In 3D computer graphics, the graphics pipeline or rendering pipeline refers to the sequence of steps used to create a 2D raster representation of a 3D scene. Plainly speaking, once a 3D model has been created, for instance in a video game or any other 3D computer animation, the graphics pipeline is the process of turning that 3D model into what the computer displays. In the early history of 3D computer graphics, fixed purpose hardware was used to speed up the steps of the pipeline through a fixed-function pipeline. Later, the hardware evolved, becoming more general purpose, allowing greater flexibility in graphics rendering as well as more generalized hardware, and allowing the same generalized hardware to perform not only different steps of the pipeline, like in fixed purpose hardware, but even in limited forms of general purpose computing. As the hardware evolved, so did the graphics pipelines, the OpenGL, and DirectX pipelines, but the general concept of the pipeline remains the same.