Apparatus for modifying data stored in a random access memory

Details Apparatus for modifying data stored in a random access memory Apparatus for modifying data stored in a random access memory

1988-07-28

1990-05-08

Harkcom, Gary V.

Boots, shoes, and leggings

364521, 364518, 340750, G06F 1568

Patent

active

049244159

ABSTRACT:
Input data defines the address (X,Y), and an input color (RGB) and depth (Z) for a picture element (pixel) within a stored image. In order to perform hidden-surface removal (HSR), current depth values are stored for each pixel and compared with the input depth value to determine whether or not input data should be written to define a new color and depth for the pixel at (X,Y). The color and depth values are stored in a color RAM (9) and z-RAM (64). To obtain a speed advantage when modifying a series of consecutive pixels and one row of the RAMs, the current depth values are read and compared in advance for each pixel, during the writing period of one or more preceding pixels. The apparatus comprises a control and arithmetic unit (42), and a HSR control circuit (60) in addition to the color RAM (9) and z-RAM (64). The apparatus uses readily available video DRAM chips to provide a z-RAM with two data ports (62,66). The apparatus may form part of an electronic graphics system.

REFERENCES:
patent: 4609993 (1986-09-01), Shimizu
patent: 4625289 (1986-11-01), Rockwood
patent: 4748572 (1988-05-01), Latham
A. Masahide Ohhashi et al., "THPM 12.7: A 32b 3-D Graphic Processor Chip with 10M Pixels/s Gouraud Shading", ISSCC 88 (2/18/88), 1988 IEEE International Solid-State Circuits Conference, pp. 168-169.
Newman & Sproull, Principles of Interactive Computer Graphics, pp. 369-371 McGraw-Hill, 1979.

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