Computer graphics processing and selective visual display system – Computer graphics processing – Three-dimension
Utility Patent
1997-07-02
2001-01-02
Brier, Jeffery (Department: 2779)
Computer graphics processing and selective visual display system
Computer graphics processing
Three-dimension
C345S419000
Utility Patent
active
06169553
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to video graphics processing and more particularly to video graphics processing of a three-dimensional scene having shadowing.
BACKGROUND OF THE INVENTION
Computers are known to include a central processing unit (“CPU”), cache memory, hard drive memory, disk drive memory, video graphics circuitry, and audio processing circuitry. The video graphics circuitry is operably coupled to a computer screen such that images, objects, and/or scenes, which the CPU processed and/or generated, may be displayed. Such images, objects, and/or scenes, are stored as a plurality of triangles, where the number of the triangles varies greatly depending on the object, image, and/or scene. For example, if a square is being presented, it could be represented by two triangles, while it may take more 20,000 triangles to represent a human face. Each of the triangles of an image has associated vertex parameters which includes RGB (red, green, blue) parameters, x, y, and z parameters, texture parameters (“STW”) and/or alpha parameters. The RGB parameters indicate the particular color of the triangle and may be an 8-bit, a 16-bit, or a 24-bit value. The x and y parameters indicate a vertex's particular location on the two-dimensional computer screen. The z parameter indicates the particular triangle's depth in relation to the screen and with other triangles. Texture parameters indicate the particular texture pattern to be assigned to the triangle and the alpha parameter indicates the translucency of the triangle.
When shadowing is being added to a scene, the particular scene is first drawn without the shadowing and stored in a frame buffer. Once the scene is drawn, the CPU and/or the video graphics circuitry determines light source projection angles and where the shadows will be cast given a particular viewing perspective. Once this is determined, a new series of triangles is created to represent the shadows, which is also stored in the frame buffer. If the shadows are relatively small in number and/or fall on simple surfaces, such as a plane, the new shadow triangles require only a small portion of memory. But, for shadows falling on complex surfaces, such as a human face, the number of new shadow triangles may far exceed the number of triangles to make up the complex surface, thus requiring a substantial amount of additional memory.
As one would expect, for a computer to process shadows falling on a complex surface, the computer would need to include a database capable of handling the worse case shadow processing, where worse case shadow processing refers to the maximum number of additional triangles that would be needed to generate the shadowing effect. For example, the triangle database may need to be four times the size of a database if shadowing were not being performed.
In addition to increasing memory requirements, the complexity of the shadow processing increases non-linearly as the number of triangles increase. As the complexity increases, dedication of the CPU to shadow processing also increases, thereby reducing the overall efficiency of the computer.
Therefore, a need exists for a method and apparatus that processes video graphics shadowing with minimal memory requirements and with minimal dedication of the CPU.
REFERENCES:
patent: 5083287 (1992-01-01), Obata et al.
patent: 5828378 (1998-10-01), Shiraishi
Fuller Richard J.
Gruber Andrew E.
ATI Technologies Inc.
Brier Jeffery
Harrison Chante′ E.
Markison & Reckamp, P.C.
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