http://graphics.cs.msu.su
February 14 - 18, 1995
******************** V O L U M E I **************************
GENERATING A MODEL OF PLANT USING NURBS
Bedrich Benes
CTU, Fac.of Electrical Eng., Dept. of Computer Science
Karlovo nam.13, 131 25 Prague, Czech Rep.
e-mail benes@sgi.felk.cvut.cz
Abstract is not available.
Keywords: Computer Graphics, NURBS, Modelling
ONE METHOD OF THE HUMAN BODY MODEL ANIMATION
R. Berka, I. Jelinek
Department of Computers
Faculty of Electrical Engineering
Czech Technical University
Karlovo nam. 13
121 35 Prague
Czech Republic
e-mail: berka@cs.felk.cvut.cz
jelinek@cslab.felk.cvut.cz
In the first part of the paper we show a new approach to the
modelling of the human body. The modelling of the human body
has two parts - the model structure description (the model of
the human body we call "figure") and the model motion control.
The second part of this article is devoted to methods of the
figure's structure formal description and to control of the
figure's behavior. For this purpose we have proposed a
special formal language FDL (Figure Description Language).
The next part informs on the implementation our ideas in
program VITALIATOR. The implementation is consistently based
on the object oriented approach. In the last part of our
contribution we discuss questions connected with control of
all actor's body parts and parallel movement control of more
figures.
Keywords : computer animation, object-oriented graphics,
human body animation, modelling
AN APPROACH TO DRAWING FAIR PLANE OPEN CURVES
Marcelo Cordeiro Bernardes, Wu Shin-Ting,
Itala M.L.D'Ottaviano
DCA - FEE - UNICAMP, CLE/IFCH - UNICAMP
e-mail: {ting,mcb}@dca.fee.unicamp.br
itala@cle.unicamp.br
In this paper an approach for interpolating a given sequence
of points by a fair plane curve is presented. Since the
fairness concept is subjective, a non classical modelling
tool - fuzzy sets - is used and interactive facillities are
provided. Some results of our implementation are included.
A PARALLEL APPROACH TO HIERARCHICAL RADIOSITY
Christian A. Bohn, Robert Garmann
German National Research Center for Computer Science
Dept. Visualization and Media Systems design
Sankt Augustin, Germany
e-mail : bohn@viswiz.gmd.de,
garmann@ls7.informatik.uni-dortmund.de
A parallel algorithm solving the radiosity equation is
presented. It is based on the hierarchical approach (HR) [5]
and realized on a massively parallel supercomputer - the
Connection Machine 5.
Our algorithm considers the HR approach as a process
that manipulates a huge graph structure. Simulated annealing
is used in the graph's rearranging procedure to achieve
a good work-ballance and nearly optimal communication costs.
The implementation shows a significant step to
faciliate the aplication of a radiosity solver, produced on
one hand by the few user-support that HR needs, on the other
hand by the fast calculation times the parallel
implementation offers. On 64 processors we obtained a speed-up
of 8.4.
Keywords : Computer Graphics, Scientific Visualisation,
Hierarchical radiosity, Rendering, Simulation,
Parallelization, Message Passing, Supercomputer,
Architecture.
FAST COLOUR SHADING
J.J.Bourdin
Departement d'Informatique
Universite Paris-8
2,rue de la Liberte
935 26 Saint-Denis 02 - France
e-mail: jj@aristote.univ-paris8.fr
Colour shading a region of the plane is the action of filling
its interior with continuously varying colours. Some classic
methods are presented. This paper proposes an original
approach to colour shading. A condition of smoothness is
given. A region is modeled as a support and a chromatic
function. Various shapes of shading are presented.
Incremental computing and benchmarks are also discussed. In
addition, we solve the problem of good visual smoothing for
an angular colour shading.
Keywords : Shading, colour shading, 2D Graphics, Computer
graphics, fundamental algorithms
STUDY OF ITERATIVE PROCESSES IN COMPUTER GRAPHIC'S PROBLEMS
Jean-Marc Brun, Sebti Foufou, Abdelaziz Bouraz,
Philippe Arthaud
LISPI /LIGIA bat.710
Universite Claude Bernard LYON 1
43 Bd du 11 Novembre 1918
69 622 Villeurbanne Cedex
Coretech International
27-29, Bd du 11 Novembre 1918 B.P. 2131
69 622 Villeurbanne Cedex
The convergency of iterative processes can exhibit unexpected
behaviour. In this paper an analysis of the convergency of
the iterative processes is made through the aplication of the
Newton method to the polynomial equations resolution. This
leads to the definition of a dynamic relaxation scheme
applied to computer graphics.
Keywords : Iterative processes, convergency, relaxation,
equations, graphics.
THE INTERACTION OF THEORY AND PROCEDURE IN FRACTAL GEOMETRY
Stephan D. Casey
Department of Mathematics and Statistics
The American University
4400 Masachusetts Ave., N.W.
Washington, D.C. 20016-8050
e-mail:scasey@american.edu
This article discusses the interplay in fractal geometry
occuring between computer programs for developing
(approximation of) fractal sets and the underlying dimension
theory. The computer is ideally suited to implement the
recursive algorithms needed to create these sets, thus giving
us a laboratory for studying fractals and their corresponding
dimensions. Moreover, this interaction between theory and
procedure goes both ways. Dimension theory can be used to
classify and understand fractal sets. This allows us, given
a fixed generating pattern, to describe the resultant images
produced by various programs. We will also tie these two
perspoectives in with the history of the subject. Three
examples of fractal sets developed around the turn of the
century are introduced and studied from both classical and
modern viewpoints. Then, definitions and sample calculations
of fractal and Hausdorff-Besicovitch dimensions are given.
Finally, dimension theory is used to clasify images.
TEXTURE, DISPLACEMENT AND IMMERSION : A MODEL FOR TREE
RENDERING
Miguel Chover, Roberto Vivo, Ricardo Quiros, Xavier LLuch
Departamento de Informatica, Universidad Jaume I.
Campus de Penyeta Roja, 12071 Castellon, España
Tel. ++34 64 345771, fax ++34 64 344858
e-mail chover@inf.uji.es
Departamento de Sistemas Informaticos y Computacion
Universidad Politecnica. Camino de Vera s/n
46071 Valencia, España
This paper presents a new method to generate realistic
details on tree surfaces and structures. The method combines
texture, displacement and immersion techniques. We use
an extension of L-systems, namely random L-Systems, to
construct the tree, and represent its structure of branches
using parametric surfaces (cones). Adding displacement at the
surface level by means of 2D and 3D functions, and deviation
at the structure level by immersion in a 3D function, we
perturb the surface definition. The parametric definition of
the surface is adequate to apply textures and reduces the
spatial cost of the previous tree representations. In
addition, the proposed technique can even manage further
detail than previous ones.
DYNAMIC SUBDIVISION IN RADIOSITY
Eric Dubuis, Hanspeter Bieri
Institut fur Informatik und angewandte Mathematik
Universitat Bern, Langgasstrasse 51, 3012 Bern, Switzerland
e-mail dubuis@iam.unibe.ch, bieri@iam.unibe.ch
This paper presents a fast radiosity algorithm for
illuminating scenes containig large piecewise polygonal
surfaces. Dynamic subdivision is based on the well known
Adaptive Subdivision, introduced by M.Cohen et.al.[3]. During
the illuminating process, patches in areas with high
intensity gradients are refined. Contrary to Adaptive
Subdivision, the presented algorithm subdivides patches not
in a static way. The patch hierarchy is dynamic and adapted
to the respective state of the illumination process. To take
a decision concerning path subdivision, more information
about the gathered energy of a patch is considered than with
Adaptive Subdivision. The results show that this new
algorithm can lead to remarkable speedups compared to
Adaptive Subdivision.
SPEEDING UP PROGRESIVE RADIOSITY BY OVERSHOOTING
Martin Feda
Technical University of Vienna
Institute of Computer Graphics
Karlsplatz 13/186-2
Vienna, Austria
e-mail feda@cg.tuwien.ac.at
Overshooting techniques have proven to significantly speed up
the convergence of radiosity computation. Similar methods
(overrelaxation) have also been widely used in numerical
mathematics to speed up iterative solution methods for linear
equation systems, e.g. Gauss-Seidel iteration. This paper
gives a comprehensive description of all overshooting
techniques. Advantages and disadvantages of the different
techniques are also described.
ATTRACT - ITERATIVE VISUALIZATION OF DYNAMICAL SYSTEMS
Eduard Gröller, Herbert Oppolzer
Technical University Vienna
Institute of Computergraphics
Karlsplatz 13/186/2
A-1040 Vienna, Austria
Tel.+43(1)58801-4582
FAX +43(1)5874932
e-mail groeller@cg.tuwien.ac.at
herbert@cybercafe.co.at
An interactive program for visualizing the long term behavior
of dynamical systems, e.g., attractors and bifurcation
diagrams is presented. The program allows an easy
specifications of a set of formulas and constants which
describe a dynamical system. This set of equations is then
used for displaying the geometrical structure of the long
term development of dynamical system. The user defines the
assignment of variables of the dynamical system to at most
three spatial axes and one colour axis. Viewing parameters,
e.g., point of view, zoom, rotation angle, can again be
changed interactivelly. The program is intended to provide
researchers working on dynamical systems with a fast visual
analusis and experimentation tool.
Keywords : visualization, dynamical system, interactivity,
attractor, bifurcation diagram.
COMBINING CLUSTER ANALYSIS AND CONTINUOUS ISOSURFACE
COLOURING IN A TOOL FOR DATA EXPLORATION
Johan Hangman
SSKKII, University of Göteborg
41298 Göteborg, Sweden
e-mail hagman@ling.gu.se
The paper shows how two powerfull techniques for supporting
data exploration of multidimensional data can be combined in
a tool for this purpose. The techniques, cluster analysis and
graphics visualization, are briefly presented and discussed
as modules of a prototype. Its preformance is illustrated by
experiments resulting in cluster configurations where the
value distribution of "underlying" dimensions are visualized
with colors or shades of grey.
NON-PHOTOREALISTIC SHAPE CUES FOR VISUALIZATION
Peter Hall
Department of Computer Science
PO Box 600
Victoria University of Wellington
New Zealand
e-mail peter@comp.vuw.ac.nz
Visualization applications often need to display objects that
are both three dimensional and coloured. The objects may be
represented either by surfaces or by volumes. The motivation
behind such displays is to demonstrate two or more
independent variables at once. So one variable may determine
object shape and anotehr variable may determine the
distribution of colour. A lighting model is needed to provide
cues for visual shape recognition. Conventional lighting
models provide these cues by altering colour. Hence
a conflict arises when this approach is adopted because the
total color variation is made up of two components that are
perceptually indistinguishable. There are variations that
show the distribution of a variable, and global variations
caused by the lighting model. It might be said that a side
effect of the light model is to distort the information
represented by colour.
This paper offers a solution to this problem be
replacing the conventional lighting model with a structured
lighting model of the kind used in machine vision context.
The proposed solution simulates the shadow of a regular,
planar grid on the surface of an object. Improved shape cues
can be obtained by using a grid that is sensitive to lighting
conditions, this generates a cross-hatch shading effect. The
notion of a planar grid easily generalises to three
dimensions, where it can be used not only with surfaces, but
also with volumes. The benefit of the method is that colour
is effected only locally, and in well defined places; the
remaining colour is readily identifable and faithfully
represents underlying data. In addition, the method in either
of its forms is simple to incorporate into existing
renderers.
The method is demonstrated with results obtained from
a computation fluid dynamics application. Both coloured
iso-surfaces and coloured volumes are shown.
ADVANCED DESIGN SOFTWARE FOR THE INJECTION MOULDS DESIGN
BASED ON SOLID MODELLING TECHNIQUES
Ir. T. S. Huang
Division of Production engineering,
Machine design and Automation
Faculty of Engineering, Department of Mechanical Engineering
Katholieke Universiteit Leuven
Celestijnenlaan 300B
B-3001 Heverlee Belgium
This paper describes a CAD software that focuces on
computer-aided design for injection moulds using solid
modelling techniques. The ultimate goal of this CAD software
is to enable the designer to do various mould design works.
It consists of two main modules, geoetric modelling and mould
design. The former consists of a set of functions which can
be used to create solid primitives and execute Boolean
operations and the latter is able to support the design of
standard mould components and some further applications such
as the automatic determination of undercut, parting lines and
parting surfaces, core and cavity plates, etc. This software
is now implemental on a Unigraphics CAD/CAM system and
operated in a dialogue mode to communicate with the user.
Keywords : Solid modelling, three-dimensional convex hull,
Injection moulds, Undercuts, Parting lines and parting
surfaces.
OPTIMIZING PATH TRACKING USING NOISE REDUCTION FILTERS
Henrik Wann Jensen, Niels Joergen Christensen
Dept. of Graphical Communication
Technical University of Denmark
fax : +45 45 93 83 17 phone : + 45 45 93 41 66
e-mail : igkhwj@unidhp.uni-c.dk, igkncj@unidph.uni-c.dk
The problem of global illumination can be solved using path
tracing. Unfortunatelly path tracing gives very noisy images.
This noise is mostly caused by the indirect illumination
reflected diffusely. The common way to reduce the noise is
to use more samples/rays per pixel. However, tho convergence
speed in path tracing makes this strategy very costly. In
this paper we propose a technique in which light reflected
diffusely two times is separated from the final solutin. This
light is filtered by different noise reduction filters and
then added to the remaining solution. In this way we avoid
blurring the image and at the same time we are able to reduce
the noise level significantly.
Keywords : Global illumination, path tracing, noise reduction,
filtering.
GRAPHSUPPORT : INTERACTIVE MODELLING WITH COMPUTER GRAPHICS
IN ASSISTING DESIGN
Ö. Karaçali
University of Technology, Loughborough, England
e-mail O.karacali@lut.ac.uk
This paper explains a novel approach that the dsesigner can
be supported by interactive object modifications with
graphics system. An engineering application, called
GraphSupport system is identified and relations to the
software support aspect is discussed. An example of
industrial product in interactive modelling with objects is
applied to GraphSupport to aid engineering design. Simple,
yet versatile, information and functional modelling methods
are introduced , allowing variants and views of the product
to be represented and modified in a solid modelling
environment.
EFFICIENT FILTER COMPUTATIONS WITH SYMMETRIC MATRIX KERNELS
Manfred Kopp
Institute of Computer Graphics, Visualization and Animation Group
Technical University of Vienna
Karlsplatz 13/186-2, A-1040 Wien
e-mail m.kopp@ieee.org, http://www.cg.tuwien.ac.at/~kopp/
This paper presents an algorithm for filter calculations using
symmetric matrix kernels. This algorithm outperforms
traditional methods for kernels larger than or equal to 5x5
on machines based on RISC designs, where the time needed to
calculate an adittion equals the time needed for
multiplication. The algorithm is based on a decomposition of
the kernel matrix into several kernel matrices of decreasing
size, which can be computed very fast because of
spatial coherence. A comparison with traditional methods
shows the efficiency of the presented approach.
Keywords : image processing, anti-aliasing, filtering,
symmetric matrix kernels, spatial coherence.
PARAMETRIZING SUPERQUADRICS
Helwig Löffelmann, Eduard Gröller
Institute of Computer Graphics
Technical University of Vienna
A-1040 Karlsplatz 13/186/2
Superquadrics are well known and often used 3D surface
objects in computer graphics. They are used for modelling
parts of scenes that are then rendered using photorealistic
synthesis algorithms (e.g., ray tracing) . For some
techniques, like texturing, which are part of these rendering
methods, the type of the parametrization of such a surface
has to be chosen carefully and is not intuitively obvious at
first sight. There are cases, where the straightforward
extension of quadric parametrizations to superquadrics do not
produce satisfying results. We therefore investigate a number
of different parametrizations in combination with the
corresponding formulas, and point out some significant
differences between them.
Keywords : Conics, Superconics, Quadrics, Superquadrics,
Parametrizations
TOPOLOGICAL OPERATIONS FOR NON-MANIFOLD MODELING
David Marcheix, Stefka Gueorguieva
Processing non-manifold topologies (abbreviated as NMT) plays
a primary role in current development of solid modelling
applications. Euler operators are a powerfull tool for
creation of valid boundary representations of solids. By
contrast with the manifold domain, where topological
operators are well understood and implemented, there is a
lack of elaboration of their non-manifold counterparts.
In this paper we work out a basis of Euler-like
operators for construction, maintenance and manipulation of
boundary schemes of non-manifold objects. The presented
algorithms are implemented for a NMT data structure and
experimental results are discussed in the context of the
completeness and soudness of the NMT operators.
Keywords : geometric modelling, non-manifold topology,
boundary representation, Euler operators, data structures,
algorithms.
AN AVERAGE-CASE COMPLEXITY OF RAY TRACING ALGORITHMS
Gabor Marton, Laszlo Szirmay-Kalos
Department of Process Control
Technical University of Budapest
Budapest, Müegyetem rkp.9/R, H-1111, Hungary
e-mail marton@seeger.fsz.bme.hu
A theoretical framework for analyzing average-case time and
storage complexity of ray tracing acceleration techniques
is introduced by means of homogeneous spatial Poisson point
processes. Then, as a demonstrative example of its
application, the expected query time of the widely known
techique based on a regular spatial grid is analyzed. Finally,
an interpretation of the results is presented within the
context of probability theory.
USER-COMPUTER INTERACTION : COGNITIVE PROPERTIES OF ICONS
FOR MULTIDIMENSIONAL DATA ANALYSIS
Antonio Messina, Laura Moltedo, Silvana Contento,
Roberto Nicoletti
Dipartimento di Fisica "A.Righi", Universita di Bologna
Instituto per le Applicazioni del Calcolo "M.Picone" , Roma
Dipartimento di Psicologia, Universita di Bologna
Dipartimento di Scienze Biomediche, Universita di Modena
Italy
In the graphical environment, icons (i.e. symbols or
pictorial representations analogous to physical objects,
actions or functions) are generally more informative and
easier to manipulate than verbal labels. Because icon should
resemble the functions they represent, pre-testing should be
done to determine whether the user understands what the icons
are supposed to symbolize. In the present work we aimed at
establishing whether the criteria adopted to shape the icons
of a graphic tool for the analysis of multidimensional field
(MUDI3) were shared by the user. Method, procedure and
results are presented and discussed.
ON SCENE COMPLEXITY DEFINITION FOR RENDERING
Ludovit Niepel, Jozef Martinka, Andrej Ferko, Pavol Eliass
Department of Computer Graphics and Image processing
Comenius University, 842 15 Bratislava, Slovakia
e-mail niepel, ferko, elias@fmph.uniba.sk
Jozef.Martinka@st.fmph.uniba.sk
This paper introduces one way how to define mathematically
correct way the complexity of the polygonal scene for
rendering. This complexity allows to compare previously
uncomparable rendering algorithms via computing the
complexity of various scenes, and give the more rigid
solution of other related problems. The advantages of this
unified approach are discussed.
PARALLEL ADAPTIVE RAY_TRACING
Irena Notkin, Craig Gotsman
Department of Computer Science
Technion - Israel Institute of Technology
Haifa 32000, Israel
e-mail {cyrus|gotsman}@cs.technion.ac.il
We describe a dynamic task allocation algorithm for ray
tracing by adaptive progressive refinement on a parallel
computer. Parallelization of adaptive ray tracing is
difficult because of the inherent sequential nature of
the sample location generation process, which is optimized
(and different) for any given scene. We report on
experimental results obtained from our implementation of
this algorithm on a Meiko parallel computer. The three
performance measures of the algorithm, namely, load-balance,
speedup, and image quality, are shown to be good.
TUNNING RENDERED LINE-DRAWINGS
Bernhard Preim, Thomas Strothotte
e-mail {bernhard|tstr}@isg,cs.uni-magdeburg.de
Normally rendered imagesare the polished output of rendering
software and are, by definition, "perfect". However, as we
think about rendering abstractions of the underlying models,
rather than photorealistic images, it becomes evident that
user involvement is necessary to tune the rendered images to
his or her satisfaction.
In this paper we outline methods to tune rendered
images. We concentrate on-line drawings, as these are most
readily edited to make the modelled object appear more
abstract. Rather than having user edit individual lines, our
emphasis lies on studying, what users really want to achieve,
and how we can support them more directly to attain these
effects. This emphasis is used to guide the design of the
user-interface to the system for tuning line-drawings.
We present a tool which allows high-level
intent-based interaction to generate line-drawings from
rendered 3D-models. Included in the system are editting
facilities to fine-tune and thereby individualizing
line-drawings. High-level interaction draws on statistical
methods to distribute over the rendered image. We show how
the interaction can be improved if information about the
model is available to the image editor.
Keywords : Non-photorealistic images, line-drawings,
architectual sketches, human-computer interaction.
PHOTO-REALISTIC GRAPHICS FOR EMERGENCY LIGHTING VISUALISATION
Thomas Ramstad, Alan Chalmers
Department of Computer Science
University of Bristol
Bristol, BS8 1TR
United Kingdom
In an emergency situation it is vital that people are rapidly
able to identify the exits. This is particularly important
when the visibility of the sign can be significantly reduced,
for example in a smoke filled room. There are several factors
which contribute to a sign's visibility : the colour of the
sign, luminance, size of letters, the location of the sign in
the room and of course how engulfed the room is with smoke.
It is also important to determine the visibility in clear and
dark conditions. This paper describes a visualisation system
under development which uses photo-realistic computer
graphics techniques and parallel processing to provide an
interactive tool for emergency lighting designers. The system
will enable designers to investigate different positioning
and illumination of emergency lighting under a variety of
environmental conditions.
VISUALIZATION OF SMOOTHED PARTICLE HYDRODYNAMICS
Rene T. Rau
WSI/GRIS, Universität Tübingen
Auf der Morgenstelle 10
D-72076 Tübingen, Germany
Today smoothed particle hydrodynamics (SPH) play an important
role in the computation of gas dynamical processes appearing
in astrophysics and other fields. Nevertheless the
visualisation techniques for this particle based model are
still rudimentary. In order to visualize the density and
pressure appearing in the simulation correctly we
investigated the simulation in more detail. By this
investigation we show that a splatting based visualization
technique displays the volume density and pressure used in
the simulation exactly. Furthermore we conclude that in our
situation splatting is the only reasonable technique and is
superior to other techniques such as raycasting. Finally, our
visualization method enables the scientist to control the
result of the simulation especially with few particles and
gives high quality rendering at every state of the research
process.
******************** V O L U M E II **************************
MULTIMEDIA INTERFACE FOR ADVANCED MATHEMATICS:
OTTER 3.0 AS A CASE STUDY
John F. Richardson
NCCOSC
Code 44201
53560 Hull Street
San Diego, Ca. 92152
United States
e-mail richards@marlin. nosc.mil
This paper describes a multimedia interface for the OTTER
theorem proving system. This interface is implemented using
an advanced multimedia authoring system based upon the
SUPERCARD program. SUPERCARD is a Hypercard type system that
basically solves most of the problems prevoiusly existing in
Hypercard. This interface described in this paper is designed
for the Macintosh computer although multimedia authoring
systems exist for Unix and PC based systems.
The primary purpose of this interface is to provide
a "Macintosh look and feel" environment for the OTTER theorem
proving system. The interface provides this look and feel
through the use of hypermedia objects called cards. These
cards serve as backdrops for interactive graphics and
controls made available to the user for interacting with the
theorem power.
The secondary purpose of the interface is to
provide a natural environment for navigating within the
theoretical realms of Automated Reasoning, Logic Programming,
Theorem proving and mathematics. The interface seeks to
restructure the rules and symbols of the above realms into
more "user friendly" and "intuitive" rules and symbols for
use by students and general mathematicians. The interface
also seeks to make it easier on experts in the field of
Automatic theorem proving.
Keywords : Multimedia, Automatic Theorem Proving,
Expert Systems, Animation, Hypermedia
FLOW VISUALIZER
Harald Ruckser
Institut für Informatik
Abteilung für graphishe und parallele Datenverarbeitung
Universität Linz, Altenbergerstrasse 69, 4040 Linz
Austria
In this paper a new system for visualization of combined
scalar and vector fields is presented. The methods
implemented in this system are based on the use of
combination AVOs (abstract visualization objects) consisting
of arrows, spheres, isosurfaces, streamlines and cylinders.
These AVOs improve the understanding of correlations between
the spatial distributions of one vector and up to three
scalar quantities, and enable simple forms of topological
filtering. Furthermore, new clasification methods for
visualization methods and AVOs are introduced, which, among
others, describe the dimensionality of the data that a single
AVO displays (DD - displayed dimensions). An extended model
of the visualization process reveals important details of the
microstructure of visualization, its transformational phases
and objects.
AN ARCHITECTURE OF MULTIMEDIA PLATFORM FOR INTEGRATED
AUDIO-VISUAL DATA PROCESSING
Ok-Keun Shin*, Hyun-Ki Kim and Young-Do Chae
Electronics and Telecommunications Research Institute
Korea
(* e-mail okshin@kiet.etri.re.kr)
In this paper, we introduce an experimental hardware
architecture of a multimedia data processing system called
ComBiStation, whose applications area includes multimedia
authoring, CSCW and video conferencing. The platform
comprises most commonly needed multimedia processing
functions: audio-visual data capture, playback, multistandard
compression as well as interleaving of compressed audio
visual data. The proposed architecture minimizes the CPU
overhead that might be caused by multimedia data processing
and assures the fluent data flow among system components. We
begin with overall architecture of the whole system, and then
audio-visual data capture/display unit and multistandard
compression unit are discussed. Implementation issues and
future works are also discussed.
Keywords : Multimedia Platform, Compression, CSCW, Video
Conferencing
DITHERING AS A METHOD FOR IMAGE DATA COMPRESSION
Pavel Slavik, Jan Prikryl
e-mail slavik@cslab.felk.cvut.cz, prikryl@sgi.felk.cvut.cz
Abstract is not available.
Keywords : data compression, dithering, parallel processing
ASPECT GRAPHS OF THREE_DIMENSIONAL SCENES
Eduard Sojka
Department of Computer Science
Technical University of Ostrava
ul.17.listopadu, 708 33 Ostrava-Poruba
Czech Republic
e-mail eduard.sojka@vsb.cz
The paper presentes a new approach to the theory of aspect
graphs. This approach is based on the presumption that an
equivalence relation can be introduced on the set of images
of a given scene. The equivalence relation induces the
decomposition of the set of images, which is infinite, into
the finite number of classes. Similarly, also the space
surrounding the scene is decomposed into the classes. From
every point of certain class, equivalent images of the scene
are perceived. The aspect graph is the graph that contains
the information about these classes and the relations between
them. Presented theory enables to put the approaches
published earlier into the unifying framework. The paper also
presents an example in which the general theory of aspect
graphs is applied to the three-dimensional problem. Also an
algorithm for computing the decomposition of space into the
classes is proposed.
Keywords : Aspect graph, visual potential graph, visibility
DISCRETE RAY TRACING HIGH RESOLUTION 3D GRIDS
Nilo Stolte, Rene Caubet
Institut de Recherche en Informatique de Toulouse
118, Route de Narbonne
31062 - Toulouse - France
e-mail stolte@irit.fr
This article suggests a new approach to discrete Ray-Tracing
in which a two step three-dimensional DDA and an octree are
used. A very important problem regarding this kind of
Ray Tracing, also known as Raster Ray Tracing, is the amount
of memory required to store the 3D raster grid which will
contain the discretized scene to be visualized. Since the
resolutin of this grid is huge because the voxel is assumed
to be approximatelly the size of a pixel on the screen, it is l
imited by the maximum amount of memory of today's machines.
Although using an octree and assuming that the majority of
space will be empty, as such is the case in most scenes,
an important memory saving is achieved. This memory saving
helps using discrete Ray Tracing in normal workstations. It
is shown that the special octree presented here doesn't slow
down Ray Tracing significantly and even competes with normal
discrete Ray-Tracing. It is also shown that in critical cases
this octree will not occupy much more space than a normal
3D grid.
Another important problem is the bottleneck caused by
the three dimensional DDA in such huge resolution grids. This
problem is solved by dividing these grids into two low
resolution ones. The process can be divided in two steps
where optimal times of three-dimensional DDA are achieved.
This is shown through the comparative tests with the single
step process.
Keywords : Ray-Tracing, Discrete Ray_tracing,
Raster Ray-Tracing, Octree, Three-dimensional DDA, Voxel
ON CONVERGENCE AND COMPLEXITY OF RADIOSITY ALGORITHMS
Laszlo Szirmay-Kalos and Gabor Marton
Department of Process Control
Technical University of Budapest
Budapest, Müevetem rkp. 11,H-111
Hungary
e-mail szirmay@fsz.bme.hu
This paper evaluates and compares the convergence and
complexity characteristics of radiosity algorithms with
a special emphasis on randomized methods.
Keywords: Radiosity method, complexity evaluation,
randomized algorithms
VEGA : VIENNA ENVIRONMENT FOR GRAPHICS APPLICATIONS
Robert F. Tobler, Helwig Löffelmann,
Werner Purgathofer
Institute of Computer Graphics
Technical University of Vienna
A-1040 Karlsplatz 13/186/2
e-mail rft@cg.tuwien.ac.at, helvig@cg.tuwien.ac.at,
wp@cg.tuwien.ac.at
This paper presents a software development environment for
rendering applications. The main parts of this environment
are a set of rules concerning the coding style, a set of
tools to maintain source files and a number of libraries
providing graphics functionality. The environment has been
succesfully used in a number of internal projects, dealing
with rendering.
A ROBUST OBJECT MODELING SYSTEM USING A RANGE FINDER
Takashi Wada, Tatsuro Nakamura, Kaoru Suzuki
Kansai Research Lab. Toshiba
8-6-26 Motoyoma-Minami-machi, Higashi-Nada-ku, Kobe, 658 Japan
Multimedia Engineering Lab. Toshiba
209, Suhiro-chou, Ome, Tokyo, 198 Japan
e-mail wada@krl.toshiba.co.jp,
tatsuro@mmfive.pms.mmlab.toshiba.co.jp
suzuki@krl.toshiba.co.jp
This paper presents a robust object modeling system that
generates an object model from multiviewing range data. The
purpose of the system is to obtain an exact model, overcoming
a noise problem in range data. Our system computes object
existence in voxel space by integrating observations form
multi-viewpoints. The noise in range data is excluded by this
integration process. Then, a triangular mesh is efficiently
obtained by using adjacent relationships between voxels.
Finally, a fine object model is acquired by associating
brightness values in color image with the vertex on the mesh.
Experiments are performed for plural real objects (dolls and
a cup) and effectiveness of the system is shown.
FREE FORM SURFACE CONSTRUCTION USING GREGORY PATCHES
Shouqing Zhang, A.L.Thomas
e-mail: S.Zhang@central.sussex.ac.uk
This paper deals with the construction of a free form surface
by using both triangular and rectangular Gregory patches.
The input is a set of 3D points associated with normal values
at each point. All the control points needed for Gregory
patch can then be calculated automatically to achieve the G1
continuity between neighbouring patches within surface.
Keywords: Gregory patch, Triangular and Rectangular shape,
G1 continuity
EMPLOYING CONSTRAINTS TO FONTS
Borut Zalik, Fiaz Hussain and Nikola Guid
University of Maribor
Faculty of Technical Scienes
Department of Computer Science
Smetanova 17, SI-62000 Maribor
Slovenia
e-mail zalik@uni-mb.si, fiaz@dmu.ac.uk
This paper gives a new approach for describing the outlines
of characters. It uses geometric constraints to model
characteristics of fonts. Such an approach is known to have
applications in the area of rasterization, where so-called
hints are introduced to maintain character legibility at low
resolutions. In order to promote flexibility and performance,
the technique outlined uses the principle of localised
constraints. Its basic features are highlighted via its
application on the Bezier cubic curve.
Keywords : Bezier, constraint-based design,
feature-based design, constraint solving, font, hints,
rasterisation.
TEXTURE CLASSIFICATION BY NEURAL NET IN MEDICAL SONOGRAPHY
V. Cerny, L. Fekete, R. Zajac
Institute of Physics, Comenius University
Mlynska dolina, 842 15 Bratislava, Slovakia
Department of Urology, Medical Faculty Hospital
Hlboka 7, 811 05 Bratislava, Slovakia
e-mail cerny@fmph.uniba.sk
We have developed a simple neural net classifier to evaluate
textural informational content in the sonographic medical
images. The net is trained on a set of texture patterns from
sonographic images of testes. The samples in the set were
classified by the supervisor into two classes: "normal" and
"tumor". After training the performance was 85% correctly
classified images. We are in the stage of collecting data for
the independent test set of samples.
A NOTE TO THE STRUCTURE OF BRESENHAM SLICE ALGORITHM
Tomas Hruz, Ivo Povazan
Slovak Technical University
Faculty of Mechanical Engineering
Namestie Slobody 17
812 31 Bratislava, Slovakia
Institute of Control Theory and Robotics
Slovak Academy of Sciences
Dubravska cesta 9
842 37 Bratislava, Slovakia
e-mail hruz@cvt.stuba.sk, utrrpova@savba.savba.sk
This paper gives a complete analysis of the structure of
segments (spans) of points with a constant y-coordinate,
which are observed in the Bresenham Slice algorithm. In
particular, we show that this structure is related to the
greatest common divisor of the end-point coordinates.
SCIENTIFIC VISUALIZATION WITH MAPLE
Jiri Hrebicek
Waterloo MAPLE software GmbH, Heidelberg
Abstract is not available.
CATIA SOLUTIONS VERSION 4 - THE OVERVIEW OF THE CAD/CAM/CAE
SYSTEM
Ing. Miroslav Kral
IBM
Czech Republic
CATIA Solutions Version 4 builds on more than a decade of
proven marketplace success for CATIA, which currently has
more than 4 000 customers of all sizes worldwide in
industries ranging from general manufacturing to aerospace,
automotive and customer goods. CATIA is internationally
recognized as an industry leader because it has benefited so
many users and because of its comprehensive, integrated
approach to the entire product design, manufacture and
support process.
REDUCING THE NUMBER OF SHADOW RAYS IN BIDIRECTIONAL PATH
TRACING
Eric P. Lafortune, Yves D. Willems
Department of Computer Science
Katholieke Universität Leuven
Celestijnlaan 200A, 30001 Heverlee, Belgium
e-mail Eric.Lafortune@cs.kuleuven.ac.be
Bidirectional path tracing is a fairly new Monte Carlo
algorithm for physically based rendering. Introduced as
a generalisation of path tracing, the algorithm traces paths
for each pixel, not only from the eye point but also from the
light sources. It subsequently links the intersection points
on the respective paths by means of shadow rays. Each shadow
ray determines if a lighting contribution has to be added to
the estimate of the radiance of the pixel.
In this paper we present a technique which reduces
the number of shadow rays that are traced effectivelly. The
resulting slight increase in the variance of the stochastic
process can be undone by taking more samples. Practical tests
show that the approach yields a reduction of the variance for
the same amount of work.
SIMULATING FEATURE-BASED MODELLING IN PROGRAMMING-BY-EAMPLE
PARAMETRIC CAD
Evgueni N. Loukipoudis and Jan A.A. Melkebeek
Department of Electrical Power Engineering
University of Gent
Sint-Pietersnieuwstraat 41, B-9000 Gent, Belgium
As an alternative to the development of a full feature-based
CAD system, we suggest a fairly simple extension to a system
that possesses parametric capabilities so that feature-based
modelling interface is simulated. We use
programming-by-example in defining features by parametric
programs following a purely procedural approach. The
parametric programs constitute the feature model which is
built up in a bottom-up manner. The structuring of the object
in features allows modifications to the parametric
description in a graphical manner. Some problems related to
the use of feature in an engineering system for the purpose
of simulation and analysis as well as the handling of duality
and comlementarity in a feature model are discussed. We have
restricted our approach to 2D models and have implemented
Electric Machinery specific features into 2D CAD system.
STEREOGRAPHIC VISUALIZATION OF TURBULENT PIPE FLOWS
USING ANALYPHS WITH TWOFOLD CENTRAL PROJECTION
Wolfgang Messner, Walter Huber
Technische Universität München
Institut für Informatik
Lehrstuhl für Ingenieuranwendungen in der Informatik
D-80290 München, Germany
e-mail messner,huberw@informatik.tu-muenchen.de
The size of velocity-vector fields obtained from numerical
solutions of the Navier-Stokes equations for
three-dimensional, time varying and turbulent flows is
extremely large. Stereographic systems can intuitively depict
the small depth movements and relations between fluid
particles that standard perspective projections fail to. As
expensive high-end-stereographics systems aim at one user one
computer and are therefore not suitable for demonstration
purposes in lectures, the anaglyphic method is applied for
visualizing turbulence in a stereographic movie to a large
number of people. A solution to overcome the effect of
ghosting, which has been a major drawback in the use of
anaglyphs, is introduced. A twofold central projection was
found to be superior to standard on-axis projections in
graphics harware allowing an easy representation of objects
in front of and behind the projection plane and thus
enhancing the stereoscopis effect. The visualization system
deals with the small fluctuations of the velocity about its
mean values (i.e. the so called rms values) to depict real
turbulence in a pipe flow at reynolds number Re approx.7000.
SOUND MAPPINGS FOR SURFACE VISUALIZATION
Rosane Minghim and A.R.Forrest
University of East Anglia
School of Information Systems
Norwich NR4 7TJ
UK
e-mail rm@sys.uea.ac.uk, forrest@sys.uea.ac.uk
This paper is concerned with the development of a system to
support Scientific Visualization by utilising the sound
channel. The mappings presented here are intended to support
understanding and interaction with surface data. This is done
by using sound signals associated with methods of analysis of
surfaces to help the interpretation of surface shape, data,
and classification. Several examples of sound mappings are
presented and the implications for data interaction are
discussed.
A PARALLEL RADIOSITY SYSTEM FOR LARGE DATA SETS
David Stuttart, Adam Worrall,
Derek Paddon and Claire Willis
Department of Computer Science
University of Bristol
Bristol, BS8 1TR, UK
e-mail derek@compsci.bristol.ac.uk
The radiosity method gives realistic results for syhtnesising
images based on diffuse light interaction; however, the
method is also very computationally expensive. Here we
present a system for parallelising a progressive refinement
radiosity method using a ray casting approach. The system
decomposes the environment into two distinct entities, the
model geometry and the radiosity sample points. These are
then distributed amongst the processors and message passing
communication protocols and caching methods are introduced
to enable the system to cope with very large models while
maintaining a high processing rate.
COMPUTER ANIMATION AND HUMAN ANIMATORS
Philip J. Willis
Computing Group, School of Mathematical Sciences
University of Bath
Claverton Down. Bath BA2 7AY, UK
e-mail P.J.Willis@bath.ac.uk
There is often a gap between what technology can deliver and
what users want. Sometimes this is because of fundamental
technological constraints but often it is because
technologists do not address the realities of user needs and
expectations before attempting to solve the problem.
The talk will describe our approach to computer
animation and some of the pitfalls of trying to address
a community which is visually more literate than typical
computer graphic people, while being far less computer
oriented.
Keywords : computer animation, animation
LOAD BALANCING FOR PARALLEL RAYTRACER ON VIRTUAL WALLS
Jiri Zara, Ales Holecek, Jan Prikryl,
Jan Burianek, Knut Menzel
e-mail zara@cs.felk.cvut.cz, holecek@sgi.felk.cvut.cz,
prikryl@sgi.felk.cvut.cz, xburiane@sgi.felk.cvut.cz,
knut@uni-paderborn.de
Dynamic load balancing of parallel ray-tracing algorithm
based on spacial subdivision is discussed. We attempt to find
the load balancing method with the fastest respond on the
load extreams in the system. An optimal architecture of the
computational system based on three level process hierarchy
is proposed. The scene partitioning is based on Virtual Walls.
Keywords : computer graphics, rendering, parallel algorithm,
ray-tracing, load-balancing
GEOMETRIC MODELLING IN A THREE-DIMENSIONAL ENVIRONMENT
G.J. Clapworthy, R.A. Noble
Department of Computer & Information Sciences
De Montfort University
Hammerwood Gate
Kents Hill
Milton Keynes, MK7 6HP
e-mail gclapwor@dmu.ac.uk
Computer animators have long had difficulties in defining and
controlling the shape of deformable objects during motion. In
the context of human figure animation, a new form of surface
description has been developed. Murugaiyan \& Clapworthy [1],
which allows the surface to be manipulated by adjustment of
a single parameter. The form of the surface deformations
produced by the operations is under the control of the user.
The mathematical structures used are extensions of NURBS,
but have a greater flexibility at the cost of
marginally-increased overheads.
The development of this tool enables the surface
modelling of a deformable object to be speeded up
considerably, and the paper describes a geometric modeller
currently under construction which will use this facility to
produce the desired object by 'virtual sculpting', a process
analogous to the production of real objects from clay. In
this, the user is able to pull and push the surface shape
to produce either rounded or shaped surface indentations or
protrusions by direct interaction with the surface.
The object is viewed stereoscopically and at present
shutter glasses are used. These have the attendant problem of
ghosting, but this can be removed by a subtract-from-background
algorithm, Noble [2]. Ongoing work at De Monfort university
[3,4] will eventually allow enhancement using autostereoscopic
displays and eye tracking.
The object is oriented in three dimensions using
a spaceball and the surface operations are controlled using
a mouse. The reduction in the number of paremeters employed
in the surface description enables the operations on the
surface to be performed by the use of the mouse buttons.
Thus, the shape of the object is defined by simple 'point and
click' operations providing an extremely rapid, interactive
method of surface construction.
It is anticipated that this modelling system could be
used in a number of areas of work, including Virtual Reality.
While the tool is still at the developmental stage,
the paper lays out the complete conceptual basis for
its construction and implementation.
USING OF DISCRIMINATORY ANALYSIS TO PATTERN RECOGNITION
OF TACTILE PATTERN
Jaromir Volf
Czech Technical University
Faculty of Mechanical Engineering
Technicka 4, 166 07 Prague 6
Czech Republic
Tel.:+422 24 35 27 37, fax +422 24 31 02 92
e-mail volf@fsid.cvut.cz
This papre described a new method of tactile pattern
recognition. The method can be used a numeric regulator, too.
This method is based on the discriminatory analysis. The
computation is going through all system of pattern classes.
This corresponds to classical computing process, which is
used in the discriminatory analysis. The Ivanovic deviation
is used as discriminatory function. The m dimensional vector
is impute and the method can classify into n groups of
patterns. Pattern recognition can work at a real time.
Keywords : discriminatory analysis, tactile, pattern, image,
pattern recognition
COMPARISON OF SOME RAY GENERATORS FOR RAY TRACING
VOLUMETRIC DATA
Milos Sramek
Institute of Measurement Science
Slovak Academy of Sciences
Dubravska cesta 9
842 19 Bratislava, Slovak Republic
Ray tracing is a popular technique for rendering not only
analytical objects, but also volumetric data, either
synthetized or measured. Different techniques for the ray
definition by traversal of the voxel space were designed. The
first part of the paper is an overview of ray tracing or ray
casting algorithms for the volume data. Stress is laid upon
exploiting various kinds of speed up techniques. In the
second part, we compare some of these approaches in
a computer experiment. Further we show that an appropriate
choice of background traversal algorithm can significantly
shorten computation time of the exact ray-surfrace
intersection point.
GRAPHICAL REPRESENTATION OF RULES
IN AN OBJECT-ORIENTED ENVIRONMENT
Kenneth Messa, Bogdan Czejdo, Erick Villalobos
Department of Mathematics and Computer Science
Loyola University
New Orleans, LA
U.S.A.
In this paper a graphical representation of rules is
proposed. The graphical rules are formulated based on
Extended Entity-Relationship (EER) diagrams. Such diagrams
are compiled into an object-oriented language code that is
included as a component of the developed software system.
Other components can be directly coded in an object-oriented
language or generated using other graphical tools. We
identify and discuss two types of graphical rules : class
graphical rules and instance graphical rules. The syntax and
semantics of both types of graphical rules are discussed. The
graphical rules can contain object-oriented code in addition
to graphical diagrams. The methods of integration of diagram
and object-oriented code are described.
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