6 results
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2. A Characterization of Ten Hidden-Surface Algorithms.
- Author
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Sutherland, Ivan E., Sproull, Robert F., and Schumacker, Robert A.
- Subjects
- *
SORTING (Electronic computers) , *COMPUTERS , *ALGORITHMS , *COHERENCE (Optics) , *TELEVISION scanning , *PICTURES , *OBJECT-oriented methods (Computer science) , *DATA structures , *OPTICAL computer equipment - Abstract
This paper discusses the hidden-surface problem from tile point of view of sorting. The various surfaces of an object to be shown in hidden-surface or hidden-line form must be sorted to find out which ones are visible at various places on the screen. Surfaces may be sorted by lateral position in the picture (X I'), by depth (Z), or by other criteria. The paper shows that the order of sorting and the types of sorting used form differences among the existing hidden-surface algorithms. To reduce the work of sorting, each algorithm capitalizes on some coherence property of the objects represented. ‘Scan-line coherence,’ the fact that one TV scan line of output is likely to be nearly the same as the previous TV scan line, is one commonly used kind of coherence. ‘Frame coherence,’ the fact that the entire picture does not change very much between successive frames of a motion picture can be very helpful if it is applicable. By systematically looking for additional kinds of coherence and untried sorting orders and sorting types, the paper is able to suggest two promising new approaches to the hidden-surface problem. The first, a combination of three existing algorithms, is promising because it would capitalize on both frame and scan-line coherence. The second new approach would sort in the order Y, Z, X, … the only sorting order for which an existing algorithm could not be found. [ABSTRACT FROM AUTHOR]
- Published
- 1974
- Full Text
- View/download PDF
3. Computer Processing of Line-Drawing Images.
- Author
-
Freeman, Herbert
- Subjects
- *
OPTICAL pattern recognition , *LINE drawing , *GEOMETRIC quantization , *PHOTOGRAPHS , *ENCODING , *ALGORITHMS , *APPLICATION software , *JIGSAW puzzles , *IMAGING systems - Abstract
This paper describes various forms of line drawing representation, compares different schemes of quantization, and reviews the manner in which a line drawing can be extracted from a tracing or a photographic image. The subjective aspects of a line drawing are examined. Different encoding schemes are compared, with emphasis on the so-called chain code which is convenient for highly irregular line drawings. The properties of chain-coded line drawings are derived, and algorithms are developed for analyzing line drawings to determine various geometric features. Procedures are described for rotating, expanding, and smoothing line structures, and for establishing the degree of similarity between two contours by a correlation technique. Three applications are described in detail: automatic assembly of jigsaw puzzles, map matching, and optimum two-dimensional template layout. [ABSTRACT FROM AUTHOR]
- Published
- 1974
- Full Text
- View/download PDF
4. Scan Conversion Algorithms for a Cell Organized Raster Display.
- Author
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Barrett, R. C., Jordan Jr., B. W., and Newman, W.
- Subjects
COMPUTER graphics ,FORTRAN ,ALGORITHMS ,SYSTEMS software ,COMPUTERS ,DIGITAL image processing - Abstract
Raster scan computer graphics with"real time" character generators have previously been limited to alphanumeric characters. A display has been described which extends the capabilities of this organization to include general graphics. Two fundamentally different scan conversion algorithms which have been developed to support this display are presented. One is most suitable to non- interactive applications and the other to Interactive applications. The algorithms were implemented in Fortran on the CDC6400 computer. Results obtained from the implementations show that the non interactive algorithms can significantly reduce display file storage requirements at little cost in execution time over that of a conventional raster display. The interactive algorithm can improve response time and reduce storage requirements. [ABSTRACT FROM AUTHOR]
- Published
- 1974
- Full Text
- View/download PDF
5. An Algorithm for Hidden Line Elimination.
- Author
-
Galimberti, R. and Montanari, U.
- Subjects
COMPUTER algorithms ,IBM 7040 (Computer) ,COMPUTER programming ,MATHEMATICAL analysis ,COMPUTER software ,ALGORITHMS - Abstract
The algorithm presented causes the elimination of hidden lines in the representation of a perspective view of concave and convex plane-faced objects on the picture plane. All the edges of the objects are considered sequentially, and oil planes which hide every point of an edge are found. The computing time increases roughly as the square of the number of edges. The algorithm takes advantage of reduced number of concave points and automatically recognizes if only one object with no concave points is considered. In this last case, the result is obtained in a much simpler way. [ABSTRACT FROM AUTHOR]
- Published
- 1969
- Full Text
- View/download PDF
6. An example of the use of program ''WEAK9''
- Author
-
Laslett, L
- Published
- 1974
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