%M C.VRST.04.1
%T Recent advances in visibility determination for large and complex virtual
environments
%S Keynote speaker
%A Cohen-Or, Daniel
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 1
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077554
%X Rendering large and complex virtual environments in real time remains a
challenge as the complexity of models keeps growing. Visibility techniques such
as occlusion culling can effectively reduce the rendering depth complexity.
   In my talk I'll survey recent advances in visibility determination. I'll
focus on conservative and aggressive techniques and show how these techniques
can be combined effectively with level of details and image-based techniques.
I'll show how these new techniques can be accelerated by modern graphics cards
to achieve interactive rendering of extremely complex scenes.

%M C.VRST.04.2
%T Fast and reliable collision culling using graphics hardware
%S Session 1A: object interactions and collisions
%A Govindaraju, Naga K.
%A Lin, Ming C.
%A Manocha, Dinesh
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 2-9
%K collision detection, deformable models, graphics hardware, minkowski sums
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077538
%X We present a reliable culling algorithm that enables fast and accurate
collision detection between triangulated models in a complex environment. Our
algorithm performs fast visibility queries on the GPUs for eliminating a subset
of primitives that are not in close proximity. To overcome the accuracy
problems caused by the limited viewport resolution, we compute the Minkowski
sum of each primitive with a sphere and perform reliable 2.5D overlap tests
between the primitives. We are able to achieve more effective collision culling
as compared to prior object-space culling algorithms. We integrate our culling
algorithm with CULLIDE [8] and use it to perform reliable GPU-based collision
queries at interactive rates on all types of models, including non-manifold
geometry, deformable models, and breaking objects.

%M C.VRST.04.10
%T Interactive collision detection for complex and deformable models using
programmable graphics hardware
%S Session 1A: object interactions and collisions
%A Chen, Wei
%A Wan, Huagen
%A Zhang, Hongxin
%A Bao, Hujun
%A Peng, Qunsheng
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 10-15
%K collision detection, deformation, graphics hardware, voxelization
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077539
%X In this paper we present an interactive collision detection algorithm for
complex and deformable objects. For two target models, our approach rapidly
calculates their region of interests (ROI), which is the overlapping of their
axis aligned bounding boxes (AABBs), in CPU. The surfaces of both models inside
the ROI are then voxelized using a novel GPU-based real-time voxelization
method. The resultant volumes are represented by two 2D textures in video
memory. The collision query is efficiently accomplished by comparing these 2D
textures in GPU. The algorithm is robust to handle arbitrary shapes, no matter
geometric models are convex or concave, closed or open, rigid or deformable.
Our preliminary implementation achieves interactive frame rate for complex
models with up to one million triangles on commodity desktop PCs.

%M C.VRST.04.16
%T The Grappl 3D interaction technique library
%S Session 1A: object interactions and collisions
%A Green, Mark
%A Lo, Joe
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 16-23
%K 3D user interfaces, interaction techniques
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077540
%X One of the obstacles to the widespread use of interactive 3D applications is
the lack of good tools for developing them. The development of these tools has
been complicated by the wide range of hardware configurations used in 3D
applications. Also, there is a lack of common software platforms for developing
the tools required for 3D user interfaces. As a result, many groups develop
their own set of interaction techniques without taking advantage of the work of
others, wasting a considerable amount of development time. The Grappl project
aims to solve these problems by providing software tools that adapt to the
hardware configuration and automatically design most of the user interface. One
of the main components of this project is an interaction technique library that
supports a wide range of input and output devices. This library provides an
open platform for the development of 3D interaction techniques that encourages
further development in this area. Interaction techniques developed using this
toolkit can be used in our user interface design system, so application
developers can easily take advantage of new interaction techniques. The design
and implementation of this library is described in this paper.

%M C.VRST.04.24
%T Multi-layered deformable surfaces for virtual clothing
%S Session 1A: object interactions and collisions
%A Wong, Wingo Sai-Keung
%A Baciu, George
%A Hu, Jinlian
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 24-31
%K collision detection, deformable surfaces, master-slave, multi-layer,
non-manifold geometry, virtual clothing
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077541
%X We propose a positional constraint method to solve the multi-layered
deformable surface problem based on a master-slave scheme. This allows two or
more deformable surfaces to be attached together in any orientation relative to
each other for the purpose of modeling cloth attachments and multi-layered
clothing. The method does not require the mesh resolution of the deformable
surfaces to be the same or the matching of anchor points between layers. After
the attachment process, the surfaces are treated as a multi-layered surface.
However, this surface contains non-manifold features. We introduce a technique
for preventing self-intersection of the non-manifold features. We demonstrate
the stability of this method by performing several experiments with high
surface complexity and a large number of colliding feature pairs. Interactive
rates can easily be achieved for multilayered surfaces with an appropriate
discretization level of triangles.

%M C.VRST.04.32
%T Animating reactive motions for biped locomotion
%S Session 1A: object interactions and collisions
%A Komura, Taku
%A Leung, Howard
%A Kuffner, James
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 32-40
%K interactive 3D graphics, inverse kinematics, motion control
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077542
%X In this paper, we propose a new method for simulating reactive motions for
running or walking human figures. The goal is to generate realistic animations
of how humans compensate for large external forces and maintain balance while
running or walking. We simulate the reactive motions of adjusting the body
configuration and altering footfall locations in response to sudden external
disturbance forces on the body. With our proposed method, the user first
imports captured motion data of a run or walk cycle to use as the primary
motion. While executing the primary motion, an external force is applied to the
body. The system automatically calculates a reactive motion for the center of
mass and angular momentum around the center of mass using an enhanced version
of the linear inverted pendulum model. Finally, the trajectories of the
generalized coordinates that realize the precalculated trajectories of the
center of mass, zero moment point, and angular momentum are obtained using
constrained inverse kinematics. The advantage of our method is that it is
possible to calculate reactive motions for bipeds that preserve dynamic balance
during locomotion, which was difficult using previous techniques. We
demonstrate our results on an application that allows a user to interactively
apply external perturbations to a running or walking virtual human model. We
expect this technique to be useful for human animations in interactive 3D
systems such as games, virtual reality, and potentially even the control of
actual biped robots.

%M C.VRST.04.41
%T Animating complex hairstyles in real-time
%S Session 1B: animation and simulations
%A Volino, Pascal
%A Magnenat-Thalmann, Nadia
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 41-48
%K hair modeling, mechanical simulation, real-time animation, virtual
characters
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077544
%X True real-time animation of complex hairstyles on animated characters is the
goal of this work, and the challenge is to build a mechanical model of the
hairstyle which is sufficiently fast for real-time performance while preserving
the particular behavior of the hair medium and maintaining sufficient
versatility for simulating any kind of complex hairstyles.
   Rather than building a complex mechanical model directly related to the
structure of the hair strands, we take advantage of a volume free-form
deformation scheme. We detail the construction of an efficient lattice
mechanical deformation model which represents the volume behavior of the hair
strands. The lattice is deformed as a particle system using state-of-the-art
numerical methods, and animates the hairs using quadratic B-Spline
interpolation. The hairstyle reacts to the body skin through collisions with a
metaball-based approximation. The model is highly scalable and allows
hairstyles of any complexity to be simulated in any rendering context with the
appropriate tradeoff between accuracy and computation speed, fitting the need
of Level-of-Detail optimization schemes.

%M C.VRST.04.49
%T A lightweight algorithm for real-time motion synthesis
%S Session 1B: animation and simulations
%A Kawachi, Katsuaki
%A Kanade, Takeo
%A Suzuki, Hiromasa
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 49-56
%K character animation, inverse kinematics
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077545
%X This paper presents an algorithm for interactive character animation with
kinematic constraints with limited computational time. In order to reduce
necessary computation, the animation is not created by procedural algorithm but
synthesized by deforming and concatenating short motion examples, each
consisting of a sequence of postures. A keyframe placed between two consecutive
motion examples is deformed by using inverse kinematics so that it satisfies
given constraints. The motion examples between the keyframes are deformed to
ensure continuity of postures in position and velocity. We parameterize each
posture as a set of particles in an orthogonal coordinate system. The inverse
kinematics method with the particle representation realizes fast and stable
deformation of keyframe postures, and the deformation of motion examples are
calculated on a frame-by-frame basis by decomposing a whole-body deformation
into per-particle deformations. We present some examples of character
animations synthesized at an interactive rate by this algorithm.

%M C.VRST.04.57
%T Marker-free kinematic skeleton estimation from sequences of volume data
%S Session 1B: animation and simulations
%A Theobalt, Christian
%A de Aguiar, Edilson
%A Magnor, Marcus A.
%A Theisel, Holger
%A Seidel, Hans-Peter
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 57-64
%K kinematic skeleton, learning, model reconstruction, motion capture,
tracking, volume processing
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077546
%X For realistic animation of an artificial character a body model that
represents the character's kinematic structure is required. Hierarchical
skeleton models are widely used which represent bodies as chains of bones with
interconnecting joints. In video motion capture, animation parameters are
derived from the performance of a subject in the real world. For this
acquisition procedure too, a kinematic body model is required. Typically, the
generation of such a model for tracking and animation is, at best, a
semi-automatic process. We present a novel approach that estimates a
hierarchical skeleton model of an arbitrary moving subject from sequences of
voxel data that were reconstructed from multi-view video footage. Our method
does not require a-priori information about the body structure. We demonstrate
its performance using synthetic and real data.

%M C.VRST.04.65
%T Scalable pedestrian simulation for virtual cities
%S Session 1B: animation and simulations
%A Stylianou, Soteris
%A Fyrillas, Marios M.
%A Chrysanthou, Yiorgos
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 65-72
%K animation, avatars, pedestrian simulation
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077547
%X Most of the common approaches for the pedestrian simulation, used in the
Graphics/VR community, are bottom-up. The avatars are individually simulated in
the space and the overall behavior emerges from their interactions. This can
lead to interesting results but it does not scale and can not be applied to
populating a whole city. In this paper we present a novel method that can scale
to a scene of almost any size. We use a top-down approach where the movement of
the pedestrians is computed at a higher level, taking a global view of the
model, allowing the flux and densities to be maintained at very little cost at
the city level. This information is used for stochastically guiding a more
detailed and realistic low level simulation when the user zooms in to a
specific region, thus maintaining the consistency.
   At the heart of the system is an iterative method that models the flow of
avatars as a random walk. People are moved around a graph of nodes until the
model reaches a steady state which provides feedback for the avatar low level
navigation at run time. The Negative Binomial distribution function is used to
model the number of people leaving each node while the selected direction is
based on the popularity of the nodes through their preference-factor. The
preference-factor is a function of a number of parameters including the
visibility of a node, the events taking place in it and so on.
   An important feature of the low-level dynamics is that a user can
interactively specify a number of intuitive variables that can predictably
modify the collective behavior of the avatars in a region; the density, the
flux and the number of people can be selectively modified.

%M C.VRST.04.73
%T Observing effects of attention on presence with fMRI
%S Session 1C: human interactions and perceptions
%A Lee, Sungkil
%A Kim, Gerard J.
%A Lee, Janghan
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 73-80
%K attention, fMRI, presence, virtual reality
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077549
%X Presence is one of the goals of many virtual reality systems. Historically,
in the context of virtual reality, the concept of presence has been associated
much with spatial perception (bottom up process) as its informal definition of
"feeling of being there" suggests. However, recent studies in presence have
challenged this view and attempted to widen the concept to include
psychological immersion, thus linking more high level elements (processed in a
top down fashion) to presence such as story and plots, flow, attention and
focus, identification with the characters, emotion, etc. In this paper, we
experimentally studied the relationship between two content elements, each
representing the two axis of the presence dichotomy, perceptual cues for
spatial presence and sustained attention for (psychological) immersion. Our
belief was that spatial perception or presence and a top down processed concept
such as voluntary attention have only a very weak relationship, thus our
experimental hypothesis was that sustained attention would positively affect
spatial presence in a virtual environment with impoverished perceptual cues,
but have no effect in an environment rich in them. In order to confirm the
existence of the sustained attention in the experiment, fMRI of the subjects
were taken and analyzed as well. The experimental results showed that that
attention had no effect on spatial presence, even in the environment with
impoverished spatial cues.

%M C.VRST.04.81
%T Supporting social human communication between distributed walk-in displays
%S Session 1C: human interactions and perceptions
%A Roberts, David
%A Wolff, Robin
%A Otto, Oliver
%A Kranzlmueller, Dieter
%A Anthes, Christoph
%A Steed, Anthony
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 81-88
%K CVE, consistency control, event traffic, human interaction
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077550
%X Future teleconferencing may enhance communication between remote people by
supporting non-verbal communication within an unconstrained space where people
can move around and share the manipulation of artefacts. By linking walk-in
displays with a Collaborative Virtual Environment (CVE) platform we are able to
physically situate a distributed team in a spatially organised social and
information context. We have found this to demonstrate unprecedented
naturalness in the use of space and body during non-verbal communication and
interaction with objects.
   However, relatively little is known about how people interact through this
technology, especially while sharing the manipulation of objects. We observed
people engaged in such a task while geographically separated across national
boundaries. Our analysis is organised into collaborative scenarios, that each
requires a distinct balance of social human communication with consistent
shared manipulation of objects.
   Observational results suggest that walk-in displays do not suffer from some
of the important drawbacks of other displays. Previous trials have shown that
supporting natural non-verbal communication, along with responsive and
consistent shared object manipulation, is hard to achieve. To better understand
this problem, we take a close look at how the scenario impacts on the
characteristics of event traffic. We conclude by suggesting how various
strategies might reduce the consistency problem for particular scenarios.

%M C.VRST.04.89
%T Using a vibro-tactile display for enhanced collision perception and presence
%S Session 1C: human interactions and perceptions
%A Ryu, Jonghyun
%A Kim, Gerard Jounghyun
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 89-96
%K multimodality, presence, sensory saltation, tactile interface, vibration
feedback model, vibrator, virtual environments
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077551
%X One of the goals and means of realizing virtual reality is through
multimodal interfaces, leveraging on the many sensory organs that humans
possess. Among them, the tactile sense is important and useful for close range
interaction and manipulation tasks. In this paper, we explore this possibility
using a vibro-tactile device on the whole body for simulating collision between
the user and virtual environment. We first experimentally verify the effect of
enhanced user felt presence by employing localized vibration feedback alone on
collision, and further investigate how to effectively provide the sense of
collision using the vibro-tactile display in different ways. In particular, we
test the effects of using a vibration feedback model (for simulating collision
with different object materials), saltation, and simultaneous use of 3D sound
toward spatial presence and perceptual realism. The results have shown that
employing the proposed vibro-tactile interface did enhance the sense of
presence, especially when combined with 3D sound. Furthermore, the use of
saltation also helped the user detect and localize the point of contact more
correctly. The use of the vibration feedback model was not found to be
significantly effective, and sometimes even hindered the correct sense of
collision primarily due to the limitation of the vibrotactile display device.

%M C.VRST.04.97
%T FreeWalk/Q: social interaction platform in virtual space
%S Session 1C: human interactions and perceptions
%A Nakanishi, Hideyuki
%A Ishida, Toru
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 97-104
%K agent, avatar, interaction platform, scenario description, social
interaction, virtual city, virtual community, virtual space, virtual training
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077552
%X We have integrated technologies related to virtual social interaction, e.g.
virtual environments, visual simulations, and lifelike characters. In our
previous efforts to integrate them, the asymmetry between agents and avatars
made the systems too complex to be used widely. Another crucial problem we
faced is that it took a long time to construct agents that play various roles,
since each role needs its specific behavioral repertory. To eliminate these
problems, we developed a general-use platform, FreeWalk/Q, in which agents and
avatars can share the same interaction model and scenario. We created a control
mechanism to reduce the behavioral differences between agents and avatars, and
a description method to design the external role rather than the internal
mechanism. In the development, we found that it was necessary to prepare
several topologies of control mechanism and several granular levels of
description method.

%M C.VRST.04.105
%T Turning VR inside out: thoughts about where we are heading
%S Keynote speaker
%A Feiner, Steven
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 105
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077536
%X Our field and the world have changed greatly in the ten years since the
first VRST was held in Singapore in 1994. Computers have grown smaller, faster,
and cheaper, while polygon counts, frame rates, and display resolutions have
increased impressively, true to the promise of Moore's Law. But, what comes
next?
   This talk will sketch some of the directions in which I feel virtual reality
is (or should be) heading. I will discuss the potential for taking virtual
reality outside, through wearable and mobile computing; for bring the outside
in, by capturing the real world; and for accommodating large numbers of
displays, users, and tasks, by embedding them in a fluid and collaborative
augmented environment.

%M C.VRST.04.106
%T Scanning and rendering scene tunnels for virtual city traversing
%S Session 2A: applications and systems
%A Zheng, Jiang Yu
%A Zhou, Yu
%A Shi, Min
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 106-113
%K internet media, navigation, route panorama, scene representation, scene
tunnel, visualization
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077556
%X This paper proposes a visual representation named scene tunnel to capture
and visualize urban scenes for Internet based virtual city traversing. We scan
cityscapes by using multiple cameras on a vehicle that moves along a street,
and generate a real scene archive more complete than a route panorama. The
scene tunnel can cover high architectures and various object aspects, and its
data size is much less than video. It is suitable for image transmission and
rendering over the Internet. The scene tunnel has a uniformed resolution along
the camera path and can provide continuous views for visual navigation in a
virtual or real city. This paper explores the image acquisition methods from
slit calibration, view scanning, to image integration. A plane of scanning is
determined for flexible camera setting and image integration. The paper further
addresses the city visualization on the Internet that includes view
transformation, data streaming, and interactive functions. The high-resolution
scenes are mapped onto a wide window dynamically. The compact and continuous
scene tunnel facilitates the data streaming and allows virtual traversing to be
extended to a large area.

%M C.VRST.04.114
%T Modeling and rendering of walkthrough environments with panoramic images
%S Session 2A: applications and systems
%A Siu, Angus M. K.
%A Wan, Ada S. K.
%A Lau, Rynson W. H.
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 114-121
%K 3D reconstruction, geometric proxy, image-based methods, image-based
modeling, image-based rendering
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077557
%X An important, potential application of image-based techniques is to create
photo-realistic image-based environments for interactive walkthrough. However,
existing image-based studies are based on different assumptions with different
focuses. There is a lack of a general framework or architecture for evaluation
and development of a practical image-based system. In this paper, we propose an
architecture to unify different image-based methods. Based on the architecture,
we propose an image-based system to support interactive walkthrough of scalable
environments. In particular, we introduce the concept of angular range, which
is useful for designing a scalable configuration, recovering geometric proxy as
well as rendering. We also propose a new method to recover geometry information
even from outdoor scenes and a new rendering method to address the problem of
abrupt visual changes in a scalable environment.

%M C.VRST.04.122
%T Design and evaluation of a wind display for virtual reality
%S Session 2A: applications and systems
%A Moon, Taeyong
%A Kim, Gerard J.
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 122-128
%K air flow, interface, presence, simulation, virtual environments, wind
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077558
%X One of the goals in the design of virtual environments (VE) is to give the
user the feeling of existence within the VE, known as presence. Employing
multimodality is one way to increase presence, and as such, numerous multimodal
input and output devices have been used in the context of virtual reality (VR).
However, the simulation and investigation into the effects of the wind (or air
flow) has not been treated much in the VR research community. In this paper, we
introduce a wind display system, called the "WindCube," designed for virtual
reality applications. The WindCube consists of a number of small fans attached
to a cubical structure in which a VR system user interacts with the VE. We
first discuss the design parameters of the proposed display device such as the
type of the fan used, and the appropriate number, locations and directions of
the fans in relation to providing the minimum level of the wind effects and
enhanced presence. In order to simulate the effects of the wind, a wind field
is first specified within the virtual environment. We describe how the
specified wind field is rendered to the user through the proposed device.
Finally, we investigate the effects of the proposed wind display to user felt
presence through an experiment. It is our belief that wind display is very
important and cost effective modality to consider and employ, because it
involves "air," a medium that makes the VE felt more "livable," in contrast to
many VE's that looks vacuum.

%M C.VRST.04.129
%T GameOD: an internet based game-on-demand framework
%S Session 2A: applications and systems
%A Li, Frederick W. B.
%A Lau, Rynson W. H.
%A Kilis, Danny
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 129-136
%K distributed synchronization, distributed virtual environments, multiplayer
online games, on-demand replication
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077559
%X Multiplayer online 3D games are becoming very popular in recent years.
However, existing games require the complete game content to be installed prior
to game playing. Since the content is usually large in size, it may be
difficult to run these games on a PDA or other handheld devices. It also pushes
game companies to distribute their games as CDROMs/DVDROMs rather than online
downloading. On the other hand, due to network latency, players may perceive
discrepant status of some dynamic game objects. In this paper, we present a
game-on-demand (GameOD) framework to distribute game content progressively in
an on-demand manner. It allows critical contents to be available at the
players' machines in a timely fashion. We present a simple distributed
synchronization method to allow concurrent players to synchronize their
perceived game status. Finally, we show some performance results of the
proposed framework.

%M C.VRST.04.137
%T A CAVE system for interactive modeling of global illumination in car
interior
%S Session 2A: applications and systems
%A Dmitriev, Kirill
%A Annen, Thomas
%A Krawczyk, Grzegorz
%A Myszkowski, Karol
%A Seidel, Hans-Peter
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 137-145
%K BRDF, CAVE, LCD panel, virtual reality
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077560
%X Global illumination dramatically improves realistic appearance of rendered
scenes, but usually it is neglected in VR systems due to its high costs. In
this work we present an efficient global illumination solution specifically
tailored for those CAVE applications, which require an immediate response for
dynamic light changes and allow for free motion of the observer, but involve
scenes with static geometry. As an application example we choose the car
interior modeling under free driving conditions. We illuminate the car using
dynamically changing High Dynamic Range (HDR) environment maps and use the
Precomputed Radiance Transfer (PRT) method for the global illumination
computation. We leverage the PRT method to handle scenes with non-trivial
topology represented by complex meshes. Also, we propose a hybrid of PRT and
final gathering approach for high-quality rendering of objects with complex
Bi-directional Reflectance Distribution Function (BRDF). We use this method for
predictive rendering of the navigation LCD panel based on its measured BRDF.
Since the global illumination computation leads to HDR images we propose a tone
mapping algorithm tailored specifically for the CAVE. We employ head tracking
to identify the observed screen region and derive for it proper luminance
adaptation conditions, which are then used for tone mapping on all walls in the
CAVE. We distribute our global illumination and tone mapping computation on all
CPUs and CPUs available in the CAVE, which enables us to achieve interactive
performance even for the costly final gathering approach.

%M C.VRST.04.146
%T Towards full-body haptic feedback: the design and deployment of a
spatialized vibrotactile feedback system
%S Session 2B: real-time interactions and rendering (short papers)
%A Lindeman, Robert W.
%A Page, Robert
%A Yanagida, Yasuyuki
%A Sibert, John L.
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 146-149
%K CQB, full-body, haptic feedback, virtual reality
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077562
%X This paper presents work we have done on the design and implementation of an
untethered system to deliver haptic cues for use in immersive virtual
environments through a body-worn garment. Our system can control a large number
of body-worn vibration units, each with individually controllable vibration
intensity. Several design iterations have helped us to refine the system and
improve such aspects as robustness, ease of donning and doffing, weight, power
consumption, cable management, and support for many different types of feedback
units, such as pager motors, solenoids, and muffin fans. In addition,
experience integrating the system into an advanced virtual reality system has
helped define some of the design constraints for creating wearable solutions,
and to further refine our implementation.

%M C.VRST.04.150
%T An efficient representation of complex materials for real-time rendering
%S Session 2B: real-time interactions and rendering (short papers)
%A Ma, Wan-Chun
%A Chao, Sung-Hsiang
%A Chen, Bing-Yu
%A Chang, Chun-Fa
%A Ouhyoung, Ming
%A Nishita, Tomoyuki
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 150-153
%K bi-directional texture function, parametric shading function, reflectance
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077563
%X In this paper, we propose an appearance representation for general complex
materials which can be applied in real-time rendering framework. By combining a
single parametric shading function (such as the Phong model) and the proposed
spatial-varying residual function (SRF), this representation can recover the
appearance of complex materials with little loss of visual fidelity. The
difference between the real data and the parametric shading is directly fitted
by a specific function for easy reconstruction. It is simple, flexible and easy
to be implemented on programmable graphics hardware. Experiments show that the
mean square error (MSE) between the reconstructed appearance and real
photographs is less than 5%.

%M C.VRST.04.154
%T Huge texture mapping for real-time visualization of large-scale terrain
%S Session 2B: real-time interactions and rendering (short papers)
%A Hua, Wei
%A Zhang, Huaisheng
%A Lu, Yanqing
%A Bao, Hujun
%A Peng, Qunsheng
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 154-157
%K mipmap, out-of-core, real-time rendering, terrain, texture compression,
texture mapping
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077564
%X Texture mapping greatly influences the performance of visualization in many
3D applications. Sometimes the texture data is so large that it has to be
stored in slower external storage, rather than fast texture memory or host
memory. In these circumstances, texture mapping becomes the performance
bottleneck. In this paper, we present a compact multiresolution model, Texture
Mipmap Quadtree (TMQ), to represent large-scale textures. It facilitates fast
loading and pre-filtering of textures from slower external storage. Integrating
continuous LOD model of terrain geometry, we present a criterion to select
proper textures from TMQ according to viewing parameters during rendering
stage. By exploiting temporal coherence, a dynamic texture management scheme is
devised based on two-level cache hierarchy to further increase the performance
of texture mapping.

%M C.VRST.04.158
%T A voxel based multiresolution technique for soft tissue deformation
%S Session 2B: real-time interactions and rendering (short papers)
%A Lenka Jeřábková, A
%A Kuhlen, Torsten
%A Wolter, Timm P.
%A Pallua, Norbert
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 158-161
%K finite elements method, multiresolution, soft tissue deformation, virtual
reality
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077565
%X Real time tissue deformation is an important aspect of interactive virtual
reality (VR) environments such as medical trainers. Most approaches in
deformable modelling use a fixed space discretization. A surgical trainer
requires high plausibility of the deformations especially in the area close to
the instrument. As the area of intervention is not known a priori, adaptive
techniques have to be applied.
   We present an approach for real time deformation of soft tissue based on a
regular FEM mesh of cube elements as opposed to a mesh of tetrahedral elements
used by the majority of soft tissue simulators. A regular mesh structure
simplifies the local refinement operation as the elements topology and
stiffness are known implicitly. We propose an octree-based adaptive
multiresolution extension of our basic approach.
   The volumetric representation of the deformed object is created
automatically from medical images or by voxelization of a surface model. The
resolution of the volumetric representation is independent of the surface
geometry resolution. The surface is deformed according to the simulation
performed on the underlying volumetric mesh.

%M C.VRST.04.162
%T A framework for 3D visualisation and manipulation in an immersive space
using an untethered bimanual gestural interface
%S Session 2B: real-time interactions and rendering (short papers)
%A Boussemart, Yves
%A Rioux, François
%A Rudzicz, Frank
%A Wozniewski, Michael
%A Cooperstock, Jeremy R.
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 162-165
%K bimanual interaction, gesture recognition, immersive environment, scene
modelling, telepresence, toolglass
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077566
%X Immersive Environments offer users the experience of being submerged in a
virtual space, effectively transcending the boundary between the real and
virtual world. We present a framework for visualization and manipulation of 3D
virtual environments in which users need not resort to the awkward command
vocabulary of traditional keyboard-and-mouse interaction. We have adapted the
transparent toolglass paradigm as a gestural interface widget for a spatially
immersive environment. To serve that purpose, we have implemented a bimanual
gesture interpreter to recognize and translate a user's actions into commands
for control of these widgets. In order to satisfy a primary design goal of
keeping the user completely untethered, we use purely video-based tracking
techniques.

%M C.VRST.04.166
%T The MORGAN framework: enabling dynamic multi-user AR and VR projects
%S Session 2C: techniques and applications (short papers)
%A Ohlenburg, Jan
%A Herbst, Iris
%A Lindt, Irma
%A Fröhlich, Thorsten
%A Broll, Wolfgang
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 166-169
%K augmented reality, distributed system design, framework, render engine,
tracking, virtual reality
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077568
%X The availability of a suitable framework is of vital importance for the
development of Augmented Reality (AR) and Virtual Reality (VR) projects. While
features such as scalability, platform independence, support of multiple users,
distribution of components, and an efficient and sophisticated rendering are
the key requirements of current and future applications, existing frameworks
often address these issues only partially. In our paper we present MORGAN -- an
extensible component-based AR/VR framework, enabling sophisticated dynamic
multi-user AR and VR projects. Core components include the MORGAN API,
providing developers access to various input devices, including common tracking
devices, as well as a modular render engine concept, allowing us to provide
native support for individual scene graph concepts. The MORGAN framework has
already been successfully deployed in several national and international
research and development projects.

%M C.VRST.04.170
%T Fast model tracking with multiple cameras for augmented reality
%S Session 2C: techniques and applications (short papers)
%A Sanson, Alberto
%A Castellani, Umberto
%A Fusiello, Andrea
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 170-173
%K exterior orientation, pose estimation, registration
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077569
%X In this paper we present a technique for tracking complex models in video
sequences with multiple cameras. Our method uses information derived from image
gradient by comparing them with edges of the tracked object, whose 3D model is
known. A score function is defined, depending on the amount of image gradient
"seen" by the model edges. The sought pose parameters are obtained by
maximizing this function using a non deterministic algorithm which proved to be
optimal for this problem. Preliminary experiments with both synthetic and real
sequences have shown small errors in pose estimations and a good behavior in
augmented reality applications.

%M C.VRST.04.174
%T Occlusion handling for medical augmented reality using a volumetric phantom
model
%S Session 2C: techniques and applications (short papers)
%A Fischer, Jan
%A Bartz, Dirk
%A Straßer, Wolfgang
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 174-177
%K augmented reality, occlusion handling, visual hull, volume data
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077570
%X The support of surgical interventions has long been in the focus of
application-oriented augmented reality research. Modern methods of surgery,
like minimally-invasive procedures, can benefit from the additional information
visualization provided by augmented reality. The usability of medical augmented
reality depends on a rendering scheme for virtual objects designed to generate
easily and quickly understandable augmented views. One important factor for
providing such an accessible reality augmentation is the correct handling of
the occlusion of virtual objects by real scene elements. The usually large
volumetric datasets used in medicine are ill-suited for use as phantom models
for static occlusion handling. We present a simple and fast preprocessing
pipeline for medical volume datasets which extracts their visual hull volume.
The resulting, significantly simplified visual hull iso-surface is used for
real-time static occlusion handling in our AR system, which is based on
off-the-shelf medical equipment.

%M C.VRST.04.178
%T NOYO: 6DOF elastic rate control for virtual environments
%S Session 2C: techniques and applications (short papers)
%A Simon, Andreas
%A Doulis, Mario
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 178-181
%K elastic force input, input device, travel, virtual environment
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077571
%X It is an interesting challenge to design input devices that are easy to
learn and use and that allow a wide range of differentiated input. We have
developed a novel joystick-like handheld input device as a 6DOF elastic rate
controller for travel and rate-controlled object manipulation in virtual
environments. The NOYO combines a 6DOF elastic force sensor with a 3DOF
source-less isotonic orientation tracker. This combination allows consistent
mapping of input forces from local device coordinates to absolute world
coordinates, effectively making the NOYO a "SpaceMouse to go". The device is
designed to allow one-handed as well as two-handed operation, depending on the
task and the skill level of the user. A quantitative usability study shows the
handheld NOYO to be up to 21% faster, easier to learn, and significantly more
efficient than the SpaceMouse desktop device.

%M C.VRST.04.182
%T Tailor tools for interactive design of clothing in virtual environments
%S Session 2C: techniques and applications (short papers)
%A Keckeisen, Michael
%A Feurer, Matthias
%A Wacker, Markus
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 182-185
%K cloth modelling and simulation, interaction techniques, interactive design,
virtual prototyping
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077572
%X In this work, we present virtual tailor tools which allow the interactive
design and modification of clothing in a 3D Virtual Environment. In particular,
we propose algorithms and interaction techniques for sewing and cutting
garments during a physical cloth simulation, including the automatic
modification of the underlying planar cloth patterns.

%M C.VRST.04.186
%T Reality-augmented virtuality: modeling dynamic events from nature
%S Keynote speaker
%A Magnor, Marcus
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 186
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077574
%X Virtual Reality thrives on interactivity, realism, and increasingly also
animation. The virtual world is not a static place anymore: dynamic entities
mimicking natural phenomena are finding their way into computer games and
special effects. Typically, physics-based models or ad-hoc behavioral
descriptions are drawn on to emulate water waves, flames, smoke, cloth motion,
... For interactive VR applications, unfortunately, simulating complex physical
processes is often too time-consuming, while, on the other hand, simplified
model descriptions yield un-natural, artificial animation results.
   Alternatively, natural events may be acquired from the "real thing". Given a
handful of synchronized video recordings, this talk presents examples how
complex, time-varying natural phenomena may be modeled from reality to be
incorporated into time-critical 3D graphics applications. The reward are
photo-realistic rendering results and truly authentic animations.

%M C.VRST.04.187
%T Transpost: all-around display system for 3D solid image
%S Session 3A: devices and haptics
%A Otsuka, Rieko
%A Hoshino, Takeshi
%A Horry, Youichi
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 187-194
%K all-around display, stereo vision, telepresence
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077576
%X A novel method for an all-around display system that shows three-dimensional
stereo images without the need for special goggles has been developed. This
system simply needs a directional-reflection screen, mirrors, and a standard
projector. The basic concept behind this system is to make use of the
phenomenon called "afterimage" that occurs when screen is spinning. The key to
this approach is to make a directional reflection screen with a limited viewing
angle and project images onto it. The projected image is made up of 24 images
of an object, taken from 24 different angles. By reconstructing this image, a
three-dimensional object can be displayed on the screen. The display system can
present images of computer-graphics and photographs, full-length movies, and so
on.
   Our aim is to make a system for not only displaying images but also for
interacting with them. Several display examples demonstrated that the system
will be useful in applications such as guide displays in public places and
facilities.

%M C.VRST.04.195
%T Telerehabilitation: controlling haptic virtual environments through handheld
interfaces
%S Session 3A: devices and haptics
%A Gutiérrez, Mario
%A Lemoine, Patrick
%A Thalmann, Daniel
%A Vexo, Frédéric
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 195-200
%K handheld devices, haptic interfaces, kinesthetic therapy,
telerehabilitation, virtual environments
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077577
%X This paper presents a telerehabilitation system for kinesthetic therapy
(treatment of patients with arm motion coordination disorders). Patients can
receive therapy while being immersed in a virtual environment (VE) with haptic
feedback. Our system is based on a Haptic Workstation that provides
force-feedback on the upper limbs. One of our main contributions is the use of
a handheld device as the main interface for the therapist. The handheld allows
for monitoring, adapting and designing exercises in real-time (dynamic VE).
Visual contact with the patient is kept by means of a webcam.

%M C.VRST.04.201
%T Multi-resolution haptic interaction of hybrid virtual environments
%S Session 3A: devices and haptics
%A Chen, Hui
%A Sun, Hanqiu
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 201-208
%K haptics, multi-resolution representation, virtual environments
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077578
%X Our sense of touch is spatially focused and has a far lower bandwidth in
comparison with visual sense that has the largest bandwidth. While most haptic
studies utilize point interactions, resulting in a conflict between this low
information bandwidth and relative complexity of virtual scene. In this paper,
we investigate a novel multi-resolution force evaluation scheme of hybrid
virtual models in a unified haptic interaction framework. Force contact model
of tool-object interaction based on Hertz's contact theory is integrated in our
work. Physical properties with different object materials expressed by
Poisson's Ratio and Young's Modulus are involved to investigate most realistic
perception during multi-resolution haptic interaction. The hierarchical
impostor representation of surface and volumetric models are constructed, and
the optimal performance based on cost and benefit evaluation at run time is
employed to meet both the visual and hapic perceptual qualities. During this
multi-resolution haptic interaction, our scheme adaptively determines the
rendering mode using graphics and haptics impostors represented in the virtual
environments. Our experimental results have demonstrated the satisfactory
performance of proposed multi-resolution haptic interaction framework
applicable for hybrid virtual models.

%M C.VRST.04.209
%T Electrostatic tactile display with thin film slider and its application to
tactile tele-presentation systems
%S Session 3A: devices and haptics
%A Yamamoto, Akio
%A Nagasawa, Shuichi
%A Yamamoto, Hiroaki
%A Higuchitokyo, Toshiro
%B Proceedings of the 2004 ACM Symposium on Virtual Reality Software and
Technology
%D 2004
%P 209-216
%K cutaneous sensation, tactile display, tactile sensing, tele-presentation,
user interface, virtual reality
%* (c) Copyright 2004 ACM
%W http://doi.acm.org/10.1145/1077534.1077579
%X A new electrostatic tactile display is proposed to realize compact tactile
display devices that can be incorporated with virtual reality systems. The
tactile display of this study consists of a thin conductive film slider with
stator electrodes that excite electrostatic forces. Users of the device
experience tactile texture sensations by moving the slider with their fingers.
The display operates by applying two-phase cyclic voltage patterns to the
electrodes. This paper reports on the application of the new tactile display in
a tactile tele-presentation system. In the system, a PVDF tactile sensor and
DSP controller automatically generate voltage patterns to present surface
texture sensations through the tactile display. A sensor, in synchronization
with finger motion on the tactile display, scans a texture sample and outputs
information about the sample surface. The information is processed by a DSP and
fed back to the tactile display in real time. The tactile tele-presentation
system was evaluated in texture discrimination tests and demonstrated a 79%
correct answer ratio. A transparent electrostatic tactile display is also
reported in which the tactile display is combined with an LCD to realize a
visual-tactile integrated display system.