Spatial models in computer-based information systems
Thomas, Adrian Lynn
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From a series of initial studies in the area of computer cartography a dual data structure was evolved based on matrix representation of graphs and the use of boolean expressions. This data structure was used principally to represent zones in space though, by using boundaries of zones, it was possible to create line networks. The original idea was to use the boolean expressions as an input language for creating volume and area descriptions and to use the graph matrices for internal manipulation and creating graphic output. However, a way was found to interpret the boolean expression directly into the form of graphic output suitable for the raster scan displays given by television monitors. The software implementation of this process was very slow but, with the current developments in integrated circuitry, it suggested a way of creating a new form of parallel display processor. This possibility was investigated initially as a general processor to carry out several related spatial operations and then, finally, merely to create displays. The applications depend on (t) the general nature of the data structure used and the possible graphic languages it makes possible and (2) the real time manipulation of displays. In the case of three-dimensional scenes, this includes an automatic hidden line and hidden area removal capability. The particular applications which have been considered include the fast access and display of maps and technical drawings from planning, archi¬ tectural and engineering data bases; the real time generation of displays for training simulation; the preparation of animated films for teaching and entertainment; the control of numerically-controlled machine tools; and solving the placement problem in computer-aided design work and overlap problems in type setting and map annotation.