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Computer Graphics Using Multi Echelon Processing Structures

IP.com Disclosure Number: IPCOM000051505D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 9 page(s) / 138K

Publishing Venue

IBM

Related People

Boinodiris, S: AUTHOR

Abstract

Developed methodology for mapping a program onto multi-echelon processing structures is applied specifically on the problem of interactive computer graphics. The versatility of multi-echelon structured processing allows an independently segmented, nested program, such as a graphical sorting process, to be mapped directly onto corresponding hardware resource assemblies. The large degree of parallelism within a multi-echelon structure is shown to be optimizable with respect to the allocated graphical processing resources, combining parallelism with pipelining formed by each echelon.

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Computer Graphics Using Multi Echelon Processing Structures

Developed methodology for mapping a program onto multi-echelon processing structures is applied specifically on the problem of interactive computer graphics. The versatility of multi-echelon structured processing allows an independently segmented, nested program, such as a graphical sorting process, to be mapped directly onto corresponding hardware resource assemblies. The large degree of parallelism within a multi-echelon structure is shown to be optimizable with respect to the allocated graphical processing resources, combining parallelism with pipelining formed by each echelon.

Recent advances in computer graphics produced a remarkable improvement in scene realism. This article utilizes these algorithms in a mapping methodology specifically constructed for parallel multi-echelon processing structures. This methodology is geared to enhance the speed of these algorithms through parallel processing, without losing any scene realism.

Graphical studies categorize shaded display into two basic approaches. The first approach calculates visibility and shade at sample points on the surface, and interpolates between these points. For surfaces constructed of planar polygons, this approach produces exact images. The second approach calculates visibility and shade for all points of the surface. This approach is applied mainly to curved surface display, since data interpolation for such surfaces does not produce an exact image. The second approach is usually slow, a disadvantage which led some users to approximate curved surfaces with collections of polygons in order to gain speed. The use of "smooth shading" with polygonal surfaces results in a reasonable approximation.

One of the most widely known procedures, the Watkins' algorithm, displays polygon surfaces in scan line order. It has a hierarchical object description where each object subdivides into polygons, each polygon into edges, and each edge into vertices. Each vertex module contains the x, y, and z coordinates of the polygon vertex in image space. Pointers link the edges into lists of a multi- echelon structural decomposition. The sorted primitives of the Watkins' algorithm
[1] are polygons.

A modification to Watkins' algorithm was originated by Gouraud [2], who described an algorithm producing a remarkable improvement in realism for curved surfaces approximated by polygons. This algorithm, instead of assigning a single shade value for the entire polygon, stores an intensity value for each polygon vertex.

The algorithm first to display bicubic patches was Catmull's
[3]. This algorithm basically takes each patch and repetitively subdivides it until each of the resulting subpatches covers, at most, one raster element. At this point of subdivision, each subpatch can be utilized as a polygon. The shade value of each subpatch-representing polygon is evaluated and assigned to the raster element of its position. Patches are proc...