Accession Number : AD0714593

Title :   Topological Manipulation of Line Drawings Using a Pattern Description Language.

Descriptive Note : Technical rept.,

Corporate Author : OHIO STATE UNIV COLUMBUS ELECTROSCIENCE LAB

Personal Author(s) : Breeding,Kenneth J. ; Amoss,John O.

Report Date : AUG 1970

Pagination or Media Count : 39

Abstract : A large proportion of the pictures dealt with in computer graphics are line drawings. In the process of displaying these drawings certain topological manipulations such as rotations, reflections and scaling may be desired. The paper describes how such manipulations may be carried out by transformations on strings describing the pictures. The string language used is a pattern description language called PADEL. Pictures in two and three dimensional space are considered. The transformations described for two dimensional pictures are rotations, reflections about an arbitrary axis, and uniform scale changes. A nonuniform scale change consisting of scaling along an arbitrary line is also described. Such scaling may be termed 'rubber sheet warping'. The pattern description language is next extended to three dimensional objects by representing the branch labels as three tuples the element of which are the branch direction cosines. Rotations of the pictures about the coordinate axis are then described. It is then shown that the angular relationships among the branches of the picture remain invarient under this rotation. An inverse rotation is then introduced. Projections of the picture onto the principle planes is next described followed finally by projections onto arbitrary planes. (Author)

Descriptors :   (*DATA PROCESSING, *PATTERN RECOGNITION), (*COMPUTER PROGRAMMING, TRANSFORMATIONS), ALGORITHMS, PROGRAMMING LANGUAGES, TOPOLOGY, VISUAL PERCEPTION, PROJECTIVE GEOMETRY, IMAGES, ROTATION, GRAPHICS

Subject Categories : Computer Programming and Software
      Computer Hardware

Distribution Statement : APPROVED FOR PUBLIC RELEASE