Browse Prior Art Database

Dash Generator for Digital Vector Generator

IP.com Disclosure Number: IPCOM000076189D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Chesarek, DJ: AUTHOR

Abstract

This is a dash-control system for use with a digital vector generator.

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Dash Generator for Digital Vector Generator

This is a dash-control system for use with a digital vector generator.

In graphic applications, it is frequently desirable to automatically generate dashed lines or vectors. One exemplary type of algorithm for achieving control of these dashed lines is shown in an article entitled "Algorithm For Computer Control of a Digital Plotter", by J. E. Bresenham, in IBM Systems Journal, Vol. 4, No. 1, 1965, pp. 25-30. If it is assumed that the control for the digital vector generator is by the algorithm of Bresenham, the creation of a vector is obtained by using incremental movements of the Cathode-Ray Tube (CRT) beam which are constrained to the set of plotter movements depicted by the vectors M(1)- M(8) in Fig. 1. The sequence of incremental movements for a particular vector in the first octant is shown in Fig. 2. Beam incremental motion, in the first octant, is constrained to execute M(1) or execute M(2). Vectors, not in the first octant, are generated by control based on an isomorphic mapping of the desired vector into the first octant.

In the first octant, it can be approximated that the running length of a vector L = X + 3/8 Y, where X, Y are the X and Y components of the vector, respectively. A digital vector generator, develops the vector as shown in Fig. 2. The length approximation given above will yield the current length of the vector as it is being developed, and can thus be used as the basis for controlling the dash...