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A pixel shader is a shader program, often executed on a graphics processing unit. It adds 3D shading and lighting effects to pixels in an image, for example those in video games. Microsoft's DirectX and Silicon Graphics' OpenGL support pixel shaders. In OpenGL a pixel shader is called a fragment shader.

Function

A pixel shader 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. 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. A pixel shader is a computation kernel function. Pixel shaders can alter the depth of the pixel (for Z-buffering), or output more than one color if multiple render targets are active.

Programming

Pixel shaders have been programmed in Assembly, Cg, GLSL, HLSL and other languages.

Compatibility

Hardware

This shows which cards, graphic chips, and DirectX-Version supports which Pixel-Shader-Version. Graphic chips usually are fully downward compatible (3.0 chip supports 2.0, 1.1, etc.).

(Italics indicate products that are not yet available.)

See also

• Direct3D
• Geometry shader
• Graphics pipeline
• OpenGL
• Vertex shader

References

• OpenGL Shading Language – Documentation of Shader in OpenGL
• GLSL Tutorial (engl.)
• OpenGL Shading Language examples
• Fundamentals of Pixel Shaders at Gamedev.net