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Interactive Computer Graphics: Flying High Part II

IP.com Disclosure Number: IPCOM000131436D
Original Publication Date: 1979-Aug-01
Included in the Prior Art Database: 2005-Nov-11
Document File: 16 page(s) / 59K

Publishing Venue

Software Patent Institute

Related People

Ware Myers: AUTHOR [+3]

Abstract

[Figure containing following caption omitted: Here are further key developments: displays that look better to the eye, higher performance in vector displays, a box that gets full speed out of electrostatic plotters, arid more.] This is the second of two parts. The first appeared last month and discussed developments in geometric modeling, color displays, and high-resolutzon black and white displays.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

This record contains textual material that is copyright ©; 1979 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Contact the IEEE Computer Society http://www.computer.org/ (714-821-8380) for copies of the complete work that was the source of this textual material and for all use beyond that as a record from the SPI Database.

Interactive Computer Graphics: Flying High Part II

Ware Myers

Computer staff

(Image Omitted: Here are further key developments: displays that look better to the eye, higher performance in vector displays, a box that gets full speed out of electrostatic plotters, arid more.)

This is the second of two parts. The first appeared last month and discussed developments in geometric modeling, color displays, and high-resolutzon black and white displays.

The appearance of resolution

If high resolution involves going to expensive technology, then clearly we need a breakthrough! In costly scientific or engineering development, such as nuclear weapons design, the price of high-resolution displays may amount to only a small proportion of the total budget, but in many workaday applications the low-cost display based on commercial television manufacturing methods is all that can be afforded.

The difficulties appear in the form of jagged edges of lines that are not vertical or horizontal, small objects appearing in one frame and disappearing in the next, moire patterns in periodic images, and loss of fine detailed The cause of these image defects is aliasing, a problem that occurs when the highest frequency in the signal being sampled exceeds one~half the sampling frequency. With each pixel in a raster scan representing a sample, the sample rate is, in effect, fixed by the television standards that set the number of pixels on the screen. Then, if fine picture detail exceeds this sampling rate, the result is picture defects. In western movies we have all seen the carriage wheels apparently revolving backwards.

The most attractive technique with which to overcome these defects -- other than actually increasing the resolution -- is, as Franklin Crow of the University of Utah puts it, "to make each sample point represent a finite area in the scene rather than an infinitesimal spot. Thus a very small object would oc cupy a part of such a small area, causing the intensity of the corresponding dot in the output image to be computed as a weighted average of the colors of the small object and its local background.''l6

Gray scale algorithms.

When a fine diagonal line crosses a horizontal scan line, it influences the two adjoining dots and sometimes three. If just one dot is turned on to full intensity, the result is the jagged effect. If two or three dots are set to the proper shades of gray, the eye perceives a smooth line, as illustrated in Crow's photographs, showing the results obtained with four algorithms.~7

To implement algorithms...