EG1990

Permanent URI for this community

https://diglib.eg.org/handle/10.2312/198

Browse

Now showing 1 - 20 of 45

Tightly-Coupled Multiprocessing for a Global Illumination Algorithm
(Eurographics Association, 1990) Drettakis, George; Fiume, Eugene; Fournier, Alain
A prevailing trend in computer graphics is the demand for increasingly realistic global illumination models and algorithms. Despite the fact that the computational power of uniprocessors is increasing, it is clear that much greater computational power is required to achieve satisfactory throughput. The obvious next step is to employ parallel processing. The advent of affordable, tightly-coupled multiprocessors makes such an approach widely available for the first time. We propose a tightly-coupled parallel decomposition of FIAT, a global illumination algorithm, based on space subdivision and power balancing, that we have recently developed. This algorithm is somewhat ambitious, and severely strains existing uniprocessor environments. We discuss techniques for reducing memory contention and maximising parallelism. We also present empirical data on the actual performance of our parallel solution. Since the model of parallel computation that we have employed is likely to persist for quite some time, our techniques are applicable to other algorithms based on space subdivision.
COLOR SHADING IN 2D SYNTHESIS
(Eurographics Association, 1990) Bourdin, J.J.; Braquelaire, J.P.
In interactive 2D synthesis applications, features for filling regions are generally elementary (uniform colouring, filling with a regular pattern.. .). Interactive design of 2D colour shadings raises two major problems: the difficulty of specifying a shading precisely, and the rapidity of related filling algorithms. In this paper, we propose a model to specify 2D colour shading of a region by decomposing it into two components: a support describing the “shape” of the shading, and a colouring function defined on this shape. We then present an incremental algorithm for support generation.
AUTOMATIC MODELLING OF NATURAL SCENES FOR GENERATING SYNTHETIC MOVIES
(Eurographics Association, 1990) Koch, Reinhard
A model based analysis by synthesis algorithm is presented. It combines image analysis and synthesis techniques to obtain a three dimensional scene description and to generate synthetic movies out of that scene description. A 3D model world is generated automatically out of TV image sequences containing 3D objects with naturally textured surfaces. The objects are projected into the 2D image domain and compared with subsequent images of the sequence to be analyzed. Differences between input and synthesized images serve to extract shape, motion and surface texture parameters and to adapt the 3D model scene. The model data base can be manipulated to generate synthetic movies with highly realistic, natural looking images.
AN INTERPOLATION METHOD FOR STOCHASTIC MODELS
(Eurographics Association, 1990) Ramstein, G.
This paper presents a method using stochastic models for the simulation and interpolation of natural phenomena. These models are based on the general concept of random functions with stationary increments, to which the fbm belongs. The consideration of this family of stochastic processes, instead of just considering the fractal one, leads to greater diversity and realism. Another way to enhance realism is to combine analysis and interpolation. We suggest calculating the stochastic parameters from the analysis of existing natural surfaces and to use them as input data for the interpolation algorithm. We propose an interpolation algorithm which respects the stochastic behavior of this class of processes. This method provides a better understanding of the interpolation mechanisms. One can thus study the influence of the stochastic parameters and the data points localization on the interpolated valued. A final advantage of this algorithm is to interpolate surfaces defined by irregular data points. This type of representation is actually often encountered in cartography (contour lines, spot elevations, ...). This possibility is also very interesting for image synthesis applications, since it allows specifying with ease the rough shape of a given image.
CHARACTERIZATION OF TOPOGRAPHIC SURFACES
(Eurographics Association, 1990) Falcidieno, Bianca; Spagnuolo, Michela
This paper presents a method for extracting and representang features of a topographic surface approximated by triangular tales An algorithm as given which computes characteristic regions (a. e. regions having concave, convex or planar shape), characteristic lanes (ridges, ravines, generic creases) and characteristic points (maxima, minima, saddle points) The result as a new surface description an terms of an attributed hypergraph representation called Characteristic Region Configuration Graph, an which characteristic regions are considered the basic describers of the surface shape and correspond to the nodes of the graph, whale the arcs and hyperarcs represent the relationships between regions derived from characteristic lanes and points
COLOR IMAGE RECONSTRUCTION FROM NONUNIFORM SPARSE SAMPLES USING A THIN PLATE MODEL
(Eurographics Association, 1990) Metaxas, Dimitris; Milios, Evangelos
In this paper we solve the problem of reconstructing a color image from sparse, noisy, and nonuniformly distributed color measurements. We apply a method for reconstructing a surface from sparse depth measurements to each of the R, G and B components of the color data, by treating each as a surface, with depth measurements being the R, G and B values. We apply this method to the reconstruction of nonuniformly distributed sparse color data from even 12.5% of the pixels, if no discontinuities are given and from 6.25% of the pixels, if the discontinuities are given. Also we present results of reconstructing a corrupted version of the original image with Gaussian noise of zero-mean and standard deviation 30 from 25% of the data, for color levels between 0 and 255. The applicability of the method is independent of the choice of the color space used.
Relaxed Multi-rate Systolic Array Graphics Engine for High Resolution Real-time Computer Graphics
(Eurographics Association, 1990) Jayasinghe, J.A.K.S.; Herrmann, O.E.
Generation of realistic images while supporting faster interaction is a topic in computer graphics research which has drawn considerable attention. Conventional frame buffer has been identified as a major bottle-neck for faster interaction [11]. Systolic Array Graphics (SAG) engines have been proposed to meet the above requirements by replacing the conventional frame buffer by a processor array. The speed limitations of the hardware restrict the use of SAG engines to displays resolutions of order 512x512 pixels when they are refreshed at 50Hz frame rate. In this paper we present an architectural solution to reduce the speed limitations of hardware. In the new architecture, a faster video stream is achieved by decoupling the speeds of the video and instruction streams by a multi-rate clocking scheme. We relax some timing constrains of the faster video stream by space domain multiplexing, i.e. using more wires.
A PROPOSAL FOR A POSTSCRIPT 3D EXTENSION
(Eurographics Association, 1990) Cesar, Christian L.
A 3D graphics extension to the PostScript language is proposed. The extension maintains the same graphic programming style that characterizes the language's 2D environment. The extensions proposed cover 3D graphics state, 3D coordinate system and transformations, and 3D path, surface and solid volume construction operators. The proposed extensions cover mostly 3D object modelling issues. Rendering extensions are not covered. Consideration is given to how the semantics of 2D graphic operators may be extended into 3D.
AN OBJECT ORIENTED APPROACH TO ENSURE PORTABILITY OF CAD STANDARD PARTS LIBRARIES
(Eurographics Association, 1990) Pierra, Guy
The integration, in CAD systems, of libraries of standard parts is often considered to be one of the key factors for increasing productivity of Computer Aided Design [1] [2] [3]. These libraries must be able to integrate homogeneously both the standard components external to the firm (standardized items and suppliers' standards) and internal firm-specific standards.
Mathematical Models for Semi-globalized Spectral Synthesis
(Eurographics Association, 1990) Anjyo, Ken-ichi
Semi-globalized spectral synthesis is proposed as a new tool for three-dimensional scene description consisting of many natural objects, such as terrain, sea waves, and clouds. The method is based on the mathematical theory of spectral representation of stochastic processes. In this paper, mathematical models in the method are presented under rigorous formulation and then their stochastic properties are shown. Some simple techniques for practical improvements of the original models in depicting scenes are also explained along with the examples obtained.
AN APPROACH TO IMPROVE THE RELIABILITY OF BOOLEAN OPERATION ON A PAIR OF POLYHEDRA
(Eurographics Association, 1990) Li, Xinyou; Sun, Jiaguang; Tang, Zesheng
It is essential and pressing to improve reliability of Boolean operations in geometric modelling systems. The Boolean operations in commercial systems now available are not reliable enough because of numerical calculation errors. Numerical calculation errors hinder us from determining set membership classifications exactly. Some classifications are ambiguous because they are dependent on adopted computing tolerance. Thereby interrelated classifications may conflict with each other and it is very difficult to get correct results of Boolean operations In many cases. We introduce a reliable Boolean operation algorithm which solves the conflicts among interrelated classifications before implementation of Boolean operation by use of reasoning technique. The algorithm has replaced the modelling module of the geometric modelling system GENS 2.0 to form a new system GENS 2.1 on Apollo and Sun workstations. According to tests and compared with Geomod 3.9 and I/ENS, GENS 2.1 is much more reliable.
Fast Rendering of Arbitrary Distributed Volume Densities
(Eurographics Association, 1990) Sakas, Georgios
In recent years a number of techniques have been developed for rendering volume effects (haze, fog, smoke, clouds, etc.). These techniques are either time consuming (ray-tracing, radiosity) or do not account for arbitrary density distributions. In this paper we briefly analyze the physics of illuminations of volumes and we propose several simplifications suitable. for computer graphics practice. In particular, we present a method for rendering arbitrary distributions by means of projective polygonal rendering and solid texturing techniques in approximately the time needed for a usual polygonal object. The proposed method provides good results in a fraction of the computing time required for approaches like ray-tracing or radiosity. Solid texturing is used to define the density distribution and a point-sampling Monte-Carlo method with user-adjustable accuracy to evaluate the illumination model along the path through the volume. Thus, a trade-off between computing time and picture quality exists. With this technique one can move through or around the volume and to place objects and/or light sources in the volume. By means of rendering methods like shadowing polyhedra, objects can cast shadows on the volume and/or the volume can shadow the ground.
3D MODELLING AND MOTION OF DEFORMABLE SOLIDS FROM 2D IMAGES
(Eurographics Association, 1990) Neveu, Marc; Faudot, Dominique
Our work purpose is to elaborate a geometric and motional model for deformable solids, known only by a very small number of general crosssections images. We start from a generic 3D model of the studied solid we distort according to detected boundaries in the above mentioned images. To give the solid motion model, our work uses moving point constraints and inbetweening methods on an image sequence : we select keyframes on which we interpolate characteristic points. Then we use Coons patches to compute the inbetween frames and realize an animation? On an echocardiographic application, we obtained good results in the model precision and detected edges by image processing similar to cardiologists' hand drawn edges. Besides, the model distortion, characteristic points tracking and 2D motion simulation are encouraging, although improvements are necessary.
TRIMO A Workstation-Based Interactive System for the Generation, Manipulation, and Display of Surfaces over Arbitrary Topological Meshes
(Eurographics Association, 1990) Slusallek, Philipp B.; Seidel, Hans-Peter
TRIMO has been designed as a workstation-based interactive system for the generation, manipulation, and display of surfaces over arbitrary toplogical meshes. In addition to rational tensor product Bezier and B-spline surfaces, TRIMO also supports piecewise rational triangular Bezier and B-patch surfaces. TRIMO has been implemented in C++ under the X Window System. Special emphasis has been given to a hierarchical data structure and to a menu-and-mouse-driven hierarchical user interface.
Hemi-Cube Ray-Tracing: A Method for Generating Soft Shadows
(Eurographics Association, 1990) Meyer, Urs
This paper presents a new ray-tracing technique for generating soft shadows. The technique treats scenes consisting of light sources and opaque objects which are polygons or polyhedra of arbitrary shape and size. To determine the intensity at a point on a surface, the hemisphere is sampled extensively through the use of hemi-cubes. So-called item-buffer boxes, a combination of itembuffers and buffer boxes, are used to calculate ray intersections as well as to suppress image aliasing. Several methods for reducing aliasing caused by hemi-cubes are discussed. The uniform treatment of rays allows for a straightforward extension of the algorithm to produce fuzzy reflections. The success of the new technique depends on a fast implementation of a visible surface algorithm as provided by today’s high-end graphics workstations. The results are images of realistically illuminated synthetic environments.
PRELOG - A SYSTEM FOR PRESENTING AND RENDERING LOGIC SPECIFICATIONS OF INTERACTIVE SYSTEMS
(Eurographics Association, 1990) Johnson, C.W.; Harrison, M.D.
Formal specifications provide the non-specialist with an extremely poor impression of what it would be like to interact with a computer system. Prototypes provide a far better impression of the ‘look and feel’ of possible implementations but lack the precision of more formal approaches. Unfortunately, specification and prototyping are typically treated as alternatives. If these two activities can be harnessed then the designer has a means of incorporating the user into systems design. Tools can ease the transition from specification to prototype by supporting the visualisation of a design in terms of graphical representations of the proposed system. This paper describes Prelog, a tool for Presenting and REndering LOGic specifications of interactive systems. Prelog supports the structured representation of interaction objects which describe virtual devices. Interaction objects support reasoning about prototypes because they provide a means of abstracting away from device dependent pragmatics which make renderings intractable.
END USER PROGRAMMING ENVIRONMENTS : INTERACTIVE PROGRAMMING-ON-EXAMPLE IN CAD PARAMETRIC DESIGN
(Eurographics Association, 1990) Girard, P.; Pierra, G.; Guittet, L.
In recent years, the number of computer end-users who do not know programming has increased rapidly. This new phenomenon has spurred a great deal of research about program design using very different approaches from the usual methods, which, as is well known, are very difficult to learn [1]. This research has touched on many programming fields : physical system simulation [2], graphical interface tailoring [3] and "macros" implementation [4] [5], data base access [6], lessons programming in Computer Aided Teaching [1] ... B.A. Myers [7] suggests a useful taxonomy for classifying these different systems. The three orthogonal criteria he uses define eight categories. A system is much more suitable for end-user programming when it is : - interactive, i.e. able to quickly echo the effect of one step of program designing, - graphic, or visual, i.e. allowing program design by commands working (at least) on a bi-dimensional environment, - associated with a running example, i.e. program designing uses values representing a running example of the program. The goal of this paper is twofold. On the one hand, it looks at a domain, rarely quoted in synthetic reviews [6] [7] [4], where these techniques are often used efficiently, and where end-user programming goes beyond the experimental phase : we are referring to parametric-design in Computer Aided Design (CAD). On the other hand, it presents a graphical interactive programming-on-examples system, named LIKE, which removes most of the problems pointed out by recent studies [7] [5].
Factoring a Homogeneous Transformation for a more Efficient Graphics Pipeline
(Eurographics Association, 1990) Abi-Ezzi, Salim S.; Wozny, Michael J.
We identify an intermediate coordinate system situated between world coordinates and display coordinates, which exhibits unique features for lighting calculations and for clipping in homogeneous coordinates. Our key contribution is an algorithm for extracting such a coordinate system from a homogeneous viewing transformation that relates WC to DC. The algorithm is based on factoring the transformation into a product of a Euclidean factor and a sparse (computationally cheap) but non- Euclidean factor. A particularly strong application of the proposed technique is the graphical processing of curved surface primitives, such as what is needed in the PHIGS PLUS viewing pipeline. Furthermore, in PHIGS PLUS the graphical data is retained by the graphics system, therefore, it is possible to perform the factoring of the viewing transformation at creation time, and to take advantage of this factored form at traversal time.
PRESENTATION OF PRODUCT MODEL DATA -AN INTERFACE BETWEEN GRAPHICS AND CAD-
(Eurographics Association, 1990) Klement, Kornel
The associative visualization of revisable product model data is of great importance for the usefulness and the acceptance of standards in the field of CAD data exchange. The outlines of a separate Presentation module which meets the resulting requirements are developed in this paper. Thereby Presentation is defined as the sum of interfacing areas between Graphics and CAD with regard to product model data visualization. The basic concepts of Presentation are introduced in a top-down approach starting with a global view on Graphics, CAD and standardization efforts in these domains. In a last refinement the linkages of product model data and graphical data primitives and attributes are examined especially those for representing product shape and annot ation information.
TRIES: DATA STRUCTURES BASED ON BINARY REPRESENTATION FOR RAY TRACING
(Eurographics Association, 1990) Thirion, Jean-Philippe
Tries are data structures used for multidimensional searching. We introduce an original method to build Tries for a set of convex polyhedra, weshow how Tries can be used for Ray tracing and we compare them with other data structures. Their advantages are mainly compactness of memory representation and fast building of the structure due to simple binary operations. Tries also accelerate the Ray tracing process compared to other octree-like structures. Furthermore, they are easy to implement because they are a unified approach to multidimensional problems. Finally we show experimental results to compare them with other data structures used for image synthesis.

Browse

Browsing EG1990 by Issue Date

Results Per Page

Sort Options