graphics pipeline

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graphics pipeline

In 3D graphics rendering, the stages required to transform a three-dimensional image into a two-dimensional screen. The stages are responsible for processing information initially provided just as properties at the end points (vertices) or control points of the geometric primitives used to describe what is to be rendered. The typical primitives in 3D graphics are lines and triangles. The type of properties provided per vertex include x-y-z coordinates, RGB values, translucency, texture, reflectivity and other characteristics.

An Assembly Line
Graphics rendering is like a manufacturing assembly line with each stage adding something to the previous one. Within a graphics processor, all stages are working in parallel. Because of this pipeline architecture, today's graphics processing units (GPUs) perform billions of geometry calculations per second. They are increasingly designed with more memory and more stages, so that more data can be worked on at the same time.

The Goal
For gamers, photorealistic rendering at full speed is the goal, and human skin and facial expressions are the most difficult. Although there are always faster adapters on the market with more memory and advanced circuitry that render 3D action more realistically, thus far, no game has fooled anyone into believing a real person is on screen, except perhaps for a few seconds.


The Pipeline
These are the various stages in the typical pipeline of a modern graphics processing unit (GPU). (Illustration courtesy of NVIDIA Corporation.)






Bus interface/Front End
Interface to the system to send and receive data and commands.

Vertex Processing
Converts each vertex into a 2D screen position, and lighting may be applied to determine its color. A programmable vertex shader enables the application to perform custom transformations for effects such as warping or deformations of a shape.

Clipping
This removes the parts of the image that are not visible in the 2D screen view such as the backsides of objects or areas that the application or window system covers.

Primitive Assembly, Triangle Setup
Vertices are collected and converted into triangles. Information is generated that will allow later stages to accurately generate the attributes of every pixel associated with the triangle.

Rasterization
The triangles are filled with pixels known as "fragments," which may or may not wind up in the frame buffer if there is no change to that pixel or if it winds up being hidden.

Occlusion Culling
Removes pixels that are hidden (occluded) by other objects in the scene.

Parameter Interpolation
The values for each pixel that were rasterized are computed, based on color, fog, texture, etc.

Pixel Shader
This stage adds textures and final colors to the fragments. Also called a "fragment shader," a programmable pixel shader enables the application to combine a pixel's attributes, such as color, depth and position on screen, with textures in a user-defined way to generate custom shading effects.

Pixel Engines
Mathematically combine the final fragment color, its coverage and degree of transparency with the existing data stored at the associated 2D location in the frame buffer to produce the final color for the pixel to be stored at that location. Output is a depth (Z) value for the pixel.

Frame Buffer Controller
The frame buffer controller interfaces to the physical memory used to hold the actual pixel values displayed on screen. The frame buffer memory is also often used to store graphics commands, textures as well as other attributes associated with each pixel.
References in periodicals archive ?
For database administrators, ETL developers, data architects, programmers, and others, this guide explains the features of Microsoft SQL Server Integration Services when used as an import/export wizard, ETL tool, control flow engine, application platform, or high-performance data transformation pipeline.
Estimates of flow speeds in the subpolar gyre suggest a transit time of about a decade for a parcel of water that enters the transformation pipeline east of Newfoundland with a temperature of 12 [degrees] to 14 [degrees] C, travels counterclockwise, and emerges from the pipeline in the Labrador Basin at temperatures colder than 4 [degrees] C.
LSW temperature similarly depends first on the temperature history of the product emerging from the warm water transformation pipeline into the Labrador Basin plus the rate of that flow, and second on the history of the heat exchange between the Labrador Basin waters and the overlying atmosphere and surrounding ocean (sort of an uninsulated tub
Periods of relatively warm SST anomalies along the transformation pipeline correspond to periods when LSW warmed, and periods of relatively cold SST anomalies to periods when LSW cooled.
Thus as the warm SST anomaly traversed the transformation pipeline, the deep winter convection temperatures were warmer than usual.
This warming trend continued in the more northern area through 1966-72, but reversed to cooling in the upstream part of the transformation pipeline between Newfoundland and Ireland.
Conversely, in the period of strengthening westerlies in the 1970s and 1980s, not only was the transformation pipeline running cold, but the loss of heat from the ocean to the atmosphere over the Labrador Basin was progressively enhanced, reinforcing the LSW cooling trend.
Intended for C++ programmers familiar with computer graphics, the book describes the OpenGL drawing primitive types and how to render them with the vertex array and buffer object features, the transformation pipeline, lighting parameters, pixel rectangles, and 2D texture mapping.
The new release also provides extended data transformation pipelines, improved text mining, search and analytics capabilities and additional language support.

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