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A pixel shader is a type of shader program, often executed on a graphics processing unit. These programs are typically used to perform complex per-pixel effects. Microsoft's Direct3D and Silicon Graphics' OpenGL support shaders. (Note: In OpenGL parlance a pixel is called a fragment, so OpenGL calls these fragment shaders).



A pixel shader is a computation kernel function that computes color and other attributes of each pixel. Pixel shaders range from always outputting the same color, to applying a lighting value, to doing bump mapping, shadows, specular highlights, translucency and other phenomena. They can alter the depth of the pixel (for Z-buffering), or output more than one color if multiple render targets are active. A pixel shader alone cannot produce very complex effects, because it operates only on a single pixel, without knowledge of a scene's geometry or of neighboring pixels.


The term "Shader" originated with Pixar's RenderMan - a program that takes an entire description of a scene including camera positions, object geometry and renders the final output. RenderMan was introduced in 1989, but it wasn't until the 1995 release of Pixar's movie "Toy Story" that the general public was introduced to the power of RenderMan. Such computer-generated imagery (CGI) became more and more prolific in movies and television.

Consumer-level computer graphics hardware was also evolving rapidly and new features were implemented on "commodity" boards that rivaled expensive dedicated graphics workstations. The video game industry began to utilize newly-created powerful-yet-cheap 3D graphics hardware in PCs and game consoles. Light maps in particular were soon finding their way into games, followed by bump maps and procedural vertex generation. The continuing desire for more complex visual effects pushed the computing industry forward and previously fixed-function graphics processors received ever more programmable designs as manufacturing technology progressed. These more programmable GPUs allowed more complex effects, including pixel and vertex shader programs.


Pixel shaders use different languages depending on which API they use. Popular APIs include DirectX and OpenGL.




This chart describes the maximum supported Shader Model for various graphics processors. GPUs are usually backwards compatible as well.

PS version Direct3D version 3DLabs ATI Intel Matrox NVIDIA S3 Graphics SiS XGI
1.0/1.1 8.0 - - - - GeForce 3 series - Xabre-Series -
1.2 8.0a Wildcat VP - - - - - - -
1.3 8.0a - - - Parhelia series GeForce 4 Ti/4200Go series - Mirage 2 -
1.4 8.1 - Radeon R200 (8500-9250) - - - - - Volari V3 series (except V3XT)
2.0 9.0 Wildcat Realizm Radeon R300 (9500-9800, X300-X600) Intel GMA 900, 950, 3000, 3100 - - DeltaChrome, GammaChrome, Chrome S2x series Mirage 3, Mirage 3+ Volari V3XT, Volari V5 series, Volari V8 series, Volari 8300, Volari XP10
2.0a 9.0a - - - - - - -0.0
2.0b 9.0b - Radeon R420 (X700-X850) - - -GeForce FX series - - -
3.0 9.0c - Radeon R520 (X1300-X1950) Intel GMA X3000 GeForce 6 series, GeForce 7 series - - -
4.0 10 - Radeon R600 (HD 2400-HD 2900) Intel GMA X3100, X3500 - GeForce 8 series, GeForce 9 Series, GeForce 200 Series, Quadro FX 1700 - Mirage 4 -
4.1 10.1 - Radeon R600 (HD 3xxx), Radeon R700 (HD 4xxx) Intel GMA 500 - - Chrome 400 Series -
5.0 11 - Radeon R800 (HD 5xxx) - - - - -

See also



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