Computer graphics processing and selective visual display system – Computer graphics processing – Graph generating
Reexamination Certificate
1997-06-27
2001-05-22
Cuchlinski, Jr., William A. (Department: 3661)
Computer graphics processing and selective visual display system
Computer graphics processing
Graph generating
C348S620000
Reexamination Certificate
active
06236405
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of computer graphics and more particularly to the generation and processing of textures in computerized graphical images.
BACKGROUND
Mapping textures onto surfaces of computer-generated objects is a technique which greatly improves the realism of their appearance. For instance, many surfaces are characterized by surface roughness which in a digitized image manifests itself in the form of local variations in brightness from one pixel to the next. Unfortunately, altering pixels in computer generated images to generate surface textures in such images imposes high computational demands and, even worse, tremendous memory bandwidth requirements on the graphics system. Tight cost constraints imposed upon the design of most products in conjunction with ever increasing user expectations make the design of a powerful texture mapping unit a difficult task.
In the present specification, we use the term “texture” as a synonym for any image or structure to be mapped onto an object, unless explicitly stated otherwise. During the rasterization process, mapping images (textures) onto objects can be considered as the problem of determining a screen pixel's projection on the image (referred to herein as the pixel's “footprint”) and computing an average value which best approximates the correct pixel color. In real-time environments, where several tens of millions of pixels per second are issued by fast rasterizing units, hardware expenses for image mapping become substantial and algorithms must therefore be chosen and adapted very carefully.
One approach is to create a set of prefiltered images, which are selected according to the level of detail (the size of the footprint), and used to interpolate the final pixel color. The most common method is to organize these maps as a mipmap as proposed by L. Williams, “
Pyramidal Parametrics”,
Proceedings of SIGGRAPH '83, Computer Graphics, vol. 17, no. 3, July 1983, pp. 1-11. In a mipmap, the original image is denoted as level 0. In level 1, each entry holds an averaged value and represents the area of 2×2 texels. As used herein the term “texel” (texture element) refers to a picture element (pixel) of the texture. This is continued until the top-level is reached, which has only one entry holding the average color of the entire texture. Thus, in a square mipmap, level n has one fourth the size of level n−1.
Mipmapping in a traditional implementation either requires a parallel memory system or sequential accesses to the texture buffer and is therefore either expensive or slow. One way to reduce data traffic is image compression. Its application to texture mapping, however, is difficult since the decompression must be done at pixel frequency.
There is accordingly a need for a texture mapping system which implements mipmapping in a rapid and/or a cost efficient manner. There is a further need for a texture mapping system which provides significant image enhancement at high rendering speeds. Moreover, particularly with respect to systems where cost is of concern, there is a need for an efficient compression scheme which reduces the amount of data required to be stored and accessed by a texture mapping system.
SUMMARY
Embodiments of the present invention advantageously enhance computer generated images by texture mapping in a rapid and efficient manner. In a principle aspect, the present invention advantageously provides a footprint assembly system which provides significant image enhancement at high rendering speeds. Embodiments employing the principles of the footprint assembly system described herein advantageously provide significant image enhancement in an efficient manner by approximating the projection of a pixel on a texture by a number N of square mipmapped texels.
In another aspect, the present invention provides a data compression system to reduce memory storage and bandwidth requirements in a simple, yet fast manner, and to therefore reduce system costs. Still other aspects of the present invention provide novel hardware architectures for texture mapping. In one embodiment, a hardware texturing unit is provided to operate on compressed textures. In certain embodiments the textures may be compressed by way of the aforementioned novel compression system. Such an embodiment advantageously decreases system cost by reducing the amount of memory storage and bandwidth required to store texture maps. In a second embodiment, a hardware texturing unit is provided to operate on uncompressed textures. Such a unit advantageously incorporates certain interpolation techniques to provide high image quality in systems where high image quality is required.
The hardware units described herein benefit from the integration of arithmetic units and large memory arrays on the same chip. This allows exploitation of the enormous transfer rates internal to a chip and provides an elegant solution to the memory access bottleneck of high-quality texture mapping. In addition to achieving higher texturing speed at lower system costs, such hardware units incorporate new functionality such as detail mapping and footprint assembly to produce higher quality images at still real-time rendering speed. Other functions which may be integrated into certain units include environment and video mapping. Such hardware units may consequently take the form of extremely versatile texturing coprocessors.
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Knittel Guenter
Schilling Andreas
Carr & Ferrell LLP
Cuchlinski Jr. William A.
Nguyen Thu
S3 Graphics Co., Ltd.
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