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VRST Tables of Contents: 979899000102030405060708091012131415

Proceedings of the 2005 ACM Symposium on Virtual Reality Software and Technology

Fullname:VRST'05 ACM Symposium on Virtual Reality Software and Technology
Editors:Gurminder Singh; Rynson Lau
Location:Monterey, California, USA
Dates:2005-Nov-07 to 2005-Nov-09
Publisher:ACM
Standard No:ISBN: 1-59593-098-1; Order Number: 609050; ACM DL: Table of Contents hcibib: VRST05
Papers:43
Pages:262
  1. Collaboration and cooperation -- I
  2. Human performance in virtual spaces
  3. Collaboration and cooperation -- II
  4. Interaction and design -- I
  5. Interaction and design -- II
  6. Virtual world content creation & management -- I
  7. Virtual world content creation & management -- II
  8. Spatial tracking, haptics & hardware
  9. Virtual people & scalable worlds
Art and technology in interface devices BIBAKFull-Text 1-7
  Hiroo Iwata
This paper presents work carried out for a project to develop interface devices for haptics that includes finger/hand manipulation, locomotion. It is well known that sense of touch is inevitable for understanding the real world. The last decade has seen significant advance in development of haptic interface. However, methods for implementation of haptic devices are still in try-and-error. Compared to visual and auditory displays, haptic display has not been used in everyday life. In order to overcome this limitation, we have been exhibiting the interface devices as art work. This paper introduces issues and solutions in haptic device through 18-years history of our research activities.
Keywords: embodied sensation, haptics, interface device

Collaboration and cooperation -- I

AMMP-Vis: a collaborative virtual environment for molecular modeling BIBAKFull-Text 8-15
  Jeffrey W. Chastine; Jeremy C. Brooks; Ying Zhu; G. Scott Owen; Robert W. Harrison; Irene T. Weber
Molecular modeling is an important research area, helping scientists develop new drugs against diseases such as AIDS and cancer. Prior studies have demonstrated that immersive virtual environments have unique advantages over desktop systems in visualizing molecular models. However, exploration and interaction in existing molecular modeling virtual environments is often limited to a single user, lacking strong support for collaboration. In addition, scientists are often reluctant to adopt these systems because of their lack of availability and high cost. We propose an affordable immersive system that allows biologists and chemists to manipulate molecular models via natural gestures, receive and visualize real-time feedback from a molecular dynamics simulator, allow the sharing of customized views, and provide support for both local and remote collaborative research.
Keywords: augmented reality, collaboration, interaction techniques, molecular modeling, shaders, virtual environments
A 2D-3D integrated environment for cooperative work BIBAKFull-Text 16-22
  Kousuke Nakashima; Takashi Machida; Kiyoshi Kiyokawa; Haruo Takemura
This paper proposes a novel tabletop display system for natural communication and flexible information sharing. The proposed system is specifically designed for integration of 2D and 3D user interfaces, using a multi-user stereoscopic display, IllusionHole. The proposed system takes awareness into consideration and provides both 2D and 3D information and user interfaces. On the display, a number of standard Windows desktop environments are provided as personal workspaces, as well as a shared workspace with a dedicated graphical user interface. In personal workspaces, users can simultaneously access existing applications and data, and exchange information between personal and shared workspaces. In this way, the proposed system can seamlessly integrate personal, shared, 2D and 3D workspaces with conventional user interfaces and effectively support communication and information sharing. To demonstrate capabilities of the proposed display system, a modeling application has been implemented. A preliminary experiment confirmed the effectiveness of the system.
Keywords: 2D - 3D integrated user interface, IllusionHole, VNC
First-person experience and usability of co-located interaction in a projection-based virtual environment BIBAKFull-Text 23-30
  Andreas Simon
Large screen projection-based display systems are very often not used by a single user alone, but shared by a small group of people. We have developed an interaction paradigm allowing multiple users to share a virtual environment in a conventional single-view stereoscopic projection-based display system, with each of the users handling the same interface and having a full first-person experience of the environment.
   Multi-viewpoint images allow the use of spatial interaction techniques for multiple users in a conventional projection-based display. We evaluate the effectiveness of multi-viewpoint images for ray selection and direct object manipulation in a qualitative usability study and show that interaction with multi-viewpoint images is comparable to fully head-tracked (single-user) interaction. Based on ray casting and direct object manipulation, using tracked PDA's as common interaction device, we develop a technique for co-located multi-user interaction in conventional projection-based virtual environments. Evaluation of the VRGEO Demonstrator, an application for the review of complex 3D geo-seismic data sets in the oil-and-gas industry, shows that this paradigm allows multiple users to each have a full first-person experience of a complex, interactive virtual environment.
Keywords: PDA interaction, co-located collaboration, projection-based virtual environment, single display groupware

Human performance in virtual spaces

Human performance in space telerobotic manipulation BIBAKFull-Text 31-37
  Philip Lamb; Dean Owen
This paper considers the utility of VR in the design of the interface to a space-based telerobotic manipulator. An experiment was conducted to evaluate the potential for improved operator performance in a telemanipulation task when the operator's control interface was varied between egocentric and exocentric frames of reference (FOR). Participants performed three tasks of increasing difficulty using a VR-based simulation of the Space Shuttle Remote Manipulation System (SRMS) under four different control interface conditions, which varied in respect of two factors, virtual viewpoint FOR (fixed versus attached to arm) and hand controller FOR (end-effector-referenced versus world-referenced.) Results indicated a high degree of interaction between spatial properties of the task and the optimal interface condition. Across all tasks, the conditions under end-effector-referenced control were associated with higher performance, as measured by rate of task completion. The mobile viewpoint conditions were generally associated with lower performance on task completion rate but improved performance with respect to number of collisions between the arm and objects in the environment. We conclude with discussion of implications for telemanipulation applications, and an approach to varying the dimension of viewpoint egocentricity in order to improve performance under the mobile viewpoint.
Keywords: SRMS, frame of reference, telerobotics, user studies
Mixed-dimension interaction in virtual environments BIBAKFull-Text 38-45
  Rudolph P. Darken; Richard Durost
In this paper, we present a study to show that matching the dimensionality of interaction techniques with the dimensional demands of the task results in an interface that facilitates superior performance on interaction tasks without sacrificing performance on 2D tasks in favor of 3D tasks and vice versa. We describe the concept of dimensional congruence and how to identify the dimensional characteristics of a task so that appropriate interaction techniques can be applied. We constructed a prototypical application in a Virtual Environment Enclosure (VEE) using a hand-held device to show how this might be done in this type of apparatus. We then describe a study that evaluates both 2D and 3D tasks as performed using typical 2D and 3D interaction techniques. Results show that an appropriate mix of 2D and 3D interaction techniques is preferred over exclusive use of one or the other. The challenge lies not in selecting independent interaction techniques for specific tasks, but rather in constructing an overall interface that mixes 2D and 3D interactions appropriately.
Keywords: human factors, interaction technique, virtual environments
Effects of information layout, screen size, and field of view on user performance in information-rich virtual environments BIBAKFull-Text 46-55
  Nicholas F. Polys; Seonho Kim; Doug A. Bowman
This paper describes our recent experimental evaluation of Information-Rich Virtual Environment (IRVE) interfaces. To explore the depth cue/visibility tradeoff between annotation schemes, we design and evaluate two information layout techniques to support search and comparison tasks. The techniques provide different depth and association cues between objects and their labels: labels were displayed either in the virtual world relative to their referent (Object Space) or on an image plane workspace (Viewport Space). The Software Field of View (SFOV) was controlled to 60 or 100 degrees of vertical angle and two groups were tested: those running on a single monitor and those on a tiled nine-panel display. Users were timed, tracked for correctness, and gave ratings for both difficulty and satisfaction on each task. Significant advantages were found for the Viewport interface, and for high SFOV. The interactions between these variables suggest special design considerations to effectively support search and comparison performance across monitor configurations and projection distortions.
Keywords: 3D interaction, information-rich virtual environments, usability testing and evaluation, visual design
A novel framework for athlete training based on interactive motion editing and silhouette analysis BIBAKFull-Text 56-58
  Shihong Xia; Xianjie Qiu; Zhaoqi Wang
There are mainly two Hi-Tech methods for athlete training. One method is based on virtual reality, where the athlete can learn and improve performance mainly through using virtual equipments to interact with the virtual environment. Another method is based on video analysis, where improvements can be made by comparing the videos of the trainees with those of excellent trainers. In this paper, we present a novel framework for athlete training, which can circumvent difficulties the current methods faced in practical applications. For retargeting the example motion to personalized virtual athlete, the coach interactively sets motion constraints with his experience based on motion warping and motion verification techniques. The display of the simulated motion is adjusted semi-automatically to create the reference virtual video with the same viewpoint as the real one. The moment invariants of both virtual and real athlete's silhouette are computed, and motion analysis result is presented subsequently. This method is more suitable for gymnastic athlete training because of without virtual equipment and more instructive having the same viewpoint in video analysis. Finally, an application of the proposed techniques to trampoline training is implemented.
Keywords: moment invariants, motion editing, motion training
An integrated system: virtual reality, haptics and modern sensing technique (VHS) for post-stroke rehabilitation BIBAKFull-Text 59-62
  Shih-Ching Yeh; Albert Rizzo; Weirong Zhu; Jill Stewart; Margaret McLaughlin; Isaac Cohen; Younbo Jung; Wei Peng
In this paper, we introduce an interdisciplinary project, involving researchers from the fields of Physical Therapy, Computer Science, Psychology, Communication and Cell Neurobiology, to develop an integrated virtual reality, haptics and modern sensing technique system for post-stroke rehabilitation. The methodology to develop the system includes identification of movement pattern, development of simulated task and diagnostics. Each part of the methodology can be achieved through several sub-steps that are described in detail in this paper. The system is designed from Physical Therapy perspective that can address the motor rehabilitation needs of stroke patients. The system is implemented through stereoscopic displays, force feedback devices and modern sensing techniques that have game-like features and can capture accurate data for further analysis. Diagnostics and evaluation can be made through an Artificial Intelligence based model using collected data and clinical tests have been conducted.
Keywords: haptics, physical therapy, stroke rehabilitation, virtual reality, visual sensing

Collaboration and cooperation -- II

Telepresence support for synchronous distance BIBAKFull-Text 63-67
  Juliana Restrepo; Helmuth Trefftz
This paper describes a telepresence application that combines bi-directional video, audio and a shared virtual environment as means to support synchronous distance education sessions.
   In order to validate the effectiveness of the tool, it was used in several courses at our University. Students were divided into an experimental group -- using the tool in a simulated distance learning environment -- and a control group -- receiving traditional face-to-face lectures --. The results show that the use of the telepresence application, hand in hand with an appropriate pedagogical framework, lead the students in the distance education sessions to reach at least the same levels of understanding, and sometimes even better, than those attained by students in the face-to-face sessions.
   We are offering the telepresence application to other education institutions in our country, with the hope that it will allow students in regions isolated by the war or by the lack of infrastructure to have access to better education, both at school and university levels.
Keywords: collaborative virtual reality, computer graphics, networked virtual environments
Myriad: scalable VR via peer-to-peer connectivity, PC clustering, and transient inconsistency BIBAKFull-Text 68-77
  Benjamin Schaeffer; Peter Brinkmann; George Francis; Camille Goudeseune; Jim Crowell; Hank Kaczmarski
Distributed scene graphs are important in virtual reality, both in collaborative virtual environments and in cluster rendering. In Myriad, individual scene graphs form a peer-to-peer network whose connections filter scene graph updates and create flexible relationships between scene graph nodes in the various peers. Modern scalable visualization systems often feature high intracluster throughput, but collaborative virtual environments (VEs) over a WAN share data at much lower rates, complicating the use of one scene graph system across the whole application. To avoid these difficulties, Myriad uses fine-grained sharing, whereby sharing properties of individual scene graph nodes can be dynamically changed from C++ and Python, and transient inconsistency, which relaxes resource requirements in collaborative VEs. A test application, WorldWideCrowd, implements these methods to demonstrate collaborative prototyping of a 300-avatar crowd animation viewed on two PC-cluster displays and edited on low-powered laptops, desktops, and even over a WAN.
Keywords: PC cluster, peer-to-peer, virtual environments
Quantifying the benefits of immersion for collaboration in virtual environments BIBAKFull-Text 78-81
  Michael Narayan; Leo Waugh; Xiaoyu Zhang; Pradyut Bafna; Doug Bowman
Collaborative Virtual Environments allow multiple users to interact collaboratively while taking advantage of the perceptual richness that Virtual Environments (VEs) provide. In this paper, we demonstrate empirically that increasing the level of immersion in a VE can have a beneficial effect on the usability of that environment in a collaborative context. We present the results of a study in which we varied two immersive factors, stereo and head tracking, within the context of a two person collaborative task. Our results indicate that stereo can have a positive effect on task performance; that different levels of immersion have effects that vary with gender; and that varying the level of immersion has a pronounced effect on communication between users. These results show that the level of immersion can play an important role in determining user performance on some collaborative tasks.
Keywords: collaborative virtual environments, head tracking, immersion, stereo
Scalable interest management for multidimensional routing space BIBAKFull-Text 82-85
  Elvis S. Liu; Milo K. Yip; Gino Yu
Interest management is essential for scalable collaborative virtual environments (CVEs) which sought to reduce bandwidth consumption on the network. Most of the interest management systems such as Data Distribution Management (DDM) service of the High Level Architecture (HLA) concentrate on providing precise message filtering mechanisms. However, in doing so a second problem is introduced: the CPU cycle overheads of filtering process. If the cost in terms of computational resources of interest management itself is too high, it would be unsuitable for real time applications such as multiplayer online games (MOGs) for which runtime performance is important. In this paper we present a scalable interest management algorithm which is suitable for HLA DDM. Our approach employs the collision detection method of I-COLLIDE for fast interest matching. Furthermore, the algorithm has been implemented in our commercialized MOG middleware -- Lucid Platform. Experimental evidence demonstrates that it works well in practice.
Keywords: collaborative virtual environments, collision detection, computer games, data distribution management, high level architecture, interest management

Interaction and design -- I

Towards keyboard independent touch typing in VR BIBAKFull-Text 86-95
  Falko Kuester; Michelle Chen; Mark E. Phair; Carsten Mehring
A new hand- or finger-mounted data input device, called KITTY, is presented. KITTY is designed for keyboard independent touch typing and supports traditional touch-typing skills as a method for alphanumeric data input. This glove-type device provides an ultra-portable solution for "quiet" data input into portable computer systems and full freedom of movement in mobile VR and AR environments. The KITTY design follows the concept of the column and row layout found on traditional keyboards, allowing users to draw from existing touch typing skills, easing the required training time.
Keywords: glove input, interaction techniques, keyboard independent touch-typing, wearable devices for augmented reality
A layout framework for 3D user interfaces BIBAKFull-Text 96-105
  Wai Leng Lee; Mark Green
Two of the main problems facing the developers of 3D user interface are the wide range of device configurations that must be supported and the lack of software tools for constructing 3D user interfaces. The Grappl project aims to solve these problems by producing user interfaces that adapt to the device configurations that they encounter at runtime. Since the user interface is constructed at runtime one of the problems confronted by Grappl is laying out the different user interface components and possibly some of the application objects. This paper presents a framework for automating the layout of 3D user interfaces, including the types of information provided by the user interface designer, the high level architecture of the layout system and the algorithms used for empty space management.
Keywords: 3D user interface, layout techniques
A practical system for laser pointer interaction on large displays BIBAKFull-Text 106-109
  Benjamin A. Ahlborn; David Thompson; Oliver Kreylos; Bernd Hamann; Oliver G. Staadt
Much work has been done on the development of laser pointers as interaction devices. Typically a camera captures images of a display surface and extracts a laser pointer dot location. This location is processed and used as a cursor position. While the current literature well explains such a system, we feel that some important practical concerns have gone unaddressed. We discuss the design of such a tracking system, focusing on key practical implementation details. In particular we present a robust and efficient dot detection algorithm that allows us to use our system under a variety lighting conditions, and allows us to reduce the amount of image parsing required to find a laser position by an order of magnitude.
Keywords: interaction, laser pointer, tiled displays
A 6-DOF user interface for grasping in VR-based computer aided styling and design BIBAKFull-Text 110-112
  Frank-Lothar Krause; Johann Habakuk Israel; Jens Neumann; Boris Beckmann-Dobrev
We describe a 6-DoF (degrees of freedom) force-feedback enabled user interface that supports grasp interaction in mixed or virtual reality environments. The graspable part of the device is interchangeable. It can hold physical grips, tubes, work pieces and tools which provide passive haptic feedback, up to tangible user interfaces. The device is prepared to be integrated into holobench environments for unifying input and output space so that users can apply their sensorimotor skills for efficient interaction and task solving. Current applications are in the field of VR-based Computer Aided Styling and Design.
Keywords: direct object manipulation, haptic interaction, kinesthetic augmentation, multimodal interfaces, passive haptic devices, sensorimotor coordination, tangible user interfaces, tool based interaction, virtual reality
A swarm algorithm for wayfinding in dynamic virtual worlds BIBAKFull-Text 113-116
  Ji Soo Yoon; Mary Lou Maher
Wayfinding is a cognitive element of navigation that allows people to plan and form strategies prior to executing them. Wayfinding in large scale virtual environments is a complex task and even more so in dynamic virtual worlds. In these dynamic worlds everything, including the objects, the paths, and the landmarks, may be created, deleted, and moved at will. We propose a wayfinding tool using swarm creatures to aid users in such dynamic environments. The tool produces dynamic trails leading to desired destinations and generates teleport/warp gates. These are created as a consequence of swarm creatures exploring dynamic worlds. In this paper, we describe the swarm algorithms developed to create such a tool to generate wayfinding aids in dynamic virtual worlds.
Keywords: navigation, navigation/wayfinding aids, swarm intelligence, virtual worlds, wayfinding

Interaction and design -- II

Cognitive comparison of 3D interaction in front of large vs. small displays BIBAKFull-Text 117-123
  F. Tyndiuk; G. Thomas; V. Lespinet-Najib; C. Schlick
This paper presents some experimental results on the comparison of users performance for different kinds of 3D interaction tasks (travel, manipulation), when using either a standard desktop display or a large immersive display. The main results of our experimentation are the following: first, not all users benefit similarly from the use of large displays, and second, the gains of performance strongly depend on the nature of the interaction task. To explain these results, we borrow some tools from cognitive science in order to identify one cognitive factor (visual attention) that is involved in the difference of performance that can be observed.
Keywords: cognitive aids, display size, interaction, virtual reality, visual attention
A low cost and accurate guidance system for laparoscopic surgery: validation on an abdominal phantom BIBAKFull-Text 124-133
  S. A. Nicolau; L. Goffin; L. Soler
In this paper we present a guiding system for laparoscopic surgery which tracks in real time the laparoscopic tools and registers at 10 Hz a preoperative CT/MRI model of the patient. To help surgeons, this system provides simultaneously three kinds of supplementary information. It displays the relative positions of the laparoscopic tools and the 3D patient model. It provides two external views of the patient on which his 3D model and tool positions are superimposed. Finally, it displays an endoscopic view augmented with the 3D patient model. Contrary to most systems for laparoscopic surgery, this one is low cost (one PC, two cameras and a printer are necessary) and we have rigorously validated its tracking accuracy in simulated clinical conditions (tracking accuracy of an instrument tip close to 1.5 mm, and endoscopic overlay error under 1.0 mm). Besides, our system accuracy is comparable with commercial system's ones. Eventually, experiments on an abdominal phantom with surgeons demonstrate its usefulness. We plan to realize our first experiments on patients in a few months.
Keywords: accuracy evaluation, computer-aided surgery, endoscopic tool calibration and tracking, registration
BalloonProbe: reducing occlusion in 3D using interactive space distortion BIBAKFull-Text 134-137
  Niklas Elmqvist
Using a 3D virtual environment for information visualization is a promising approach, but can in many cases be plagued by a phenomenon of literally not being able to see the forest for the trees. Some parts of the 3D visualization will inevitably occlude other parts, leading both to loss of efficiency and, more seriously, correctness; users may have to change their viewpoint in a non-trivial way to be able to access hidden objects, and, worse, they may not even discover some of the objects in the visualization due to this inter-object occlusion. In this paper, we present a space distortion interaction technique called the BalloonProbe which, on the user's command, inflates a spherical force field that repels objects around the 3D cursor to the surface of the sphere, separating occluding objects from each other. Inflating and deflating the sphere is performed through smooth animation, ghosted traces showing the displacement of each repelled object. Our prototype implementation uses a 3D cursor for positioning as well as for inflating and deflating the force field "balloon". Informal testing suggests that the BalloonProbe is a powerful way of giving users interactive control over occlusion in 3D visualizations.
Keywords: 3D space distortion, interaction technique, occlusion reduction
Projective slice for a dynamic steering task BIBAKFull-Text 138-141
  Pierre Salom; Javier Becerra; Marc Donias; Rémi Megret
Volume visualization using 2-D slices is a technique exploited in several scientific fields such as medicine, geology or any other industrial application using 3D data. The expert has the possibility to explore the data by displaying a set of slices extracted from the volume. The objective is to detect some specific three-dimensional structure and point it in 2-D, directly on slices with a device. This type of interaction realized during the animation of slices is named dynamic pointing. To formalize this task we define in this article a new paradigm: the dynamic steering task (DST). We first relate it with the other tasks studied in Human-Computer Interaction. This study helps us to better understand the reason of the difficulty of this task and why users produce so many positioning errors. We formulate the hypothesis that the errors generated in a DST are coming from the impossibility for the experts to anticipate the structural variations of the structures to be pointed. In order to solve this problem we propose a new technique of visualization, which facilitates anticipation, called the projective slice. The effectiveness of this tool and the veracity of our assertions are determined experimentally.
Keywords: dynamic pointing, dynamic steering task, preview, projective slice
Graphics: from a 100x data expansion to a 100x compression function BIBAFull-Text 142
  Eng Lim Goh
In the mid 1980s, a typical large data visualization, involved the input of geometry in the order of 10,000 triangles, for rendering into about a million display pixels. However, today, we see input data sets growing to a billion triangles, while the generated display has only grown to about 10 million pixels. Consequently, large data visualization have, over the years, changed from a data expansion, to a data compression function.
   This four orders of magnitude change has evoked renewed interests in ray tracing rendering techniques, of which its performance can be made more input geometry-quantity insensitive. This is as opposed to scanline rendering techniques, such as OpenGL, that can be made more output pixel-quantity insensitive.
   For those staying with scanline techniques, the enormous growth in geometry count has made it necessary for the development of scalable parallel rendering. This is where tens of Graphics Processing Units (GPUs) are coordinated to render one large geometric data set. After the pixels are produced by each of these GPUs, ways of compositing their individual output into a single display, with feedback loops for dynamic load balancing, may be necessary.
   As the crossover "from expansion to compression" continues, it will become increasingly practical, in certain remote visualization sessions, to invent ways to transmit only the generated pixels; instead of the traditional method of transmitting the entire geometric data set for pixel generation at the remote user's station. Add to this the advances in display, lighting and input technologies for mobile handheld devices, interesting new applications may evolve for the scientific, engineering and creative users.

Virtual world content creation & management -- I

Rapid part-based 3D modeling BIBAKFull-Text 143-146
  Ismail Oner Sebe; Suya You; Ulrich Neumann
An intuitive and easy-to-use 3D modeling system has become more crucial with the rapid growth of computer graphics in our daily lives. Image-based modeling (IBM) has been a popular alternative to pure 3D modelers (e.g. 3D Studio Max, Maya) since its introduction in the late 1990s. However, IBM techniques are inherently very slow and rarely user friendly. Most IBM techniques require either very extensive manual input and/or multiple images. In this paper, we present an IBM technique that gives high level of detail with 1-2 minutes of manipulation from a novice user using only single, un-calibrated image. Our system modifies a generic part-based model of the object under investigation. User inputs are entered via a simple interface and converted into modifications to the whole 3D model. We demonstrate the effectiveness of our modeler by modeling several vehicles, such as SUVs, sedan/hatchback/coupe cars, minivans, trucks and more.
Keywords: image based modeling and rendering, part-based modeling, rapid 3D modeling
Rapid scene modelling, registration and specification for mixed reality systems BIBAKFull-Text 147-150
  Russell Freeman; Anthony Steed; Bin Zhou
Many mixed-reality systems require real-time composition of virtual objects with real video. Such composition requires some description of the virtual and real scene geometries and calibration information for the real camera. Once these descriptions are available, they can be used to perform many types of visual simulation including virtual object placement, occlusion culling, texture extraction, collision detection and reverse and re-illumination methods.
   In this paper we present a demonstration where we rapidly register prefabricated virtual models to a videoed scene. Using this registration information we were able to augment animated virtual avatars to create a novel mixed reality system. Rather than build a single monolithic system, we briefly introduce our lightweight modelling tool, the Mixed-Reality Toolkit (MRT) which enables rapid reconfiguration of scene objects without performing a full reconstruction. We also generalise to outline some initial requirements for a Mixed Reality Modelling Language (MRML).
Keywords: camera calibration, mixed reality, modelling from images
Modeling landscapes with ridges and rivers BIBAKFull-Text 151-154
  Farès Belhadj; Pierre Audibert
Generating realistic models of landscapes with drainage network is a major field in computer graphics. In this paper, we present a fractal based method which generates natural terrains using ridges and rivers information. As opposed to methods that compute water erosion for a given terrain model, our terrain mesh is generated constrained by a predefined set of ridge lines and rivers network. A new extension of the midpoint displacement model is used in this context. The resulting landscapes meshes leads to realistic rendering and our method seems to be very promising.
Keywords: fractals, midpoint displacement, terrain erosion, terrain models
Artistic reality: fast brush stroke stylization for augmented reality BIBAKFull-Text 155-158
  Jan Fischer; Dirk Bartz; A Wolfgang Straβer
The goal of augmented reality is to provide the user with a view of the surroundings enriched by virtual objects. Practically all augmented reality systems rely on standard real-time rendering methods for displaying graphical objects. Although such conventional computer graphics algorithms are fast, they often fail to produce sufficiently realistic renderings. Therefore, virtual models can easily be distinguished from the real environment. We have recently proposed a novel approach for generating augmented reality images [4]. Our method is based on the idea of applying stylization techniques for adapting the visual realism of both the camera image and the virtual graphical objects. Since both the camera image and the virtual objects are stylized in a corresponding way, they appear very similar. Here, we present a new method for the stylization of augmented reality images. This approach generates a painterly brush stroke rendering. The resulting stylized augmented reality video frames look similar to paintings created in the pointillism style. We describe the implementation of the camera image filter and the non-photorealistic renderer for virtual objects. These components have been newly designed or adapted for this purpose. They are fast enough for generating augmented reality images in near real-time (more than 14 frames per second).
Keywords: augmented reality, brush stroke style, non-photorealistic rendering, real-time stylization
DiReC: distributing the render cache to PC-clusters for interactive environments BIBAKFull-Text 159-162
  Nils Beck; André Hinkenjann
The Render Cache [1,2] allows the interactive display of very large scenes, rendered with complex global illumination models, by decoupling camera movement from the costly scene sampling process. In this paper, the distributed execution of the individual components of the Render Cache on a PC cluster is shown to be a viable alternative to the shared memory implementation.
   As the processing power of an entire node can be dedicated to a single component, more advanced algorithms may be examined. Modular functional units also lead to increased flexibility, useful in research as well as industrial applications.
   We introduce a new strategy for view-driven scene sampling, as well as support for multiple camera viewpoints generated from the same cache. Stereo display and a CAVE multi-camera setup have been implemented.
   The use of the highly portable and inter-operable CORBA networking API simplifies the integration of most existing pixel-based renderers. So far, three renderers (C++ and Java) have been adapted to function within our framework.
Keywords: clusters, render cache
Computing inverse kinematics with linear programming BIBAKFull-Text 163-166
  Edmond S. L. Ho; Taku Komura; Rynson W. H. Lau
Inverse Kinematics (IK) is a popular technique for synthesizing motions of virtual characters. In this paper, we propose a Linear Programming based IK solver (LPIK) for interactive control of arbitrary multibody structures. There are several advantages of using LPIK. First, inequality constraints can be handled, and therefore the ranges of the DOFs and collisions of the body with other obstacles can be handled easily. Second, the performance of LPIK is comparable or sometimes better than the IK method based on Lagrange multipliers, which is known as the best IK solver today. The computation time by LPIK increases only linearly proportional to the number of constraints or DOFs. Hence, LPIK is a suitable approach for controlling articulated systems with large DOFs and constraints for real-time applications.
Keywords: inverse kinematics, linear programming, real-time motion synthesis

Virtual world content creation & management -- II

Dynamic creation of interactive mixed reality presentations BIBAKFull-Text 167-176
  Krzysztof Walczak; Rafal Wojciechowski
In this paper, we describe a method of dynamic creation of interactive presentations for Mixed Reality environments. The presentations are created automatically for collections of multimedia objects arbitrarily arranged in virtual presentation spaces stored in a database. Users can navigate between the spaces using Web and 3D multimedia contents. The objects in each space are presented through a presentation template, which determines both the visualization and the interaction aspects of the presentation. The possible user interactions are described using a novel language called MR-ISL. The presentation templates are coded in X?VRML, a high-level modeling language. The method can be used in various application domains. Examples discussed in the paper relate to presentation of cultural heritage and educational resources.
Keywords: VRML, X?VRML, interaction scenarios, mixed reality, virtual reality
Integrated levels of detail BIBAKFull-Text 177-183
  Georgios Stylianou; Yiorgos Chrysanthou
We introduce a new mesh representation for arbitrary surfaces that integrates different levels of detail into the final representation. It is produced after remeshing an existing model and omits storing connectivity information. Switching between resolutions can be instantly accomplished without extra computation. This representation is generated by chartifying initial the mesh, parametrizing and re-meshing each chart using a regular grid of control points in a multilevel approach. Finally, the model becomes watertight by hierarchically stitching each chart's boundary points and normals.
Keywords: multiresolution, remeshing, surface parametrization
Generating enhanced natural environments and terrain for interactive combat simulations (GENETICS) BIBAKFull-Text 184-191
  William D. Wells
Virtual battlefields devoid of vegetation deprive soldiers of valuable training in the critical aspects of terrain tactics and terrain-based situational awareness. Creating believable landscapes by hand is notoriously expensive, requiring both proprietary tools and trained artists, which hampers rapid scenario generation and limits reuse. Our approach constructs large-scale natural environments at run-time using a procedural image-based algorithm without the need for artists or proprietary tools.
   This paper discusses the current state of the open source project GENETICS (Generating Enhanced Natural Environments and Terrain for Interactive Combat Simulations) and how simulationists can use GENETICS to quickly and cheaply build large-scale natural environments to improve training effectiveness. It will also briefly touch upon level-of-detail techniques and ecotype modeling.
Keywords: automated vegetation placement, landscape visualization, run-time terrain database generation

Spatial tracking, haptics & hardware

Real time tracking of high speed movements in the context of a table tennis application BIBAKFull-Text 192-200
  Stephan Rusdorf; Guido Brunnett
In this paper we summarize the experiences we made with the implementation of a table tennis application. After describing the hardware necessities of our system we give insight into different aspects of the simulation. These include collision detection, physical simulation and some aspects of the design of the virtual opponent.
   Since table tennis is one of the fastest sports the synchronization of the player's movements and the visual output on the projection wall is the most challenging problem to solve. Therefore we analysed the latencies of all subcomponents of our system and designed a prediction method that allows high speed interaction with our application.
Keywords: collision detection, latency, prediction, table tennis, tracking, virtual reality
A general method for comparing the expected performance of tracking and motion capture systems BIBAKFull-Text 201-210
  B. Danette Allen; Greg Welch
We introduce a general method for evaluating and comparing the expected performance of sensing systems for interactive computer graphics. Example applications include head tracking systems for virtual environments, motion capture systems for movies, and even multi-camera 3D vision systems for image-based visual hulls.
   Our approach is to estimate the asymptotic position and/or orientation uncertainty at many points throughout the desired working volume, and to visualize the results graphically. This global performance estimation can provide both a quantitative assessment of the expected performance, and intuition about the type and arrangement of sources and sensors, in the context of the desired working volume and expected scene dynamics.
Keywords: computer vision, covariance analysis, information visualization, motion capture, sensor fusion, tracking, virtual environments
Object deformation and force feedback for virtual chopsticks BIBAKFull-Text 211-219
  Yoshifumi Kitamura; Ken'ichi Douko; Makoto Kitayama; Fumio Kishino
This paper proposes a virtual chopsticks system using force feedback and object deformation with FEM (finite element model). The force feedback model is established by using a leverage based on the correct chopsticks handling manner, and the force is applied to the index and middle finger. The object deformation is obtained in real-time by calculating inverse stiffness matrix beforehand. We performed experiments to compare the hardness of virtual objects. As a result, we found that a recognition rate of almost 100% can be achieved between virtual objects where the logarithmic difference in hardness is 0.4 or more, while lower recognition rates are obtained when the difference in hardness is smaller than this.
Keywords: FEM, deformation, force feedback, object manipulation, virtual chopsticks, virtual environment
Search and transitioning for motion captured sequences BIBAKFull-Text 220-223
  Suddha Basu; Shrinath Shanbhag; Sharat Chandran
Animators today have started using motion captured (mocap) sequences to drive characters. Mocap allows rapid acquisition of highly realistic animation data. Consequently animators have at their disposal an enormous amount of mocap sequences which ironically has created a new retrieval problem. Thus, while working with mocap databases, an animator often needs to work with a subset of "useful" clips. Once the animator selects a candidate working set of motion clips, she then needs to identify appropriate transition points amongst these clips for maximal reuse.
   In this paper, we describe methods for querying mocap databases and identifying transitions for a given set of clips. We preprocess clips (and clip subsequences), and precompute frame locations to allow interactive stitching. In contrast with existing methods that view each individual clips as nodes, for optimal reuse, we reduce the granularity.
Keywords: motion capture, motion synthesis, query by example, transition
Laser scanning for the interactive walk-through fogScreen BIBAKFull-Text 224-226
  Ismo Rakkolainen; Karri Palovuori
FogScreen is a free space 2D projection screen, which enables to touch and walk through an immaterial image. FogScreen consists of flowing air with a little visible humidity in the center of flow, and enables high-quality projected images in thin air, and many new applications.
   The FogScreen can be made interactive. Robust tracking of the user's pointing is a key element of the interactive system. In this short paper we present robust tracking employing laser scanning.
Keywords: fogScreen, touch screen, tracking, walk-through screen
POLAR: portable, optical see-through, low-cost augmented reality BIBAKFull-Text 227-230
  Alex Olwal; Tobias Höllerer
We describe POLAR, a portable, optical see-through, low-cost augmented reality system, which allows a user to see annotated views of small to medium-sized physical objects in an unencumbered way. No display or tracking equipment needs to be worn. We describe the system design, including a hybrid IR/vision head-tracking solution, and present examples of simple augmented scenes. POLAR's compactness could allow it to be used as a lightweight and portable PC peripheral for providing mobile users with on-demand AR access in field work.
Keywords: augmented reality, compact, low-cost, optical see-through, portable, projection
Experiences in driving a cave with IBM scalable graphics engine-3 (SGE-3) prototypes BIBAKFull-Text 231-234
  A Prabhat; Samuel G. Fulcomer
The IBM Scalable Graphics Engine-3 (SGE-3) prototype is a network attached framebuffer. In its application at Brown, it is a pixel compositor for distributed rendering and a video source for frame-sequential stereo display in a four-wall CAVE-like display, a TAN VR-Cube. The configuration uses 4 SGE-3 prototype units (one per display wall) and 48 rendering nodes (12 per display wall; 6 per stereo field). With favorable rendering distribution, achieved performance per 12-node wall has been up to five times that of a single graphics card. This report provides details of the cluster systems architecture and the performance characteristics of the SGE-3 and sample test applications.
Keywords: cave, compositors, distributed graphics, virtual reality

Virtual people & scalable worlds

Efficient compression and delivery of stored motion data for avatar animation in resource constrained devices BIBAKFull-Text 235-243
  Siddhartha Chattopadhyay; Suchendra M. Bhandarkar; Kang Li
Animation of Virtual Humans (avatars) is done typically using motion data files that are stored on a client or streaming motion data from a server. Several modern applications require avatar animation in mobile networked virtual environments comprising of power constrained clients such as PDAs, Pocket-PCs and notebook PCs operating in battery mode. These applications call for efficient compression of the motion animation data in order to conserve network bandwidth, and save power at the client side during data reception and motion data reconstruction from the compressed file. In this paper, we have proposed and implemented a novel file format, termed the Quantized Motion Data (QMD) format, which enables significant, though lossy, compression of the motion data. The motion distortion resulting from the reconstructed motion from the QMD file is minimized by intelligent use of the hierarchical structure of the skeletal avatar model. The compression gained by using the QMD files for the motion data is more than twice achieved via standard MPEG-4 compression using a pipeline comprising of quantization, predictive encoding and arithmetic coding. In addition, considerably fewer CPU cycles are needed to reconstruct the motion data from the QMD files compared to motion data compressed using the MPEG-4 standard.
Keywords: avatar animation, distributed virtual reality, human motion
Simulating virtual crowds in emergency situations BIBAKFull-Text 244-252
  Adriana Braun; Bardo E. J. Bodmann; Soraia R. Musse
This paper presents a novel approach to simulate virtual human crowds in emergency situations. Our model is based on two previous works, on a physical model proposed by Helbing, where individuals are represented by a particle system affected by "social forces" that impels them to go to a point-objective, while avoiding collisions with obstacles and other agents. As a new property, the virtual agents are endowed with different attributes and individualities as proposed by Braun et al. The main contributions of this paper are the treatment of complex environments and their implications on agents' movement, the management of alarms distributed in space, the virtual agents endowed with perception of emergency events and their consequent reaction as well as changes in their individualities. The prototype reads a XML file where different scenarios can be simulated, such as the characteristics of population, the virtual scene description, the alarm configuration and the properties of hazardous events. As output, the prototype generates information in order to measure the impact of parameters on saved, injured and dead agents. In addition, some results and validation are discussed.
Keywords: behavioral animation, crowd simulation, physically based animation
Motion normalization: the preprocess of motion data BIBAKFull-Text 253-256
  Yan Gao; Lizhuang Ma; Zhihua Chen; Xiaomao Wu
In this paper, we present an online algorithm to normalize all motion data in database with a common skeleton length. Our algorithm is very simple and efficient. The input motion stream is processed sequentially while the computation for a single frame at each step requires only the results from the previous step over a neighborhood of nearby backward frames. In contrast to previous motion retargeting approaches, we simplify the constraint condition of retargeting problem, which leads to the simpler solutions. Moreover, we improve Shin et al.'s algorithm [10], which is adopted by a widely used Kovar's footskate cleanup algorithm [6] through adding one case missed by it.
Keywords: motion capture, motion normalization, motion retargeting
Automatic generation of personalized human avatars from multi-view video BIBAKFull-Text 257-260
  Naveed Ahmed; Edilson de Aguiar; Christian Theobalt; Marcus Magnor; Hans-Peter Seidel
In multi-user virtual environments real-world people interact via digital avatars. In order to make the step from the real world onto the virtual stage convincing the digital equivalent of the user has to be personalized. It should reflect the shape and proportions, the kinematic properties, as well as the textural appearance of its real-world equivalent. In this paper, we present a novel spatio-temporal approach to create a personalized avatar from multi-view video data of a moving person. The avatar's geometry is generated by shape-adapting a template human body model. Its surface texture is assembled from multi-view video frames showing arbitrary different body poses. consistent surface texture for the model is generated using multi-view video frames from different camera views and different body poses. With our proposed method photo-realistic human avatars can be robustly generated.
Keywords: avatar creation, shape deformation, texturing, virtual reality