functions f and g, producing a third function that is typically viewed as a modified version of one of the original functions. Convolution is similar to cross-correlation...
the incoming image with an Airy disc
Airy disc
In optics, the Airy disk and Airy pattern are descriptions of the best focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light....
(the diffraction pattern produced by passing a point light source through a circular aperture) . Under normal circumstances, these imperfections aren't noticeable, but an intensely bright light source will cause the imperfections to become visible. As a result, the image of the bright light appears to bleed beyond its natural borders.
The Airy disc function falls off very quickly but has very wide tails (actually, infinitely wide tails). As long as the brightness of adjacent parts of the image are roughly in the same range, the effect of the blurring caused by the Airy disc is not particularly noticeable; but in parts of the image where very bright parts are adjacent to relatively darker parts, the tails of the Airy disc become visible, and can extend far beyond the extent of the bright part of the image.
In HDR images, the effect can be re-produced by convolving the image with a windowed kernel of an Airy disc (for very good lenses), or by applying Gaussian blur
Gaussian blur
A Gaussian blur is the result of blurring an image by a Gaussian function. It is a widely used effect in graphics software, typically to reduce image noise and reduce detail...
(to simulate the effect of a less perfect lens), before converting the image to fixed-range pixels. The effect can't be fully reproduced in non-HDR imaging systems, because the amount of bleed depends on how bright the bright part of the image is.
As an example, if a picture is taken indoors, the brightness of outdoor objects seen through a window may be 70 or 80 times brighter than objects inside the room. If exposure levels are set for objects inside the room, windows will be bright enough, when convolved with the Airy disc of the camera being used to produce the image, to cause the image of the windows to bleed past the frames of the window.
Practical implementation
Current generation gaming systems are able to render 3D graphics using floating point frame buffers, in order to produce HDR images. To produce the bloom effect, the HDR images in the frame buffer are convolved with a convolution kernel in a post-processing step, before converting to RGB space. The convolution step usually requires the use of a large gaussian kernel that is not practical for realtime graphics, causing the programmers to use approximation methods.Use in games
IcoIco
is an action-adventure game published by Sony Computer Entertainment and released for the PlayStation 2 video game console. It was designed and directed by Fumito Ueda, who wanted to create a minimalist game around a "boy meets girl" concept. Originally planned for the PlayStation, Ico took...
was one of the earliest games to use the bloom effect. Bloom lighting has been used in many games, modifications, and game engines such as Quake Live
Quake Live
Quake Live is a first-person shooter video game by id Software designed to run on x86-based computers running Microsoft Windows, Mac OS X or Linux that is downloaded and launched via a web browser plugin. It is a variant of its predecessor, Quake III Arena .Quake Live is free to download and play...
, Cube 2: Sauerbraten and the Spring game engine. The effect is popular in current generation games, and is used heavily in PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
, Xbox 360
Xbox 360
The Xbox 360 is the second video game console produced by Microsoft and the successor to the Xbox. The Xbox 360 competes with Sony's PlayStation 3 and Nintendo's Wii as part of the seventh generation of video game consoles...
and PlayStation 3
PlayStation 3
The is the third home video game console produced by Sony Computer Entertainment and the successor to the PlayStation 2 as part of the PlayStation series. The PlayStation 3 competes with Microsoft's Xbox 360 and Nintendo's Wii as part of the seventh generation of video game consoles...
games as well as the popular Nintendo GameCube
Nintendo GameCube
The , officially abbreviated to NGC in Japan and GCN in other regions, is a sixth generation video game console released by Nintendo on September 15, 2001 in Japan, November 18, 2001 in North America, May 3, 2002 in Europe, and May 17, 2002 in Australia...
and Wii
Wii
The Wii is a home video game console released by Nintendo on November 19, 2006. As a seventh-generation console, the Wii primarily competes with Microsoft's Xbox 360 and Sony's PlayStation 3. Nintendo states that its console targets a broader demographic than that of the two others...
releases, The Legend of Zelda: Twilight Princess
The Legend of Zelda: Twilight Princess
is an action-adventure game developed by Nintendo Entertainment Analysis and Development, and published by Nintendo for the GameCube and Wii video game consoles. It is the thirteenth installment in The Legend of Zelda series...
, Metroid Prime
Metroid Prime
Metroid Prime is a video game developed by Retro Studios and Nintendo for the Nintendo GameCube, released in North America on November 17, 2002...
, and Metroid Prime 2: Echoes
Metroid Prime 2: Echoes
Metroid Prime 2: Echoes, known as in Japan, is a first-person, action-adventure video game developed by Retro Studios and published by Nintendo for the GameCube video game console. It is the seventh game in the Metroid series, a direct sequel to Metroid Prime, and the first game in the series with...
. The Wii game Little King's Story
Little King's Story
is a life simulation/role-playing video game co-developed by Cing and Town Factory for the Wii. The game was published by Rising Star Games in PAL regions on April 24, 2009, by Xseed Games in North America on July 21, 2009, and by Marvelous Entertainment in Japan on September 3, 2009.The player...
also utilizes the effect to give the game a fantasy look, which combines storybook elements and colorful environments. Transformers: The Game
Transformers: The Game
Transformers: The Game is the name of multiple versions of a video game based on the 2007 live action film Transformers, all of which were released in North America in June 2007. Home console and PC versions were developed by Traveller's Tales for the PlayStation 2, Xbox 360, Wii, PlayStation 3 and...
and Transformers: Revenge of the Fallen (video game)
Transformers: Revenge of the Fallen (video game)
Transformers: Revenge of the Fallen: The Game is a 2009 third-person shooter video game based on the 2009 live action film Transformers: Revenge of the Fallen. The PlayStation 3 and Xbox 360 versions were developed by Luxoflux, and ported to the PC by Beenox Studios...
also uses bloom effect. TES4 Oblivion also uses this effect.
See also
- Afterimage (shader effect)Afterimage (shader effect)Afterimage is a computer graphics effect used by computer games. The effect takes the bright parts of a rendered image of the scene, and then fades in a motion blur style fashion as the scene progresses. The result is that bright areas leave a fading trail when the camera is moving. Afterimage can...
, sometimes used to enhance the bloom effect. - Chromatic aberrationChromatic aberrationIn optics, chromatic aberration is a type of distortion in which there is a failure of a lens to focus all colors to the same convergence point. It occurs because lenses have a different refractive index for different wavelengths of light...
- Tone mappingTone mappingTone mapping is a technique used in image processing and computer graphics to map one set of colors to another in order to approximate the appearance of high dynamic range images in a medium that has a more limited dynamic range...