Computer graphics processing and selective visual display system – Computer graphic processing system – Plural graphics processors
Reexamination Certificate
1997-10-03
2001-07-24
Zimmerman, Mark (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphic processing system
Plural graphics processors
C345S422000, C345S440000, C345S440000, C345S502000, C345S506000
Reexamination Certificate
active
06266072
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to techniques for enhancing the speed of graphics processing performed on workstations, personal computers and the like. More particularly, the invention relates to a graphics system for utilizing a plurality of rendering devices.
In a graphics system implemented by a workstation or the like, graphics processing is accelerated conventionally by a setup comprising a plurality of geometric processors for performing geometric computations in graphics, as well as a plurality of rendering processors for generating pixels. For example, a Z-merger image composition scheme involving a plurality of rendering devices to generate three-dimensional images parallel is used to increase the processing speed of “Subaru: A High-Speed High-Performance
3
D CG System” which was discussed in the autumn 1992 symposium of the Institute of Electronics, Information and Communication Engineers (proceedings, pp. 6-602-207). The disclosed system utilizes a plurality of rendering devices, each made up of a geometric processor, a rendering processor and a frame memory. On the level of pixels in which each rendering device effects its output, the system compares depth data (Z values) per pixel so that the color of each foreground pixel is selected. A final image is obtained by the system merging outputs from a plurality of rendering devices.
One advantage of the conventional technique mentioned above is that it is easy to shorten the time for image generation by simply adding more rendering devices, as discussed illustratively by Foley, van Dam, Feiner and Hughes in “Computer Graphics: Principle and Practice” (from Addison Wesley, pp. 906-907).
It should be noted that the disclosed system mentioned above with its Z-merger scheme simply selects pixels during Z value comparison and does not generate new pixel data. This means that the system has difficulty evaluating in Z values any transparent object which lets light pass therethrough. In some cases, transparent objects are not adequately displayed.
SUMMARY OF INVENTION
It is therefore an object of the present invention to overcome the above and other deficiencies of the prior art and to provide a graphics system which boosts the speed of processing on transparent objects by simply adding more rendering devices and which addresses high-performance rendering functions, such as shaded, rendering while maintaining the high-speed processing capability.
In carrying out the invention and according to one aspect thereof, there is provided a graphics system comprising: a plurality of rendering devices each including a first processor for generating rendering commands, a second processor for distributing the generated rendering commands, a frame memory for holding color, depth and weight data in increments of pixels in a screen bit map format, a third processor for executing the distributed rendering commands to write the color, depth and weight data about each pixel to the frame memory; and composition means for composing contents of the frame memories included in the rendering devices, the composition means further outputting the composed result to a display device; wherein the composition means performs arithmetic operations using depth and weight data about any one pixel position (i.e., pixels corresponding to the same X and Y coordinates) read from the frame memories of the rendering devices so as to generate new pixel data about that pixel position, the composition means further outputting the generated new pixel data to the display device.
Preferably, the composition means may be constituted by arithmetic compositors. Given a plurality of sets of color, depth and weight data about the pixels corresponding to the same X and Y coordinates from the plurality of frame memories, the compositors first compare the depth data of the multiple data sets. Regarding the figure closest to the foreground, the compositors multiply the weight and color data associated therewith; and for the next-closest figure, the compositors multiply the applicable weight and color data and add the product to that of the preceding figure, and so on. The compositors continue the product accumulation until the weight data becomes zero.
More specifically, the inventive graphics system may further comprise second frame memories for accommodating the output of the arithmetic compositors. The output of the second frame memories is used as an input to the arithmetic compositors.
As outlined and according to the invention, the arithmetic compositors in their accumulation process compare depth data one pixel at a time, multiply color data about each object, starting with the one closest to the foreground, by the corresponding weight data, and add up products from the multiplication. When the weight data include values representing transparency of objects, it is possible to compose such transparent objects on the screen.
In a setup comprising the second frame memories to hold the output of the arithmetic compositors so that the output of the second frame memories may be used as an input to the arithmetic compositors, the second frame memories amount to an accumulated frame memory arrangement for accommodating compositor outputs. This means that the number of accumulation iterations may be increased even where the number of rendering devices is limited.
REFERENCES:
patent: 5341468 (1994-08-01), Shiraishi et al.
patent: 5706415 (1998-01-01), Kelley et al.
Fujita Ryo
Katsura Koyo
Koga Kazuyoshi
Kuwana Toshiyuki
Suzuki Katsunori
Antonelli Terry Stout & Kraus LLP
Hitachi Ltd
Nguyen Kimbinh T.
Zimmerman Mark
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