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Table Look-Up Technique for Vector Generation

IP.com Disclosure Number: IPCOM000035776D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 4 page(s) / 59K

Publishing Venue

IBM

Related People

Jensen, DW: AUTHOR

Abstract

This article describes a method for rapidly drawing vectors on raster displays. Generating straight lines from a set of endpoints and storing the results in a memory map is a basic function of all advanced function displays and printers. When throughput requirements exceed reasonable software techniques, hardware is added to assist the vector generation. This article outlines the concepts of a unique table look- up technique which generates vectors faster than the conventional hardware and software approaches.

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Table Look-Up Technique for Vector Generation

This article describes a method for rapidly drawing vectors on raster displays. Generating straight lines from a set of endpoints and storing the results in a memory map is a basic function of all advanced function displays and printers. When throughput requirements exceed reasonable software techniques, hardware is added to assist the vector generation. This article outlines the concepts of a unique table look- up technique which generates vectors faster than the conventional hardware and software approaches.

Many software and hardware techniques exist which generate individual pixels or pels to be mapped into a memory representation of a screen or page to be displayed or printed. Most of these techniques supply a single pel per each iteration or step. If individual pels cannot be written into the memory map, then pels must be accumulated prior to updating the map. The described technique supplies a small image area of pels at each step. Small sections of the vector are generated in each step and can be directly merged into the memory map. Some of the desirable features of this table look-up approach for vector generation include: 1. Using predefined memory mapped small images to

replace many of the calculations used in

conventional approaches.

2. The table look-up output is compatible with

conventional memory maps; no accumulation of pel

coordinates representing individual bits into

memory map compatible data is necessary, which

eliminates intermediate steps and increases

throughput.

3. This approach is adaptable to software and

hardware implementations.

4. The concepts are adaptable to many memory map

formats.

5. The technique is independent of complexity of

pattern generation for the vectors; complex

patterns to represent the vectors can be

positioned in the same manner and speed as simple

algorithms.

Techniques used for conventional vector generation normally have software supplying individual pel coordinates at each iteration of a loop. This loop typically steps at individual pel increments in one axis direction. These individual coordinates are accumulated and then merged into the display's or printer's memory map. The accumulation may be performed to increase throughput or for compatibility with the memory map format.

Software for the table look-up method steps a large number of pels at each iteration and directly supplies small bit-mapped images for each coordinate. No accumulation is performed. All images are predefined in a permanent look-up table. The output rate for these coordinates and images typically approach the output rate for individual coordinates using conventional methods. It is possible

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to increase the output bandwidth by a factor of the stepping increment over the conventional approach of stepping through the coordinates by single increments.

The basis of this concept is that for a small bit-mapped region, there are a small, finite number of possi...