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Geometric manipulation of modelling primitives, such as that performed by ageometry pipeline, is the first stage incomputer graphics systems which perform image generation based on geometric models. While geometry pipelines were originally implemented in software, they have become highly amenable to hardware implementation, particularly since the advent ofvery-large-scale integration (VLSI) in the early 1980s. A device called theGeometry Engine developed byJim Clark andMarc Hannah atStanford University in about 1981 was the watershed for what has since become an increasingly commoditized function in contemporary image-syntheticraster display systems.[1][2]
Geometric transformations are applied to the vertices ofpolygons, or other geometric objects used asmodelling primitives, as part of the first stage in a classical geometry-based graphic imagerendering pipeline. Geometric computations may also be applied to transform polygon or repairsurface normals, and then to perform thelighting andshading computations used in their subsequent rendering.
Hardware implementations of the geometry pipeline were introduced in the earlyEvans & SutherlandPicture System, but perhaps received broader recognition when later applied in the broad range of graphics systems products introduced bySilicon Graphics (SGI). Initially the SGI geometry hardware performed simplemodel space toscreen spaceviewing transformations with all the lighting and shading handled by a separate hardware implementation stage. In later, much higher performance applications, such as theRealityEngine, they began to be applied to perform part of the rendering support as well.
More recently, perhaps dating from the late 1990s, the hardware support required to perform the manipulation and rendering of quite complex scenes has become accessible to the consumer market. Companies such asNvidia andAMD Graphics (formerlyATI) are two current leading representatives of hardware vendors in this space. TheGeForce line ofgraphics cards from Nvidia was the first to support fullOpenGL andDirect3D hardware geometry processing in the consumer PC market, while some earlier products such as Rendition Verite incorporated hardware geometry processing through proprietary programming interfaces. On the whole, earlier graphics accelerators by3Dfx,Matrox and others relied on theCPU for geometry processing.
This subject matter is part of the technical foundation for modern computer graphics, and is a comprehensive topic taught at both the undergraduate and graduate levels as part of acomputer science education.