Shader

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In computer graphics, a shader is a computer program that calculates the appropriate levels of light, darkness, and color during the rendering of a 3D scene—a process known as shading. Shaders have evolved to perform a variety of specialized functions in computer graphics special effects and video post-processing, as well as general-purpose computing on graphics processing units.

Traditional shaders calculate rendering effects on graphics hardware with a high degree of flexibility. Most shaders are coded for (and run on) a graphics processing unit (GPU),^[1] though this is not a strict requirement. Shading languages are used to program the GPU's rendering pipeline, which has mostly superseded the fixed-function pipeline of the past that only allowed for common geometry transforming and pixel-shading functions; with shaders, customized effects can be used. The position and color (hue, saturation, brightness, and contrast) of all pixels, vertices, and/or textures used to construct a final rendered image can be altered using algorithms defined in a shader, and can be modified by external variables or textures introduced by the computer program calling the shader.^{[citation needed]}

Shaders are used widely in cinema post-processing, computer-generated imagery, and video games to produce a range of effects. Beyond simple lighting models, more complex uses of shaders include: altering the hue, saturation, brightness (HSL/HSV) or contrast of an image; producing blur, light bloom, volumetric lighting, normal mapping (for depth effects), bokeh, cel shading, posterization, bump mapping, distortion, chroma keying (for so-called "bluescreen/greenscreen" effects), edge and motion detection, as well as psychedelic effects such as those seen in the demoscene.^{[clarification needed]}