Method and apparatus for line anti-aliasing

Details Method and apparatus for line anti-aliasing Method and apparatus for line anti-aliasing

1998-01-07

2002-01-08

Zimmerman, Mark (Department: 2671)

Computer graphics processing and selective visual display system

Computer graphics processing

Shape generating

Reexamination Certificate

active

06337686

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to video graphics processing, and more particularly, to video graphics processing of line anti-aliasing.
BACKGROUND OF THE INVENTION
The basic architecture of a computing device is known to include a central processing unit (“CPU”), system memory, input/output ports, an address generation unit (“AGU”), program control circuitry, interconnecting buses, audio processing circuitry, and video processing circuitry. As the technology of the computing device elements continues to advance, computing devices are being used in more and more commercial applications. For example, computer devices are used in video game players, personal computers, work stations, video cameras, video recorders, televisions, etc. The technological advances are also enhancing video quality, audio quality, and the speed at which computing devices can process data. The enhancements of video quality are a direct result of video graphic circuit evolution.
Video graphics circuits have evolved from providing simple text and two-dimensional images to relatively complex three-dimensional images. Such evolution began with high-end computers such as workstations, where the use of complex and costly circuitry is more commercially viable. For example, anti-aliasing started with high-end computers. In general, anti-aliasing is a technique that visually compensates for jagged edges of displayed images that result because of the finite size of pixels. The visual compensation begins by creating subpixel masks for each object that is to be drawn within a pixel. The resulting subpixel masks for a pixel are then processed to produce pixel information for the given pixel. For example, assume that three objects are partially contained within a pixel. The first object has twenty-five percent (25%) coverage of the pixel. The second object has thirty percent (30%) coverage and the third object has twenty-five percent (25%) coverage of the pixel. The remaining twenty percent (20%) of the pixel is covered by background information. Once this data is obtained, the pixel information for the pixel is created from proportional contributions of pixel information of each object and the background.
The basis process of generating and utilizing subpixel masks has been discussed in several prior art references such as “A new simple and efficient anti-aliasing with subpixel masks” by Andreas Schilling, et. al, Computer Graphics, volume 25, number 4, July 1991, and “the A-buffer, an anti-alias surface method” by Loren Carpenter, Computer Graphics, volume 18, number 3, July 1984. While each of these references discuss a viable means for producing anti-aliasing, the schemes were not designed in terms of optimizing memory requirements. Nor were these techniques designed to take advantage of existing video processing technology.
As is known, the amount of memory required for any processing device directly affects the cost of the processing device. Thus, the more memory requirements can be reduced, the more inexpensively the processing device can be produced. To make anti-aliasing commercially viable to the general public, the cost of video graphic processing circuits needs to be reduced by reducing the memory requirements and taking advantage of existing video graphic processing techniques. Therefore, a need exists for a commercially viable video graphics processing method and apparatus that performs line anti-aliasing.


REFERENCES:
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Schilling, “A New Simple and Efficient Antialiasing with Subpixel Masks”Jul. 1991.*
Lathrop et al., “Accurate rendering by subpixel addressing”, Sep. 1990.*
Foley et al.,Computer Graphics: Principles and Practice, Second Edition Inc., pp. 132-137, 1995.

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