Volume 08 (1989)
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Item A Transputer Network for Fast Operations on Digitised Images(Blackwell Publishing Ltd and the Eurographics Association, 1989) Arabnia, H.R.; Oliver, M.A.Algorithms for the translation and scaling of a digitised image are described. The algorithms have been designed to work on a transputer network which has a simple topology. This transputer network was originally proposed for the arbitrary rotation operation on digitised images1. The data structure used to represent the image is closely related to mnlength encoding. Both operations can be performed in real time on non trivial images.Item Calendar of Events(Blackwell Publishing Ltd and the Eurographics Association, 1989)Item A Parallel HW/SW Environment for Image Synthesis(Blackwell Publishing Ltd and the Eurographics Association, 1989) Paoluzzi, A.; Rosina, M.; Scopigno, R.AbstractIn designing graphical workstations for high-level performance presentations of graphical models, the main goal nowadays is to perform some effective real-time traversal and rendering of data. In this paper we present a reference model of parallel processing for graphics, taking into account the main aspects of colour rendering of solid hierarchical shapes- i.e., traversal of structures, hidden surfaces removal, shadow identification and light models. In particular, a parallel design of the main graphical algorithms is presented. Three abstract machines are proposed, designed respectively for data structure traversing, for depth ordering and shadows computation and finally for shape merging and screen processing. Such abstract machines, internally parallel, may be combined in various ways to define different physical architectures.CR Categories and Subject Descriptors: C.1.2 [Multiple Data Stream Architectures] MIMD Processors, Parallel Processors- 1.3.2 [Computer Graphics] Graphics Systems- 1.3.3 [Computer Graphics] Picture Generation -Display Algorithms, Viewing Algorithms- 1.3.7 [Computer Graphics] Three Dimensional Graphics and Realism - Colour, Shading, Shadowing, Visible Line/Surface I Algorithms.Item Developing an Animated Local Network Simulator(Blackwell Publishing Ltd and the Eurographics Association, 1989) Perez-Cazares, J.-R.; Rannou, R.Item The CGM Today and Tomorrow(Blackwell Publishing Ltd and the Eurographics Association, 1989) Mumford, A.M.Item Report of the Third International Conference on Computer Graphics June 22-24, 1988, Dubrovnik, Yugoslavia(Blackwell Publishing Ltd and the Eurographics Association, 1989) Suzjevic, V.Item COMPUTER GRAPHICS PROFESSIONALS(Blackwell Publishing Ltd and the Eurographics Association, 1989)Item Visualisation of Digital Terrain Data(Eurographics Association, 1989) Thiemann, Rolf; Fischer, Joachim; Haschek, Guido; Kneidl, GeraldVisualisation technology has found practical application in the field of terrain data processing. A raster data base (RDB-) concept will be introduced, i.e. a multi-dimensional concept of terrain data using elevation data, description data and/or aerial image or satellite data. Other data sources in raster or vector form may also be considered. Methods of 2- and 3-D-imaging of terrain data are pre- sented. Two-dimensional presentation will include grey- and colorcoding of different RDB layers. Techniques for superimposing two datasets are shown using relief data as one source. Color-coding, color-space transformation or a slide-effect process will be used for superimposition. The mapping of aerial image or satellite data onto the relief data will be achieved by known texture-map algorithms. The overlay technique is used for superimposing raster with vector data from geographic data bases. For superimposition, the geometry of the two datasets must not be different. Many applications need the generation of perspective views of the terrain data. For the generation a terrainraytracer will be introduced. Color impression again will be achieved by texture-mapping. Fore- and background can be handled separately. All algorithms presented are implemented in the GELA software.Item Offers to EUROGRAPHICS Members(Blackwell Publishing Ltd and the Eurographics Association, 1989)Item Colour Section(Eurographics Association, 1989) -Item Offers to EUROGRAPHICS Members(Blackwell Publishing Ltd and the Eurographics Association, 1989)Item Polygon Triangulation Algorithm as a Powerful Core Processor of PLAN-I(Blackwell Publishing Ltd and the Eurographics Association, 1989) Chen, Xiangping; Ying, DaoningA concise, complete and reliable algorithm for triangulating an arbitrary polygon is presented as a powerful core processor of PLAN-I (Production Layout Automation Nucleus) system1. A polygon with inner loops is converted into a non-self-intersecting polygon (NIP) through adding Bridge Edges . A triangular splitting algorithm for NIP is described in detail and successfully implemented. The program is about 300 lines in FORTRAN-77. Sweeping and local operations with respect to the triangular-faceted boundary representation are designed with the algorithm to improve functions of solid modeling in PLAN-I. The algorithm of triangulation can also be applied to Boolean operations and other issues.Item Accelerated Radiosity Method for Complex Environments(Eurographics Association, 1989) Xu, Hau; Peng, Qun-Sheng; Liang, You-DongAs form-factor calculation costs about 90% of the computing time when applying radiosity approach for realistic image synthesis, it is of great significance to reduce the required computation, An accelerated radiosity algorithm for general complex environments, based on environment localization and the directional form-factor concept, is presented in this paper. First we subdivide the object space into many regions. Objects contained in each region are adjacent to each other and pose more illumination effects to their neighbours. Then form-factors are calculated in each local environment,. The radiant light energy transfer between different regions is evaluated at their common boundaries. Directional form-factors are introduced to simulate the interaction of light between local environments and between non-diffuse surfaces. Comparison is made to existing algorithms. Statistic results and theoretical analysis show that the new algorithm is much faster than previous ones. The technique is especially fit for interactive design and animation sequence since modification to the shape or location of objects usually happens in local environments.Item Call for Participation in the EUROGRAPHICS WORKING GROUP on VISUALIZATION IN SCIENTIFIC COMPUTING(Blackwell Publishing Ltd and the Eurographics Association, 1989)Item Delauney Triangulations and the Radiosity Approach(Eurographics Association, 1989) Schuierer, SvenThe radiosity approach requires the subdivision of complex surfaces into simple components called patches. Since we assume to have constant intensity over a patch, the generation of regular patches is a desirable property of the subdivision algorithm. We show that constrained Delaunay triangulations produce patches that are as close to equilateral triangles as possible and thus are well suited for the partitioning of surfaces into patches. Since a number of optimal algorithms to generate constrained Delaunay triangulations have been published, the implementation presented here made use of the earlier work. The implementation consists of a rather simple modeling tool called POLY, a fast triangulation algorithm for arbitrary polygons and the form factor computation combined with a z-buffer output module.Item A Parallel Image Computer with a Distributed Frame Buffer: System Architecture and Programming(Eurographics Association, 1989) Potmesil, Michael; McMillan, Leonard; Hoffert, Eric M.; Inman, Jennifer F.; Farah, Robert L.; Howard, MarcWe describe the system architecture and the programming environment of the Pixel Machine - a parallel image computer for 2D and 3D image synthesis and analysis. The architecture of the computer is based on an array of asynchronous MIMD nodes with a parallel access to a large frame buffer. The system consists of a pipeline of pipe nodes which execute sequential algorithms and an array of m x n pixel nodes which execute parallel algorithms. A pixel node accesses every m-th pixel on every n-th scan line of a distributed frame buffer. Each processing node is based on a high-speed, floating-point programmable processor. The programmability of the computer allows all algorithms to be implemented in software. A set of mapping functions transfers image algorithms written for conventional single-processor computers to algorithms which execute in the pixel nodes and access the distributed frame buffer. The ability to use floating-point computations in pixel operations, such as antialiasing, ray tracing, and filtering, allows high-quality image generation and processing. The image computer provides up to 820 megaflops of peak processing power and 48 megabytes of memory for data-visualization applications.Item GEO++ - A System for Both Modelling and Display(Eurographics Association, 1989) Wisskirchen, PeterWe present a new concept for a graphics system which we call GEO++ . Apart from the manipulation of groups (structures in PHIGS-terminology), GEO++ permits a direct access to the tree structure required for display. With this concept we believe to have achieved a synthesis between the requirements of modelling in the sense of manipulation of building patterns and of display in the sense of editing individual objects (parts) on the screen.Item Subdivisions of Surfaces and Generalized Maps(Eurographics Association, 1989) Lienhardt, PascalThe modeling of subdivisions of surfaces is of greatest interest in Geometric Modeling (in particular for Boundary Representation) , and many works deal with the definition of models, which enable the representation of closed, orientable subdivisions of surfaces, and with the definition of elementary operations, which can be applied to these models (Euler operators) . We study in this paper the notion of 2-dimensional generalized map (or 2-G-map), which make possible the definition of the topology of any subdivision of surface, orientable or not orientable, opened or closed ; reciprocally, the topology of any subdivision of any surface may be defined by a 2-G-map . Three characteristics are associated to any 2-G-map G (the most elementary being the number of boundaries, the most known being the genus ...), and can be directly computed on G . These characteristics define the subdivision of surface modelled by G (static classification of the subdivision) . We define also operations which can be applied to 2-G-maps . Any 2-G-map (and then any subdivision of surface) can be constructed by a sequence of operations . To these operations correspond variations of the characteristics associated to the 2-G-maps . These variations enable the control of the effect of an operation on the modelled subdivision (dynamic classification of the subdivision) . The notion of 2-G-map defines the different elements of a subdivision (vertex, edge, face, bound ary...) by using one unique kind of elements, in a rigorous and unambiguous manner. Data structures may be deduced from the notion of 2-G-map . These data structures make possible the representation of any subdivision of surface , in a way near to the well-known "windged-edge" data structure defined by B. Baumgart in [BA75] . The constraints of consistency about these data structures can be directly deduced from the definition of 2-G-maps . The set of the properties of 2-G-maps (rigour, consistency, possibility of static or dynamic classification) makes the greatest interest of the 2-G-maps, with respect to other models of subdivisions of surfaces used in Geometric Modeling .Item 2.5 Dimensional Graphics Systems(Eurographics Association, 1989) Herman, IvanThe outline of an extension of traditional 2D graphics systems is given. This extension is aimed at supporting a three dimensional application program, without incorporating full viewing into the general graphics system itself. The resulting system might be very advantageous for large application programs which have their own three dimensional facilities.Item Doctoral Theses in Computer Graphics(Blackwell Publishing Ltd and the Eurographics Association, 1989) Kjelldahl, Lars