Editing Shader (section)

==== Pixel shaders ====
Pixel shaders, also known as [[fragment (computer graphics)|fragment]] shaders, compute [[color]] and other attributes of each "fragment": a unit of rendering work affecting at most a single output [[pixel]]. The simplest kinds of pixel shaders output one screen [[pixel]] as a color value; more complex shaders with multiple inputs/outputs are also possible.<ref>{{cite web|url=http://www.lighthouse3d.com/tutorials/glsl-tutorial/fragment-shader/|title=GLSL Tutorial – Fragment Shader|date=June 9, 2011}}</ref> Pixel shaders range from simply always outputting the same color, to applying a [[lighting]] value, to doing [[bump mapping]], [[shadows]], [[specular highlight]]s, [[translucency]] and other phenomena. They can alter the depth of the fragment (for [[Z-buffering]]), or output more than one color if multiple [[render target]]s are active. In 3D graphics, a pixel shader alone cannot produce some kinds of complex effects because it operates only on a single fragment, without knowledge of a scene's geometry (i.e. vertex data). However, pixel shaders do have knowledge of the screen coordinate being drawn, and can sample the screen and nearby pixels if the contents of the entire screen are passed as a texture to the shader. This technique can enable a wide variety of two-dimensional [[Post processing (images)|postprocessing]] effects such as [[Gaussian blur|blur]], or [[edge detection]]/enhancement for [[Cel shader|cartoon/cel shaders]]. Pixel shaders may also be applied in ''intermediate'' stages to any two-dimensional images—[[sprite (computer graphics)|sprite]]s or [[texture (computer graphics)|texture]]s—in the [[Graphics pipeline|pipeline]], whereas [[vertex shaders]] always require a 3D scene. For instance, a pixel shader is the only kind of shader that can act as a [[video postprocessing|postprocessor]] or [[video filter|filter]] for a [[video stream]] after it has been [[rasterization|rasterized]].