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@article{Rougeron:1998:CFI,
author = {G. Rougeron and B. P{\'{e}}roche},
title = {Color Fidelity in Computer Graphics: A Survey},
volume = {17},
number = {1},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {3-16},
note = {{ISSN} 1067-7055},
keywords = {Spectral Rendering, Colorimetry, Vision Model,
Color Monitor Model},
annote = {The purpose of this paper is to make a state of the
art for color fidelity in computer graphics. Color fidelity
includes three steps. The first one is the spectral rendering
phase which attributes a spectrum to each pixel of a picture.
During the second step, a spectral data is transformed into a
set of tristimulus values in the {XYZ} color space. The purpose of
the third step, called Color Reproduction Function, is to
determine the {RGB} values displayable on the screen, in such a
way that subjective fidelity is reached. We especially detail
the two last steps of the color fidelity process; we also point
out the work still remaining to be done in this field and we
propose some research ways. },
}
@article{Fischer:1998:AAF,
author = {M. Fischer},
title = {An Algorithm for Dynamic Color Management},
volume = {17},
number = {1},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {17-28},
note = {{ISSN} 1067-7055},
keywords = {color management, color reduction, dynamic color
allocation, platform independence, high quality graphics},
annote = {Though the problem of color quantization in static
images is not completely solved, there are a few algorithms that
produce good results. Color quantization with dynamic color
requests is an unsolved problem. In this paper we present an
algorithm that manages dynamic color allocations without advance
knowledge of the sequence of color requests. It uses a dynamic
color table that can be used simultaneously in multiple windows
from one or more applications. Advance knowledge about color
requirements will improve the results of the algorithm. },
}
@article{Genetti:1998:ASI,
author = {J. Genetti and D. Gordon and G. Williams},
title = {Adaptive Supersampling in Object Space Using
Pyramidal Rays},
volume = {17},
number = {1},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {29-54},
note = {{ISSN} 1067-7055},
keywords = {Computer graphics, picture/image generation,
three-dimensional graphics and realism, anti-aliasing,
distributed light sources, fuzzy reflections, penumbra,
object-space, ray tracing, stochastic sampling, adaptive,
supersampling},
annote = {We introduce a new approach to three important
problems in ray tracing: antialiasing, distributed light
sources, and fuzzy reflections of lights and other surfaces. For
antialiasing, our approach combines the quality of supersampling
with the advantages of adaptive supersampling. In adaptive
supersampling, the decision to partition a ray is taken in
image-space, which means that small or thin objects may be
missed entirely. This is particularly problematic in animation,
where the intensity of such objects may appear to vary. Our
approach is based on considering pyramidal rays (pyrays) formed
by the viewpoint and the pixel. We test the proximity of a pyray
to the boundary of an object, and if it is close (or marginal),
the pyray splits into 4 sub-pyrays; this continues recursively
with each marginal sub-pyray until the estimated change in pixel
intensity is sufficiently small. The same idea also solves the
problem of soft shadows from distributed light sources, which
can be calculated to any required precision. Our approach also
enables a method of defocusing reflected pyrays, thereby
producing realistic fuzzy reflections of light sources and other
objects. An interesting byproduct of our method is a substantial
speedup over regular supersampling even when all pixels are
supersampled. Our algorithm was implemented on polygonal and
circular objects, and produced images comparable in quality to
stochastic sampling, but with greatly reduced run times. },
}
@article{James:1998:TPF,
author = {A. James and A. Ray},
title = {The Priority Face Determination Tree for Hidden
Surface Removal},
volume = {17},
number = {1},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {55-72},
note = {{ISSN} 1067-7055},
annote = {Many virtual environments are built from a set of
polygons that form the basis of objects in the scene. Using
priority-list algorithms, the sequence in which these polygons
are drawn is dependent upon the location of an observer; the
polygons must be ordered correctly before a realistic image can
be displayed. It is necessary for a scene to be drawn correctly
in real time from all locations before the observer can move
interactively around the scene with complete freedom. The
binary-space partitioning (BSP) tree developed by Fuchs, Kedem
and Naylor in 1980 stores the view independent priority, of a
set of polygons which can be used to obtain the correct order
for any given viewpoint. However, the number of polygons grows
significantly due to the {BSP} splitting stage, increasing the
number of nodes in the tree. This affects linearly the number of
tests necessary to traverse the tree to obtain the priority of
the set of polygons. The algorithm presented here is built using
its associated {BSP} tree, but attempts to reduce the number of
tests to log4/3 n, at the cost of a tree of size of
O(N1.5log4/3n-1, where n is the initial number of polygons in
the scene, and N the resulting number qfter {BSP} splitting. To
achieve the increase in run-time efficiency, a height plane is
used to restrict the view point of the observer to a fixed
height, but the key to the efficiency of the algorithm is in the
use of polygonal dependencies. In the scene, if we know our
location relative to the front or back of a polygon, then our
position relative to one-quarter of the remaining polygons, in
the expected worst-case, can be determined. },
}
@article{Lintermann:1998:AMM,
author = {B. Lintermann and O. Deussen},
title = {A Modelling Method and User Interface for Creating
Plants},
volume = {17},
number = {1},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {73-82},
note = {{ISSN} 1067-7055},
annote = {We present a modelling method and graphical user
interface for the creation of natural branching structures such
as plants. Structural and geometric information is encapsulated
in objects that are combined to form a description of the model.
The model is represented graphically as a structure graph and
can be edited interactively. Global and partial constraint
techniques are integrated on the basis of tropisms, free-form
deformations and pruning operations to allow the modelling of
specific shapes. We show examples to illustrate the design
process and evaluate the user interface. },
}
@article{McCormack:1998:CAR,
author = {Jon McCormack and Andrei Sherstyuk},
title = {Creating and Rendering Convolution Surfaces},
volume = {17},
number = {2},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers },
pages = {113-120},
note = {{ISSN} 1067-7055},
annote = {Implicit surfaces obtained by convolution of
multi-dimensional primitives with some potential function, are a
generalisation of popular implicit surface models: blobs,
metaballs and soft objects. These models differ in their choice
of potential function but agree upon the use of underlying
modelling primitives, namely, points. In this paper a method is
described for modelling and rendering implicit surfaces built
upon an expanded set of skeletal primitives: points, line
segments, polygons, arcs and planes. An analytical solution to
the convolution is described. This solution offers a more
accurate and robust representation of the resultant implicit
surface than previous methods. An algorithm for ray-tracing the
surfaces formed through convolution of any combination of these
primitives is also outlined. },
}
@article{Vemuri:1998:FCD,
author = {B. C. Vemuri and Y. Cao and L. Chen},
title = {Fast Collision Detection Algorithms with
Applications to Particle Flow},
volume = {17},
number = {2},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {121-134},
note = {{ISSN} 1067-7055},
annote = {In this paper, we present efficient algorithms for
collision detection of arbitrarily shaped rigid moving objects
in a variety of interactive as well as non-interactive
environments. The algorithms primarily consist of two stages.
The first stage involves finding candidate objects for possible
collisions. The second stage involves detecting exact (within a
prespecified tolerance) collision between these candidates. The
primary data structure used in the algorithms is an octree. In
the first stage, we build an octree for the enclosure containing
the objects, which is used to detect possible collisions.
Assuming spatial/temporal coherence i.e., that the particles
move slowly or that the time sampling is fast enough, the
average time complexity of this stage can be shown to be O(n)
(excluding the time complexity for a one time octree
construction), where n is the number of particles. In the second
stage, we build a surface-octree for each object. If the objects
are convex and assuming coherence, the expected time complexity
to detect precise (within a prespecified tolerance) collision
for each pair is a constant (excluding the time complexity for a
one time surface-octree construction). Therefore, the overall
expected time complexity for convex object collision detection
is linear with respect to n. For the concave objects, complexity
analysis is nontrivial to perform and instead we provide a very
practical (almost linear time) algorithm. We apply our
algorithms to particle flow simulations by simulating flow
density conditions often arising in granular flows. },
}
@article{Turner:1998:ICA,
author = {Russell Turner and Enrico Gobbetti},
title = {Interactive Construction and Animation of Layered
Elastically Deformable Characters},
volume = {17},
number = {2},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {135-152},
note = {{ISSN} 1067-7055},
annote = {An interactive system is described for creating and
animating deformable {3D} characters. By using a hybrid layered
model of kinematic and physics-based components together with an
immersive {3D} direct manipulation interface, it is possible to
quickly construct characters that deform naturally when animated
and whose behavior can be controlled interactively using
intuitive parameters. In this layered construction technique,
called the elastic surface layer model, a simulated elastically
deformable skin surface is wrapped around a kinematic
articulated figure. Unlike previous layered models, the skin is
free to slide along the underlying surface layers constrained by
geometric constraints which push the surface out and spring
forces which pull the surface in to the underlying layers. By
tuning the parameters of the physics-based model, a variety of
surface shapes and behaviors can be obtained such as more
realistic-looking skin deformation at the joints, skin sliding
over muscles, and dynamic effects such as squash-and-stretch and
follow-through. Since the elastic model derives all of its input
forces from the underlying articulated figure, the animator may
specify all of the physical properties of the character once,
during the initial character design process, after which a
complete animation sequence can be created using a traditional
skeleton animation technique. Character construction and
animation are done using a {3D} user interface based on two-handed
manipulation registered with head-tracked stereo viewing. In our
configuration, a six degree-of-freedom head-tracker and
CrystalEyes shutter glasses are used to display stereo images on
a workstation monitor that dynamically follow the user head
motion. {3D} virtual objects can be made to appear at a fixed
location in physical space which the user may view from
different angles by moving his head. To construct {3D} animated
characters, the user interacts with the simulated environment
using both hands simultaneously: the left hand, controlling a
Spaceball, is used for {3D} navigation and object movement, while
the right hand, holding a {3D} mouse, is used to manipulate
through a virtual tool metaphor the objects appearing in front
of the screen. Hand-eye coordination is made possible by
registering virtual space to physical space, allowing a variety
of complex {3D} tasks necessary for constructing {3D} animated
characters to be performed more easily and more rapidly than is
possible using traditional interactive techniques. },
}
@article{Herman:1998:TVA,
author = {Ivan Herman and Maylis Delest and Guy Melancon},
title = {Tree Visualisation and Navigation Clues for
Information Visualisation},
volume = {17},
number = {2},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {153-165},
note = {{ISSN} 1067-7055},
annote = {Information visualisation often requires good
navigation aids on large trees, which represent the underlying
abstract information. Using trees for information visualisation
requires novel user interface techniques, visual clues, and
navigational aids. This paper describes a visual clue: using the
so-called Strahler numbers, a map is provided that indicates
which parts of the tree are interesting. A second idea is that
of "folding" away subtrees that are too "different" in some
sense, thereby reducing the visual complexity of the tree.
Examples are given demonstrating these techniques, and what the
further challenges in this area are. },
}
@article{Cignoni:1998:ME,
author = {Paolo Cignoni and C. Rocchini and Roberto
Scopigno},
title = {Metro: Measuring Error on Simplified Surfaces},
volume = {17},
number = {2},
journal = {Computer Graphics Forum},
year = {1998},
publisher = {Blackwell Publishers},
pages = {167-174},
note = {{ISSN} 1067-7055},
annote = {This paper presents a new tool, Metro, designed to
compensate for a deficiency in many simplification methods
proposed in literature. Metro allows one to compare the
difference between a pair of surfaces (e.g. a triangulated mesh
and its simplified representation) by adopting a surface
sampling approach. It has been designed as a highly general
tool, and it does no assumption on the particular approach used
to build the simplified representation. It returns both
numerical results (meshes areas and volumes, maximum and mean
error, etc.) and visual results, by coloring the input surface
according to the approximation error. },
}
@article{Durikovic:1998:AOB,
author = {Roman Durikovic and Kazufumi Kaneda and Hideo
Yamashita},
title = {Animation of Biological Organ Growth Based on
L-systems},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {1-14},
note = {{ISSN} 1067-7055},
annote = {In contrast with the growth of plants and trees,
human organs can undergo significant changes in shape through a
variety of global transformations during the growth period, such
as bending or twisting. In our approach, the topology of a human
organ is represented by a skeleton in the form of a tree or
cycled graph. The length of skeleton growth can be simulated by
an algebraic L-system that also produces discrete events. The
paper shows how to include global transformations into the
formalism of L-systems to obtain a continuous process. The shape
of the organ is approximated by a number of ellipsoidal clusters
centred at points on the skeleton. The proposed growth model of
the organ continually responds to the positional changes of
surrounding organs, thereby changing the organ shape locally. In
our study, the stomach of a human embryo is used for the
demonstration of organ development, and the methodology employed
is also applicable to the animation of animal organs and their
development. },
}
@article{Lee:1998:FFM,
author = {Tong-Yee Lee and Young-Ching Lin and Leeween Lin
and Y. N. Sun},
title = {Fast Feature-Based Metamorphosis and Operator
Design},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {15-22},
note = {{ISSN} 1067-7055},
annote = {Metamorphosis is a powerful visual technique, for
producing interesting transition between two images or volume
data. Image or volume metamorphosis using simple features
provides flexible and easy control of visual effect. The
feature-based image warping proposed by Beier and Neely is a
brute-force approach. In this paper, first, we propose
optimization methods to reduce their warping time without
noticeable loss of image quality. Second, we extend our methods
to {3D} volume data and propose several interesting warping
operators allowing global and local metamorphosis of volume
data. },
}
@article{Bao:1998:I3M,
author = {Hujun Bao and Qunsheng Peng},
title = {Interactive {3D} Morphing},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {23-30},
note = {{ISSN} 1067-7055},
annote = {A new {3D} morphing algorithm for polyhedral objects
with the same genus is presented in the paper. Our main
contribution is an efficient and general algorithm for setting
up the vertex correspondence between the polyhedra. The proposed
algorithm first interactively partitions the two original
polyhedra into the same number of polygonal patches, the patch
correspondence is also established during partitioning. Each
pair of corresponding patches is then parametrized and resampled
bv using the harmonic maps. A feature polyhedron is finally
constructed for each original polyhedron, and the vertex
correspondence between each original polyhedron and its feature
polyhedron is automatically established following a cluster
scheme. The shape transition between the original polyhedral
models is accomplished by composing three successive
transformations using their feature polyhedra as the bridges.
Experimental results demonstrate that our algorithm is verv
robust, and can deal with very general cases (non-zero genus
polyhedral cases). },
}
@article{Grimm:1998:AFF,
author = {Cindy Grimm and Matthew Ayers},
title = {A Framework for Synchronized Editing of Multiple
Curve Representations},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {31-40},
note = {{ISSN} 1067-7055},
keywords = {direct manipulation, interface issues, curve
manipulation},
annote = {Editing curves and surfaces is difficult in part
because their mathematical representations rarely correspond to
most people's idea of a curve or surface. The implementation
(and hence, behavior) of most manipulation tools is intertwined
with a particular curve or surface representation; this can make
reimplementing the tool with a different representation
problematic. A system using a single representation must
therefore either limit the types of tools available or convert
existing tools to work on the system's representation. \\ In
this paper we present a framework for editing curves or surfaces
which supports multiple representations and ensures that they
stay synchronized. As a proof of concept, we have created a
curve editor which contains several tools each of which
manipulate one of three different curve representations:
polylines, {NURBS}, and multi-resolution B-splines. },
}
@article{Poupyrev:1998:EOM,
author = {I. Poupyrev and S. Weghorst and M. Billinghurst and
T. Ichikawa},
title = {Egocentric Object Manipulation in Virtual
Environments: Evaluation of Interaction Techniques},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {41-52},
note = {{ISSN} 1067-7055},
annote = {The acceptance of virtual environment (VE)
technology requires scrupulous optimization of the most basic
interactions in order to maximize user performance and provide
efficient and enjoyable virtual interfaces. Motivated by
insufficient understanding of the human factors design
implications of interaction techniques and tools for virtual
interfaces, this paper presents results of a formal study that
compared two basic interaction metaphors for egocentric direct
manipulation in VEs, virtual hand and virtual pointer, in object
selection and positioning experiments. The goals of the studv
were to explore immersive direct manipulation interfaces,
compare performance characteristics of interaction techniques
based on the metaphors of interest, understand their relative
strengths and weaknesses, and derive design guidelines for
practical development of {VE} applications. },
}
@article{Lu:1998:ACS,
author = {Tain-chi Lu and Chuanwen Chiang and Ming-tang Lin
and Chungnan Lee},
title = {A Collaborative Scene Editor for {VRML} Worlds},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {53-62},
note = {{ISSN} 1067-7055},
keywords = {collaboration, {VRML}, Java, {CSCW}, multi-user
environment},
annote = {In this paper, we analyze the requirements for a
Web-based collaborative infrastructure within a virtual world.
Additionally, we combine several tools and methodologies to
propose a flexible and fluid collaborative environment using
Java language to create a {VRML} scene graph. The proposed
prototype aims at four aspects: a shared workspace of scene
editor, an active entity composition algorithm in Java,
collaborative control in the multi-user environment, and access
control mechanism toward the shared data. },
}
@article{Paquette:1998:ALH,
author = {Eric Paquette and Pierre Poulin and George
Drettakis},
title = {A Light Hierarchy for Fast Rendering of Scenes with
Many Lights},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {63-74},
note = {{ISSN} 1067-7055},
keywords = {image synthesis, rendering, ray-tracing,
hierarchy, illumination, reflection, Phong, bounds, clustering,
octree},
annote = {We introduce a new data structure in the form of a
light hierarchy for efficiently ray-tracing scenes with many
light sources. An octree is constructed with the point light
sources in a scene. Each node represents all the light sources
it contains by means of a virtual light source. We determine
bounds on the error committed with this approximation to shade a
point, both for the cases of diffuse and specular reflections.
These bounds are then used to guide a hierarchical shading
algorithm. If the current level of the light hierarchy provides
shading of sufficient quality, the approximation is used, thus
avoiding the cost of shading for all the light sources contained
below this level. Otherwise the descent into the light hierarchy
continues. \\ Our approach has been implemented for scenes
without occlusion. The results show important acceleration
compared to standard ray-tracing (up to 90 times faster) and an
important improvement compared to Ward's adaptive shadow
testing. },
}
@article{Park:1998:OFR,
author = {Tae-Joon Park and Seungyong Lee and Sung Yong
Shin},
title = {Optical Flow Rendering},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {75-86},
note = {{ISSN} 1067-7055},
keywords = {image-based rendering, optical flow, stereo
matching, depth information, warp function, statistical
analysis, image composition},
annote = {This paper proposes a new approach to image-based
rendering that generates an image viewed from an arbitrary
camera position and orientation by rendering optical flows
extracted from reference images. To derive valid optical flows,
we develop an analysis technique that improves the quality of
stereo matching. Without using any special equipments such as
range cameras, this technique constructs reliable optical flows
from a sequence of matching results between reference images. We
also derive validity conditions of optical flows and show that
the obtained flows satisfy those conditions. Since environment
geometry is inferred from the optical flows, we are able to
generate more accurate images with this additional geometric
information. Our approach makes it possible to combine an image
rendered with optical flows with an image generated by a
conventional rendering technique through a simple Z-buffer
algorithm. },
}
@article{Dischler:1998:AST,
author = {J. M. Dischler and D. Ghazanfarpour and R.
Freydier},
title = {Anisotropic Solid Texture Synthesis Using Orthogonal
2D Views},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {87-96},
note = {{ISSN} 1067-7055},
keywords = {realistic texturing, anisotropic solid texture
synthesis, spatial and spectral analysis, filtering, histogram},
annote = {Analytical approaches, based on digitised {2D}
texture models, for an automatic solid (3D) texture synthesis
have been recently introduced to Computer Graphics. However,
these approaches cannot provide satisfactory solutions in the
usual case of natural anisotropic textures (wood grain for
example). Indeed, solid texture synthesis requires particular
care, and sometimes external knowledge to "guess" the internal
structure of solid textures because only {2D} texture models are
used for analysis. By making some basic assumptions about the
internal structure of solid textures, we propose a very
efficient method based on a hybrid analysis (spectral and
histogram) for an automatic synthesis of solid textures. This
new method allows us to obtain high precision solid textures
(closely resembling initial models) in a large number of cases,
including the difficult case of anisotropic textures. },
}
@article{Sloan:1998:IDT,
author = {Peter-Pike J. Sloan and David M. Weinstein and J.
Dean Brederson},
title = {Importance Driven Texture Coordinate Optimization},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {97-104},
note = {{ISSN} 1067-7055},
keywords = {texture mapping, texture map distortion,
interaction},
annote = {Traditionally, texture coordinates have been
generated based solely on the model's geometry, often even
before a model's textures have been created. With the arrival of
new technologies, such as {3D} paint programs, weaknesses of a
static optimization pre-process are becoming apparent. These
weaknesses arise from constructing a parameterization based
solely on the model's geometry, ignoring the fact that detail is
not uniformly spaced throughout the texture space. In fact,
certain regions of the texture are more important than other
regions. In this paper we introduce the notion of the
"importance map" and describe how importance values are derived
from both intrinsic properties of the texture and user-guided
highlights. Furthermore, we describe how importance maps are
used to drive the texture coordinate optimization. Finally, we
show how this optimization process can be integrated into a {3D}
painting environment, enabling periodic optimization at any
stage of texture design. },
}
@article{Buchanan:1998:SWU,
author = {John W. Buchanan},
title = {Simulating Wood Using a Voxel Approach},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {105-112},
note = {{ISSN} 1067-7055},
keywords = {voxels, solid texture, soft wood, knots},
annote = {In this paper we present a technique for generating
three-dimensional wood textures using a regular texture array.
Currently three-dimensional wood textures are generated using
procedural textures. Procedural textures are flexible and
require little memory, however the modeling of local artifacts
such as knots is difficult using the procedural approach. By
representing the wood as a texture array and growing the wood in
this array we can easily simulate local phenomena such as knots.
Our growth model is an approximation to the biological model and
assumes that there are several similar wood cells per array
element. This means that we can model artifacts that are defined
bv groups of similar cells. In particular our model is well
suited for the modeling of soft-woods. },
}
@article{Cai:1998:PIE,
author = {Wenli Cai and Georgios Sakas and Roberto Grosso and
Thomas Ertl},
title = {Progressive Iso-Surface Extraction from Hierarchical
3D Meshes},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {125-136},
note = {{ISSN} 1067-7055},
keywords = {volume rendering, {MIP}, splatting, shear warp},
annote = {A multiresolution data decomposition offers a
fundamental framework supporting compression, progressive
transmission, and level-of-detail (LOD) control for large two or
three dimensional data sets discretized on complex meshes. In
this paper we extend a previously presented algorithm for {3D}
mesh reduction for volume data based on multilevel finite
element approximations in two ways. First, we present efficient
data structures which allow to incrementally construct
approximations of the volume data at lower or higher resolutions
at interactive rates. An abstract description of the mesh
hierarchy in terms of a coarse base mesh and a set of integer
records offers a high compression potential which is essential
for an efficient storage and a progressive network transmission.
Based on this mesh hierarchy we then develop a new progressive
iso-surface extraction algorithm. For a given iso-value, the
corresponding iso-surface can be computed at different levels of
resolution. Changing to a higher or coarser resolution will
update the surface only in those regions where the volume data
is being refined or coarsened. Our approach allows to
interactively visualize very large scalar fields like medical
data sets, whereas the conventional algorithms would have
required at least an order of magnitude more resources. },
}
@article{Poston:1998:MIE,
author = {Tim Poston and Tien-Tsin Wong and Pheng-Ann Heng},
title = {Multiresolution Isosurface Extraction with Adaptive
Skeleton Climbing},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {137-148},
note = {{ISSN} 1067-7055},
annote = {An isosurface extraction algorithm which can
directly generate multiresolution isosurfaces from volume data
is introduced. It generates low resolution isosurfaces, with 4
to 25 times fewer triangles than that generated by marching
cubes algorithm, in comparable running times. By climbing from
vertices (0-skeleton) to edges (1-skeleton) to faces
(2-skeleton), the algorithm constructs boxes which adapt to the
geometry of the true isosurface. Unlike previous adaptive
marching cubes algorithms, the algorithm does not suffer from
the gap-filling problem. Although the triangles in the meshes
may not be optimally reduced, it is much faster than
postprocessing triangle reduction algorithms. Hence the coarse
meshes it produces can be used as the initial starts for the
mesh optimization, if mesh optimality is the main concern. },
}
@article{Zaninetti:1998:AVA,
author = {Jacques Zaninetti and Xavier Serpaggi and Bernard
P{\'{e}}roche},
title = {A Vector Approach for Global Illumination in Ray
Tracing},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {149-158},
note = {{ISSN} 1067-7055},
annote = {This paper presents a method taking global
illumination into account in a ray tracing environment. A vector
approach is introduced, which allows to deal with all the types
of light paths and the directional properties of materials.
Three types of vectors are defined: "Direct Light Vectors"
associated to light sources, "Indirect Light Vectors" which
correspond to light having been diffusely reflected at least
once and "Caustic Light Vectors" which are associated to light
rays emittedby sources and reflected and/or transmitted by
specular surfaces. These vectors are estimated at a small number
ofpoints in the scene. A weighted interpolation between known
values allows to reconstruct these vectors for the other points,
with the help of a gradient computation for the indirect
component. This approach also allows to take uniform area light
sources (spherical, rectangular and circular) into account for
all the types of vectors. Computed images are thus more accurate
and no discretizing of the geometry of the scene is needed. },
}
@article{Martin:1998:ATH,
author = {I. Martin and X. Pueyo and D. Tost},
title = {A Two-Pass Hardware-Based Method Hierarchical
Radiosity},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {159-164},
note = {{ISSN} 1067-7055},
annote = {Finite elements methods for radiosity are aimed at
computing global illumination solutions efficiently. However
these methods are not suitable for obtaining high quality imges
due to the lack of error control. Two-pass methods allow to
achieve that level of quality computing illumination at each
pixel and thus introducing a high computing overhead. We present
a two-pass method for radiosity that allows to produce high
quality images avoiding most of the per-pixel computations. The
method computes a coarse hierarchical radiosity solution and
then performs a second pass using current graphics hardware
accelerators to generate illumination as high definition
textures. },
}
@article{Stamminger:1998:GRO,
author = {M. Stamminger and H. Schirmacher and P. Slusallek
and Hans-Peter Seidel},
title = {Getting Rid of Links in Hierarchical Radiosity},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {165-174},
note = {{ISSN} 1067-7055},
annote = {Hierarchical radiosity with clustering has
positioned itself as one of the most efficient algorithms for
computing global illumination in non-trivial environments.
However using hierarchical radiosity for complex scenes is still
problematic due to the necessity of storing a large number of
transport coefficients between surfaces in the form of links. In
this paper, we eliminate the need for storage of links through
the use of a modified shooting method for solving the radiosity
equation. By distributing only unshot radiosity in each step of
the iteration, the number of links decreases exponentially.
Recomputing these links instead of storing them increases
computation time, but reduces memory consumption dramatically.
Caching may be used to reduce the time overhead. We analyze the
error behavior of the new algorithm in comparison with the
normal gathering approach for hierarchical radiosity. In
particular, we consider the relation between the global error of
a hierarchical radiosity solution and the local error threshold
for each link. },
}
@article{Jardillier:1998:SCF,
author = {Frank Jardillier and Eric Langu{\'{e}}nou},
title = {Screen-Space Constraints for Camera Movements: the
Virtual Cameraman},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {175-186},
note = {{ISSN} 1067-7055},
annote = {This article presents a virtual cameraman which
allows us to obtain the whole set of camera movements satisfying
user defined constraints specified in the image space and/or
constraints on the objects of the scene. This research follows
the "Declarative Modelling" approach, which focuses on a 3-phase
modeller concept: description; generation; result exploration.
\\ Our tool is based on a solver using interval arithmetic. The
time dimension is treated as another variable, thus constraints
can be specified for the total duration of the animation or
could last only for a given amount of time. There is no
keyframing and no interpolation, thereby, for the solutions
obtained, the satisfaction of the specified constraints are
guaranteed. Several wavs to include time dimension efficiently
are discussed. \\ We claim that the method is simple enough to
be implemented easily without the need of any external solver.
},
}
@article{Wang:1998:AWO,
author = {Yigang Wang and Hujun Bao and Qunsheng Peng},
title = {Accelerated Walkthroughs of Virtual Environments
Based on Visibility Preprocessing and Simplification},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {187-194},
note = {{ISSN} 1067-7055},
annote = {This paper proposes a new preprocessing method for
interactive rendering of complex polygonal virtual environments.
The approach divides the space that observer can reach into many
rectangular viewpoint regions. For each region, an outer
rectangular volume (ORV) is established to surround it. By
adaptively partitioning the boundary of the {ORV} together with
the viewpoint region, all the rays that originate from the
viewpoint region are divided into the beams whose potentially
visible polygon number is less than a preset threshold. If a
resultant beam is the smallest and intersects many potentially
visible polygons, the beam is simplified as a fired number of
rays and the averaged color of the hit polygons is recorded. For
other beams, their potentially visible sets (PVS) of polygons
are stored respectively. During an interactive walkthrough, the
visual information related to the current viewpoint is retrieved
from the storage. The view volume clipping, visibility culling
and detail simplification are efficiently supported by these
stored data. The rendering time is independent of the scene
complexity. },
}
@article{Bandi:1998:SDF,
author = {Srikanth Bandi and Daniel Thalmann},
title = {Space Discretization for Efficient Human
Navigation},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {195-206},
note = {{ISSN} 1067-7055},
keywords = {global navigation, dynamic programming, A* graph
search, articulated body models},
annote = {There is a large body of research on motion control
of legs in human models. However, they require specification of
olobal paths in which to move. A method for automatically
computing a global motion path for a human in {3D} environment of
obstacles is presented. Object space is discretized into a {3D}
grid of uniform cells and an optimal path is generated between
two points as a discrete cell path. The grid is treated as graph
with orthogonal links of uniform cost. A* search method is
applied for path finding. By considering only the cells on the
upper surface of objects on which human walks, a large portion
of the grid is discarded from the search space, thus boosting
efficiency. This is expected to be a higher level mechanism for
various local foot placement methods in human animation. },
}
@article{Streit:1998:IDH,
author = {L. M. Streit and J. W. Buchanan},
title = {Importance Driven Halftoning},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {207-218},
note = {{ISSN} 1067-7055},
keywords = {halftoning, bandpass pyramid, importance
function, limited resource rendering, non-photorealistic
rendering, traditional halftoning, drawing primitive,
multiresolution representations},
annote = {Most halftoning techniques have been primarily
concerned with achieving an accurate reproduction of local
grayscale intensities while avoiding the introduction of
artifacts. A second concern in halftoning has been the
preservation of edges in the halftoned image. In this paper we
will introduce a new halftoning technique that utilizes a
bandpass pyramid to achieve an accurate reproduction of
important attributes in the image. Ink is distributed through
the bandpass pyramidprimarily according to a user defined
importance function. This technique has three main
characteristics. First, our technique can produce results
similar to many other halftoning techniques by allowing a
generic importance function to be specified. If the chosen
importance function is average intensity we obtain results
similar to traditional halftoning. We also show how the
importance function can be changed to highlight areas with high
variance. Second, in addition to changing the
importancefunction, the drawing primitives can also be changed.
By using line segments instead of single pixels as drawing
primitives we illustrate how edge enhancement can be achieved.
Third, this technique allows the user to easily limit the number
drawing primitives used This is useful in limited resource
rendering. \\ In addition to providing a tailorable halftoning
technique our method can easily be adapted to produce two tone
non-photorealistic (NPR) images. We illustrate this by showing
how sketched effects can be achieved bv aligning the drawing
primitives according to different image attributes. },
}
@article{Buhmann:1998:DCQ,
author = {J. M. Buhmann and D. W. Fellner and M. Held and J.
Ketterer and J. Puzicha},
title = {Dithered Color Quantization},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {219-232},
note = {{ISSN} 1067-7055},
annote = {Image quantization and digital halftoning are
fundamental problems in computer graphics, which arise when
displaying high-color images on non-truecolor devices. Both
steps are generally performed sequentially and, in most cases,
independent of each other. Color quantization with a pixel-wise
defined distortion measure and the slithering process with its
local neighborhood optimize different quality criteria or,
frequently, follow a heuristic without reference to anv quality
measure. \\ In this paper we propose a new method to
simultaneously quantize and dither color images. The method is
based on a rigorous cost-function approach which optimizes a
quality criterion derived from a generic model of human
perception. A highly efficient algorithm for optimization based
on a multiscale method is developed for the dithered color
quantization cost function. The quality criterion and the
optimization algorithms are evaluated on a representative set of
artificial and real-world images as well as on a collection of
icons. A significant image quality improvement is observed
compared to standard color reduction approaches. },
}
@article{Neumann:1998:PBC,
author = {Laszlo O. Neumann and Kresimir Matkovic and Werner
Purgathofer},
title = {Perception Based Color Image Difference},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {233-242},
note = {{ISSN} 1067-7055},
annote = {A good image metric is often needed in digital
image synthesis. It can be used to check the convergence
behavior in progressive methods, to compare images rendered
using various rendering methods etc. Since images are rendered
to be observed by humans, an image metric should correspond to
human perception as well. We propose here a new algorithm which
operates in the original image space. There is no need for
Fourier or wavelet transforms. Furthermore the new metric is
view distance dependent. The new method uses the contrast
sensitivity function. The main idea is to place a number of
various rectangles in images, and to compute the {CIE} {LUV} average
color difference between corresponding rectangles. Errors are
then weighted according to the rectangle size and the contrast
sensitivity function. },
}
@article{Cohen-Or:1998:CVA,
author = {Daniel Cohen-Or and Gadi Fibich and Dan Halperin
and Eyal Zadicario},
title = {Conservative Visibility and Strong Occlusion for
Viewspace Partitioning of Densely Occluded Scenes},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {243-254},
note = {{ISSN} 1067-7055},
annote = {Computing the visibility of out-door scenes is
often much harder than of indoor scenes. A typical urban scene
for example, is densely occluded, and it is effective to
precompute its visibility space. since from a given point only a
small fraction of the scene is visible. A difficulty is that
although the majority of objects are hidden, some parts might be
visible at a distance in an arbitrary location, and it is not
clear how to detect them quickly. In this paper we presenta
method to partition the viewspace into cells containing a
conservative superset of the visible objects. For a given cell
the method tests the visibility of all the objects in the scene.
For each object it searches for a strong occluder which
guarantees that the object is not visible from any point within
the cell. We show analytically that in a densely occluded scene.
the vast majority of objects are strongly occluded. and the
overhead of rising conservative visibility (rather than
visibility) is small. These results are further supported by our
experimental results. We also analyze the cost of the method and
discuss its effectiveness. },
}
@article{Loos:1998:UWT,
author = {J. Loos and P. Slusallek and Hans-Peter Seidel},
title = {Using Wavefront Tracing for the Visualization and
Optimization of Progressive Lenses},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {255-266},
note = {{ISSN} 1067-7055},
annote = {Progressive addition lenses are a relatively new
approach to compensate for defects of the human visual system.
While traditional spectacles use rotationally symmetric lenses,
progressive lenses require the specification of free-form
surfaces. This poses difficult problems for the optimal design
and its visual evaluation. This paper presents two new
techniquesfor the visualization of optical systems and the
optimization ofprogressive lenses. Both are based on the same
wavefront tracing approach to accurately evaluate the refraction
properties of complex optical systems. \\ We use the results of
wavefront tracing for continuously re-focusing the eye during
rendering. Together with distribution ray tracing, this yields
high-quality images that accurately simulate the visual quality
of an optical system. The design of progressive lenses is
difficult due to the trade-off between the desired properties of
the lens and unavoidable optical errors, such as astigmatism and
distortions. We use wavefront tracing to derive an accurate
error functional describing the desired properties and the
optical error across a lens. Minimizing this error yields
optimal free-form lens surfaces. \\ While the basic approach is
much more general, in this paper, we describe its application to
the particular problem of designing and evaluating progressive
lenses and demonstrate the benefits of the new approach with
several example images. },
}
@article{Ai:1998:MDS,
author = {Zhuming Ai and Torsten Fr{\"{o}}hlich},
title = {Molecular Dynamics Simulation in Virtual
Environments},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {267-274},
note = {{ISSN} 1067-7055},
keywords = {virtual reality, molecular modeling, {CAVE},
molecular dynamics},
annote = {A virtual environment for interactive molecular
dynamics simulation has been designed and implemented at the
Fraunhofer Institute for Computer Graphics. Different kinds of
virtual reality devices are used in the environment for
immersive display and interaction with the molecular system. A
parallel computer is used to simulate the physical and chemical
properties of the molecular system dynamically. A high-speed
network exchanges data between the simulation program and the
modeling program. Molecular dynamics simulation virtual
environment provides scientists with a powerful tool to study
immersively the world of molecules. The dynamic interaction
between an {AIDS} antiviral drug and reverse transcriptase enzyme
is illustrated in the paper. },
}
@article{Zhu:1998:RBM,
author = {Qing-hong Zhu and Yan Chen and Arie Kaufman},
title = {Real-time Biomechanically-based Muscle Volume
Deformation using {FEM}},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {275-284},
note = {{ISSN} 1067-7055},
keywords = {voxel-based, biomechanically-based muscle
modeling, real-time muscle simulation, finite element method,
hierarchical representation, volume graphics, volumetric
deformation},
annote = {This paper presents a voxel-based biomechanical
model for muscle deformation using finite element method (FEM)
and volume graphics. Hierarchical voxel meshes are reconstructed
from filtered segmented muscle images followed by {FEM} simulation
and volume rendering. Physiological muscle force is considered
and linear elastic muscle models for both static and dynamic
cases are simulated by {FEM}. Voxel-based wireframe, polygon
surface rendering, and volume rendering techniques are applied
to show real-time muscle deformation processes as well as
realistic animations. },
}
@article{Roth:1998:ABB,
author = {S. H. Martin Roth and Markus H. Gross and Silvio
Turello and Friedrich R. Carls},
title = {A Bernstein-B{\'{e}}zier Based Approach to Soft
Tissue Simulation},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {285-294},
note = {{ISSN} 1067-7055},
keywords = {physically based modeling, finite element
methods, facial surgery simulation, facial modeling,
maxillofacial surgery, Bernstein-B{\'{e}} zier, soft tissue},
annote = {This paper discusses a Finite Element approachfor
volumetric soft tissue modeling in the context of facial surgery
simulation. We elaborate on the underlying physics and address
some computational aspects of the finite element discretization.
\\ In contrast to existing approaches speed is not our first
concern, but we strive for the highest possible accuracy of
simulation. We therefore propose an extension of linear
elasticity towards incompressibility and nonlinear material
behavior in order to describe the complex properties of human
soft tissue more accurately. Furthermore, we incorporate higher
order interpolation functions using a Bernstein-B{\'{e}}zier
formulation, which has various advantageous properties, such as
its integral polynomial form of arbitrary degree, efficient
subdivision schemes, and suitability for geometric modeling and
rendering. In addition, the use of tetrahedral Finite Elements
does not put any restriction on the geometry of the simulated
volumes. \\ Experimental results obtained from a synthetic block
of soft tissue and from the Visible Human Data Set illustrate
the performance of the envisioned model. },
}
@article{Koch:1998:EEU,
author = {Rolf M. Koch and Markus H. Gross and Albert
Bosshard},
title = {Emotion Editing using Finite Elements},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {295-302},
note = {{ISSN} 1067-7055},
keywords = {facial modeling, emotion editing},
annote = {This paper describes the prototype of a facial
expression editor. In contrast to evisting systems the presented
editor takes advantage of both medical datafor the simulation
and the consideration offacial anatomy during the definition of
muscle groups. The C1-continuous geometry and the high degree of
abstractionfor the expression editing sets this system apart
from others. Using finite elements we achieve a better precision
in comparison to particle systems. Furthermore, a precomputing
of facial action units enables us to compose facial expressions
by a superposition of facial action geometries in real-time. The
presented model is based on a generic facial model using a thin
plate and membrane approach for the surface and elastic springs
for facial tissue modeling. It has been used successfully for
performing facial surgery simulation. We illustrate features of
our system with examples from the Visible Human Dataset. },
}
@article{Weimer:1998:SSF,
author = {Henrik Weimer and Joe Warren},
title = {Subdivision Schemes for Thin Plate Splines},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {303-314},
note = {{ISSN} 1067-7055},
keywords = {surface modeling, variational design,
subdivision, thin plate splines, optimization, scattered data
interpolation, fair surfaces},
annote = {Thin plate splines are a well known entity of
geometric design. They are defined as the minimizer of a
variational problem whose differential operators approximate a
simple notion of bending energy. Therefore, thin plate splines
approximate surfaces with minimal bending energy and they are
widelv considered as the standard "fair" surface model. Such
surfaces are desired for many modeling and design applications.
\\ Traditionally, the way to construct such surfaces is to solve
the associated variationalproblem using finite elements or by
using analytic solutions based on radial basisfunctions. This
paper presents a novel approach for defining and computing thin
plate splines using subdivision methods. We present two
methodsfor the construction of thin plate splines based on
subdivision: A globally supported subdivision scheme which
exactly minimizes the energy functional as well as a family of
strictly local subdivision schemes which only utilize a small,
finite number of distinct subdivision rules and approcimately
solve the variational problem. A tradeoff between the accuracy
of the approximation and the locality of the subdivision scheme
is used to pick a particular member of this family of
subdivision schemes. \\ Later we show applications of these
approximating subdivision schemes to scattered data
interpolation and the design offair surfaces. In particular we
suggest an efficient methodology for finding control points for
the local subdivision scheme that will lead to an interpolating
limit surface and demonstrate how the schemes can be used for
the effective and efficient design of fair surfaces. },
}
@article{Krishnan:1998:RAA,
author = {S. Krishnan and M. Gopi and M. Lin and Dinesh
Manocha and A. Pattekar},
title = {Rapid and Accurate Contact Determination between
Spline Models using ShellTrees},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {315-326},
note = {{ISSN} 1067-7055},
annote = {In this paper, we present an efficient algorithm
for contact determination between spline models. We make use of
a new hierarchy, called ShellTree, that comprises of spherical
shells and oriented bounding boxes. Each spherical shell
corresponds to a portion of the volume between two concentric
spheres. Given large spline models, our algorithm decomposes
each surface into B{\'{e}}zier patches as part of preprocessing.
At runtime it dynamically computes a tight fitting axis-aligned
bounding box across each B{\'{e}}zier patch and efficiently
checks all such boxes for overlap. Using off-line and on-line
techniques for tree construction, our algorithm computes
ShellTrees for B{\'{e}}zier patches and performs fast overlap
tests between them to detect collisions. The overall approach
can trade off runtime performance for reduced memory
requirements. We have implemented the algorithm and tested it on
large models, each composed of hundred of patches. Its
performance varies with the configurations of the objects. For
many complex models composed of hundreds of patches, it can
accurately compute the contacts in a few milliseconds. },
}
@article{Zheng:1998:ANA,
author = {J. M. Zheng and K. W. Chan and I. Gibson},
title = {A New Approach for Direct Manipulation of Free-Form
Curve},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {327-334},
note = {{ISSN} 1067-7055},
annote = {There is an increasing demand for more intuitive
methods for creating and modifying free-form curves and surfaces
in {CAD} modeling systems. The methods should be based not only on
the change of the mathematical paraameters, such as control
points, knots, and weights, but also on the user's specified
constraints and shapes. This paper presents a new approach for
directly manipulating the shape of a free-form curve, leading to
a better control of the curve deformation and a more intuitive
CAD modeling interface. The user's intended deformation of a
curve is automatically converted into the modification of the
corresponding {NURBS} control points and knot sequence of the
curve. The algorithm for this approach includes curve elevation,
knot refinement, control point repositioning and knot removal.
Several examples shown in this paper demonstrate that the
proposed method can be used to deform a {NURBS} curve into the
desired shape. Currently, the algorithm concentrates on the
purely geometric consideration. Further work will include the
effect of material properties. },
}
@article{Theisel:1998:AES,
author = {Holger Theisel and Matthias Kreuseler},
title = {An Enhanced Spring Model for Information
Visualization},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {335-344},
note = {{ISSN} 1067-7055},
keywords = {information visualization, multidimensional
information space, spring model, free-form-surface},
annote = {In this paper we present a new technique for
visualizing multidimensional information. We describe objects of
a higher dimensional information space as small closed
free-form-surfaces in the visualization. The location, size and
shape of these surfaces describe the original objects in
information space uniquely. The underlying enhanced spring model
is introduced. The technique is applied to two test data sets.
},
}
@article{Howlett:1998:MSU,
author = {P. Howlett and W. T. Hewitt},
title = {Mass-Spring Simulation using Adaptive Non-Active
Points},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {345-354},
note = {{ISSN} 1067-7055},
keywords = {computer animation, dynamic simulation,
deformable bodies, mass-spring networks, adaptive non-active
points},
annote = {This paper introduces an adaptive component to a
mass-spring system as used in the modelling of cloth for
computer animation. The new method introduces non-active points
to the model which can adapt the shape of the cloth at
inaccuracies. This improves on conventional uniform mass-spring
systems by producing more visually pleasing results when
simulating the drape of cloth over irregular objects. The
computational cost of simulation is decreasd by reducing the
complexity of collision handling and enabling the use of coarser
mass-spring networks. },
}
@article{Meissner:1998:TAO,
author = {M. Mei{\ss}ner and B. Eberhardt},
title = {The Art of Knitted Fabrics, Realistic \& Physically
Based Modeling Of Knitted Fabrics},
volume = {17},
number = {3},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {355-362},
note = {{ISSN} 1067-7055},
keywords = {physically based modeling, textile modeling,
computer graphics, {3D} models},
annote = {In this paper we will present a system to use three
dimensional computer graphics in garment design. This system is
capable to visualize the "real", i.e. the physically correct,
appearance of a knitted fabric. A fast visualization of a
physically correct micro-structure garment is of crucial
importance in textile industry, since it enables fast and less
expensive product development. This system may be either used in
the design of new products or teaching the art of knitted
fabrics. We use in our system directly the produced machine-code
of the design system for knitting machines. A physical model, a
particle system, is used to calculate the dynamics of the
micro-structure of the knitted garment. },
}
@article{Holzschuch:1998:AEE,
author = {Nicolas Holzschuch and Fran{\c{c}}ois X. Sillion},
title = {An Exhaustive Error-Bounding Algorithm for
Hierarchical Radiosity},
volume = {17},
number = {4},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {197-218},
note = {{ISSN} 1067-7055},
annote = {This paper presents a complete algorithm for the
evaluation and control of error in radiosity calculations.
Providing such control is both extremely important for
industrial applications andd one of the most challenging issues
remaining in global illumination research. In order to control
the error, we need to estimate the accuracy of the calculation
while computing the energy exchanged between two objects. Having
this information for each radiosity interaction allows to
allocate more resources to refine interactions with greater
potential error, and to avoid spending more time to refine
interactions already represented with sufficient accuracy. Until
now, the accuracy of the computed energy exchange could only be
approximated using heuristic algorithms. This paper presents the
first exhaustive algorithm to compute fully reliable upper and
lower bounds on the energy being exchanged in each interaction.
This is accomplished by computing first and second derivatives
of the radiosity function where appropriate, and making use of
two concavity conjectures. These bounds are then used in a
refinement criterion for hierarchical radiosity, resulting in a
global illumination algorithm with complete control of the error
incurred. Results are presented, demonstrating the possibility
to create radiosity solutions with guaranteed precision. We then
extend our algorithm to consider linear bounding functions
instead of constant functions, thus creating simpler meshes in
regions where the function is concave, without loss of
precision. Our experiments show that the computation of
radiosity derivatives along with the radiosity values only
requires a modest extra cost, with the advantage of a much
greater precision. },
}
@article{Duce:1998:RMF,
author = {D. A. Duce and D. Giorgetti and C. S. Cooper and J.
R. Gallop and I. J. Johnson and E. Robinson and C. D. Seelig},
title = {Reference Models for Distributed Cooperative
Visualization},
volume = {17},
number = {4},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {219-233},
note = {{ISSN} 1067-7055},
annote = {In this paper reference models for visualization
systems that have appeared in the literature are surveyed and a
new reference model for distributed cooperative visualization
developed in the {MANICORAL} project (funded by the {EU} Telematics
Programme) is described. The relationship of earlier models to
the new model is discussed. A number of cooperative
visualization systems that have been reported in the literature
are compared in the framework of the {MANICORAL} model. },
}
@article{Neumann:1998:ILM,
author = {L{\'{a}}szl{\'{o}} Neumann and Kresmir Matkovic and
Attila Neumann and Werner Purgathorer},
title = {Incident Light Metering in Computer Graphics},
volume = {17},
number = {4},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {235-247},
note = {{ISSN} 1067-7055},
annote = {Every rendering process consists of two steps. The
first is the computing of luminance values by methods like ray
tracing or radiosity, and the second step is the mapping of the
computed values to values appropriate for displaying. In the
last years, as alternative to simple linear scaling which maps
the average value to the medium luminance, some new ways of
mapping were introduced. These new methods are based on
photography analogies and on human vision models. All existing
methods follow, implicitly or explicitly, the reflected light
metering principle. The method introduced in this paper is the
first that follows the incident light metering used in
professional photography and in the movie industry. Actually the
irradiances are measured using a set of diffusors, which are
placed automatically in the scene, and a linear scale factor
based on these measurements is used to map the computed
radiances to the display device. The diffusors act as half space
integrators, they collect the light energy from all half space
directions. The light comes from the primary light sources, or
it is the result of various interreflections. The newly
introduced method reproduces original colors faithfully even for
scenes with very low or very high average reflectivity. },
}
@article{Duke:1998:PPI,
author = {D. J. Duke and I. Herman},
title = {Programming Paradigms in an Object-Oriented
Multimedia Standard},
volume = {17},
number = {4},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {249-261},
note = {{ISSN} 1067-7055},
annote = {Of the various programming paradigms in use today,
object-orientation is probably the most successful in terms of
industrial take-up and application, particularly in the field of
multimedia. It is therefore unsurprising that this technology
has been adopted by {ISO}/IEC {JTC1}/SC24 as the foundation for a
forthcoming International Standard for Multimedia, called {PREMO}.
Two important design aims of {PREMO} are that it be distributable,
and that it provides a set of media-related services that can be
extended in a disciplined way to support the needs of future
applications and problem domains. While key aspects of the
object-oriented paradigm provide a sound technical basis for
achieving these aims, the need to balance extensibility and a
high-level programming interface against the realities of
efficiency and ease of implementation in a distributed setting
meant that the task of synthesising a Standard from existing
practice was non-trivial. Indeed, in order to meet the design
aims of {PREMO} is was found necessary to augment the basic object
infrastructure with facilities and ideas drawn from other
programming paradigms, in particular concepts from constraint
management and data flow. This paper describes the important
trade-offs that have affected the development of {PREMO} and
explains how these are addressed through the use of specific
programming paradigms. },
}
@article{Brun:1998:AFA,
author = {L. Brun and C. Secroun},
title = {A Fast Algorithm for Inverse Colormap Computation},
volume = {17},
number = {4},
journal = {Computer Graphics Forum},
year = {1998},
editor = {N. Ferreira and M. G{\"{o}}bel},
publisher = {Blackwell Publishers},
pages = {261-271},
note = {{ISSN} 1067-7055},
annote = {The inverse colormap operation is the process which
allows an image to be displayed with a limited set of colors. In
order to obtain a minimal visual distortion between the input
image annd the one displayed, inverse colormap algorithms
associate each color with its nearest representative. The method
presented in this paper is carried out in two steps. First, the
3D Voronoi diagram implicitly used by inverse colormap
algorithms is approximated using a Karhunen-Lo{\`{e}}ve
transformation. Then, a correcting step is carried out in order
to reduce the influence of the first approximation. The
complexity of our algorithm is independent of the size of the
colormap. Moreover, its results are equal or quite close to the
optimal solution. },
}
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