Fixed-function is a term canonically used to contrast 3D graphics APIs and earlier

GPU A graphics processing unit (GPU) is a specialized electronic circuit designed to manipulate and alter memory to accelerate the creation of images in a frame buffer intended for output to a display device. GPUs are used in embedded systems, mobi ...

s designed prior to the advent of

shader 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 speci ...

-based 3D graphics APIs and GPU architectures.

History

Historically fixed-function APIs consisted of a set of function entry points that would approximately or directly map to dedicated logic for their named purpose in

s designed to support them. As

based GPUs and APIs evolved, fixed-function APIs were implemented by graphics driver engineers using the more general purpose shading architecture. This approach served as a segue that would continue providing the fixed-function API abstraction most developers were experienced with while allowing further development and enhancements of the newer shader-based architectures.

OpenGL OpenGL (Open Graphics Library) is a cross-language, cross-platform application programming interface (API) for rendering 2D and 3D vector graphics. The API is typically used to interact with a graphics processing unit (GPU), to achieve hardwa ...

OpenGL ES OpenGL for Embedded Systems (OpenGL ES or GLES) is a subset of the OpenGL computer graphics rendering application programming interface (API) for rendering 2D and 3D computer graphics such as those used by video games, typically hardware-accele ...

and

DirectX Microsoft DirectX is a collection of application programming interfaces (APIs) for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with "Direct" ...

(

Direct3D Direct3D is a graphics application programming interface (API) for Microsoft Windows. Part of DirectX, Direct3D is used to render three-dimensional graphics in applications where performance is important, such as games. Direct3D uses hardware ...

) are all 3D graphics APIs that went through the transition from the fixed-function programming model to the shader-based programming model. Below is a table of when the transition from fixed-function to shaders was made: {, class="wikitable" , - ! 3D API !! Last Fixed-function Version !! First Shader Version , - , OpenGL , , v1.5 , , v2.0 , - , OpenGL ES , , v1.1 , , v2.0 , - , DirectX , , v7.0 , , v8.0

Fixed function vs shaders

Fixed function APIs tend to be a simpler programming abstraction with a series of well-defined and specifically named

graphics pipeline In computer graphics, a computer graphics pipeline, rendering pipeline or simply graphics pipeline, is a conceptual model that describes what steps a graphics system needs to perform to render a 3D scene to a 2D screen. Once ...

stages. Shader-based APIs treat graphics data (vertices and

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...

s / texels) generically and allow a great deal of flexibility in how this data is modulated. More sophisticated rendering techniques are possible using a

-based API. 3D rendering