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Computer Display System

IP.com Disclosure Number: IPCOM000078885D
Original Publication Date: 1973-Mar-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Appel, A: AUTHOR [+3]

Abstract

A computer system capable of generating shaded renderings of a scene for a 3D display is described. The system represents each surface in the scene as a plurality of horizontal scan lines and each scan line on a surface as a plurality of segments. One system provides specific values for illumination intensity for each surface and random value, the minimum random number value being less than or equal to lowest value illumination intensity value for any of the surfaces. As a segment of a line is considered, the illumination intensity of the surface it falls on is compared with the random number concurrently being generated. If the random number is less than illumination intensity, then the line segment is drawn, i.e., illuminated.

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Computer Display System

A computer system capable of generating shaded renderings of a scene for a 3D display is described. The system represents each surface in the scene as a plurality of horizontal scan lines and each scan line on a surface as a plurality of segments. One system provides specific values for illumination intensity for each surface and random value, the minimum random number value being less than or equal to lowest value illumination intensity value for any of the surfaces. As a segment of a line is considered, the illumination intensity of the surface it falls on is compared with the random number concurrently being generated. If the random number is less than illumination intensity, then the line segment is drawn,
i.e., illuminated. However, if the random number concurrently exceeds the generated segment's illumination intensity, then the segment is not drawn, i.e., not illuminated. In another system, each segment is provided with a value which is the sum of its orthographic or perspective projection coordinates, X and Y. If the illumination intensity of the surface on which the segment being considered currently lies falls within a chosen range of coordinate sums, and if the sums of the X and Y coordinates of the segment is an integer multiple of a function of the illumination intensity of the segment, then the segment is drawn.

For generating a shaded rendering of a scene having a plurality of surfaces, the following steps can be performed in the computer having a suitable memory:
1) a list of the vertex points of the scene is stored in the memory, 2) a topological map of the scene is stored in the memory, 3) the equations of the surfaces are computed and stored in the memory, using the list and map, 4) the equation of the lines of the scene are computed and stored in the memory, using the list and the map, 5) the directions of the normals of the surfaces such that the normals point into the volumes enclosed by the surfaces are calculated, 6) the location in Cartesian coordinates EX, EY and EZ, of the viewpoint relative to the scene is stored in the memory, 7) the perspective or orthographic projections of each point in the scene on a picture plane in Cartesian coordinates DX and DY, is calculated and stored, 8) the maximum and minimum values of the perspective or orthographic projection coordinates DYMAX and DYMIN are obtained and stored in the memory, 9) the location of the viewing light source SX, SY and SZ in Cartesian coordinates, is stored in the memory, 10) the surfaces which face away from the scene observer are determined and stored in the memory, to provide a table of potential visibility surfaces, 11) the cos...