ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00277.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractGeometric Modellers based on a Boundary Representation scheme are well suited for display operations, but boolean operations require algorithms with quadratic complexity. Using a class of extended octtrees which is presented here, boolean operations become linear, while exact recomputation of the boundary model in the case of polyhedral objects is possible, and memory requirements are less than in classical octtree encodings. Some bounds on the memory savings are given and discussed. The DMI system, a Geometric Modeller based on a hybrid model Boundary ‐ Extended Octtrees, is presented, discussing the main operations and the interface between both models. Some modelling examples are shown. Finally, a generalization of the extended octtree encoding which allows the exact representation of objects limited by sculptured surfaces is presente

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00278.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe fill area primitive of GKS (Graphical Kernel System)1is one of the more powerful features which differentiates it from earlier device independent graphics software and systems. Its specification is extremely general in the form of a closed boundary, possibly self‐intersecting, and whose interior can be filled in a variety of styles. However a complete implementation of this primitive is very complex. It is difficult to find a single graphics workstation incorporating this primitive in hardware or firmware. Most GKS implementations will have to include software for simulating the appearance of this primitive on the commonly available displays and hard‐copy graphics devices. Correct and efficient algorithms are necessary for developing this software. Because of the generality many of the existing algorithms are not directly applicable. In this paper we describe:1. a new algorithm for clipping a fill area polygon, using what we have named as the Bridge Technique.2. implementation of a plane sweep algorithm, by Nievergelt and Preparata,2for solid filling and hatching, particularly applicable to vector devices.3. extension of the plane sweep algorithm for filling with any given pattern on raster as well as vector devices.The algorithms have been designed to work for all special cases as well. In fact they have been implemented having in mind the fill area set primitive of GKS‐3D extension.3All these algorithms have been very successfully implemented in a commercially available GKS implementation, namely in

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00279.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe GKS raster functions Fill Area and Cell Array allow area primitives in Computer Graphics to be used in a GKS environment.In implementing these functions, the computing time and memory required are important factors in deciding their usability especially for interactive work. The trend in the implementation of algorithms for such primitives is to use specialized hardware.In this paper, algorithms are introduced which are suitable for computers of low and middle efficiency and provide a sufficient image quality and an acceptable response time for dialogues.

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00280.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractA scheme is described which blurs the jagged edges of a binary picture, when it is shown on a raster display possessing a gray scale.A jagged edge is hereby defined as a one pixel discontinuity, which would result from the rounding error of vector to raster conversion.

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00281.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe purpose of any technique for modelling structures is to store a representation of them, and to produce two dimensional images such that a viewer correctly perceives the three dimensional nature of the structures. There are many methods for including three‐dimensional visual cues in a two‐dimensional image, but probably the most important one is that of shading. The intensity of light at any point on the model depends mainly on the orientation of the surface at that point with respect to the direction of the light source. In solid voxel modelling this information has to be extracted from the model. The discretisation inherent to modelling techniques has to be allowed for if successful shading is to be achieved. This paper considers the problems caused by the discretisation in solid modelling and offers compression and interpolation techniques to reduce t

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00282.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper presents the design of a novel process oriented graphics systems architecture suitable for emulating many general purpose computer graphics systems. The systems architecture has been designed loosely on the actor model of computation, and consists of a number of functionally distinct modules or processes, which communicate solely by token (message) passing. The design addresses a specific requirement for configurability and adaptability of and between modules identified within interactive computer graphics systems.

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00283.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

AbstractThe facilities of the PS‐algol programming language are described in this paper to show how they may be used to provide an integrated graphics programming environment. The persistent store mechanism and the secure transaction facilities of the language provide the basic environment in which an integrated system may be implemented. This is augmented by data types and operations to support line drawings and raster graphics. The combination of these mechanisms may be used to provide the integrated graphics programming environmen

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00284.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00285.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

ISSN:0167-7055    

DOI:10.1111/j.1467-8659.1986.tb00286.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY