Showing papers on "Virtual machine published in 1995"

QuickTime VR: an image-based approach to virtual environment navigation

Abstract: Traditionally, virtual reality systems use 3D computer graphics to model and render virtual environments in real-time. This approach usually requires laborious modeling and expensive special purpose rendering hardware. The rendering quality and scene complexity are often limited because of the real-time constraint. This paper presents a new approach which uses 360-degree cylindrical panoramic images to compose a virtual environment. The panoramic image is digitally warped on-the-fly to simulate camera panning and zooming. The panoramic images can be created with computer rendering, specialized panoramic cameras or by "stitching" together overlapping photographs taken with a regular camera. Walking in a space is currently accomplished by "hopping" to different panoramic points. The image-based approach has been used in the commercial product QuickTime VR, a virtual reality extension to Apple Computer's QuickTime digital multimedia framework. The paper describes the architecture, the file format, the authoring process and the interactive players of the VR system. In addition to panoramic viewing, the system includes viewing of an object from different directions and hit-testing through orientation-independent hot spots. CR

Virtual reality on a WIM: interactive worlds in miniature

Abstract: This paper explores a user interface technique which augments an immersive head tracked display with a hand-held miniature copy of the virtual environment We call this interface technique the Worlds in Miniature (WIM) metaphor By establishing a direct relationship between life-size objects in the virtual world and miniature objects in the WIM, we can use the WIM as a tool for manipulating objects in the virtual environment In addition to describing object manipulation, this paper explores ways in which Worlds in Miniature can act as a single unifying metaphor for such application independent interaction techniques as object selection, navigation, path planning, and visualization The WIM metaphor naturally offers multiple points of view and multiple scales at which the user can operate, all without requiring explicit modes or commands Informal user observation indicates that users adapt to the Worlds in Miniature metaphor quickly and that physical props are helpful in manipulating the WIM and other objects in the environment

Taking steps: the influence of a walking technique on presence in virtual reality

Abstract: This article presents an interactive technique for moving through an immersive virtual environment (or “virtual reality”). The technique is suitable for applications where locomotion is restricted to ground level. The technique is derived from the idea that presence in virtual environments may be enhanced the stronger the match between proprioceptive information from human body movements and sensory feedback from the computer-generated displays. The technique is an attempt to simulate body movements associated with walking. The participant “walks in place” to move through the virtual environment across distances greater than the physical limitations imposed by the electromagnetic tracking devices. A neural network is used to analyze the stream of coordinates from the head-mounted display, to determine whether or not the participant is walking on the spot. Whenever it determines the walking behavior, the participant is moved through virtual space in the direction of his or her gaze. We discuss two experimental studies to assess the impact on presence of this method in comparison to the usual hand-pointing method of navigation in virtual reality. The studies suggest that subjective rating of presence is enhanced by the walking method provided that participants associate subjectively with the virtual body provided in the environment. An application of the technique to climbing steps and ladders is also presented.

Simulator Sickness in Virtual Environments.

Abstract: : Virtual Reality (also known as Virtual Environment or VE) technology shows many promising applications in areas of training, medicine, architecture, astronomy, data handling, teleoperation, and entertainment. A potential threat to using this - technology is the mild to severe discomfort that some users experience during or after a VE session. Similar effects have been observed with flight and driving simulators. The simulator sickness literature forms a solid background for the study of sickness in virtual environments and many of the findings may be directly applicable. This report reviews literature concerning simulator sickness, motion sickness, and virtual environments. Forty factors that may be associated with simulator sickness in virtual environments are identified. These factors form three global categories: subject, simulator, and task. The known and predicted effects of these factors on sickness in VEs are discussed. A table summarizes the information presented in this report. The information can be used as a guide for future research concerning simulator sickness in virtual environments.

Virtual Environment Interaction Techniques

Abstract: Virtual environments have shown considerable promise as a natural (and thus it is hoped more effective) form of human-computer interaction. In a virtual world you can use your eyes, ears, and hands much as you do in the real world: move your head to set your viewpoint, listen to sounds that have direction, reach out your hands to grab and manipulate virtual objects. Virtual worlds technologies (such as head-tracking and stereo, head-mounted displays) provide a better understanding of three-dimensional shapes and spaces through perceptual phenomena such as head-motion parallax, the kinetic depth effect, and stereopsis. Precise interaction, however, is difficult in a virtual world. Virtual environments suffer from a lack of haptic feedback (which helps us to control our interaction in the real world) and current alphanumeric input techniques for the virtual world (which we use for precise interaction in the computer world) are ineffective. We are unfamiliar with this new medium we work in; we do not fully understand how to immerse a user within an application. Before we can create virtual world solutions to real world problems we must learn how to interact with information and controls distributed about a user instead of concentrated in a window in front of him. We must identify natural forms of interaction and extend them in ways not possible in the real world.

The Responsive Workbench: a virtual work environment

Abstract: In this virtual environment, customized scientific visualization tools offer specialists new ways to work cooperatively, which opens the door to more comprehensive analysis and, perhaps, reduced costs. Implementing the Responsive Workbench required close attention to several important elements: its components, a typical setup, the user interface, feedback speed and real-time rendering. >

RING: a client-server system for multi-user virtual environments

Abstract: This paper describes the client-server design, implementation and experimental results for a system that supports real-time visual interaction between a large number of users in a shared 3D virtual environment. The key feature of the system is that server-based visibility algorithms compute potential visual interactions between entities representing users in order to reduce the number of messages required to maintain consistent state among many workstations distributed across a wide-area network. When an entity changes state, update messages are sent only to workstations with entities that can potentially perceive the change—i.e., ones to which the update is visible. Initial experiments show a 40x decrease in the number of messages processed by client workstations during tests with 1024 entities interacting in a large densely occluded virtual environment.

Method and apparatus for reducing instability in the display of a virtual environment

Abstract: The present invention relates to a method for reducing image instability in a virtual environment due to the transport delay of the image generator and other components of the system. A method is given for determining the error in the generated virtual environment and using this error for shifting the image on the display device thus providing a more accurate and more stable representation to the viewer.

Virtual environments for treating the fear of heights

Abstract: Can virtual environments help elicit fearful feelings so they can be treated? This article shows how therapists and computer experts used them to do just that. We describe a pilot study that used virtual reality graded exposure techniques to treat acrophobia-the fear of heights. We specifically address two issues: the extent to which we were able to make subjects feel that they were actually present in height situations, and the efficacy of the treatment conducted using virtual height situations. >

Haptic interfaces for virtual environment and teleoperator systems

Abstract: Spend your time even for only few minutes to read a book. Reading a book will never reduce and waste your time to be useless. Reading, for some people become a need that is to do every day such as spending time for eating. Now, what about you? Do you like to read a book? Now, we will show you a new book enPDFd haptic interfaces for virtual environment and teleoperator systems proceedings that can be a new way to explore the knowledge. When reading this book, you can get one thing to always remember in every reading time, even step by step.

Exploiting reality with multicast groups

Abstract: This article describes our investigation into developing large distributed simulations. The architecture we describe logically partitions virtual environments by associating spatial, temporal, and functional classes with network multicast groups. We exploit the actual characteristics of the real-world large scale environments being simulated by focusing or restricting an entity's processing and network resources to its area of interest via a local area-of-interest manager. For example, a simulated infantryman in a virtual environment doesn't need to know the condition of a simulated truck 20 virtual kilometres away. >

Hypervisor-based fault tolerance

Abstract: Protocols to implement a fault-tolerant computing system are described. These protocols augment the hypervisor of a virtual-machine manager and coordinate a primary virtual machine with its backup. The result is a fault-tolerant computing system. No modification to hardware, operating system, or application programs is required. A prototype system was constructed for HP's PA-RISC instruction-set architecture. The prototype was able to run programs about a factor of 2 slower than a bare machine would.

The ALIVE system: full-body interaction with autonomous agents

Abstract: The cumbersome nature of wired interfaces and the limited nature of the interaction with graphical objects has so far limited the range of application of virtual environments. We discuss the design and implementation of a novel system, called ALIVE, which allows wireless full-body interaction between a human participant and a rich graphical world inhabited by autonomous agents. Based on results obtained with real users, the paper argues that this kind of system can provide more complex and very different experiences than traditional virtual reality systems. The ALIVE system significantly broadens the range of potential applications of virtual reality systems; in particular the paper discusses novel applications in the area of training and teaching, entertainment and last but not least, digital assistants or interface agents. >

Vision based hand modeling and tracking for virtual teleconferencing and telecollaboration

Abstract: The authors present a hand model that simultaneously satisfies both the synthesis and analysis requirements of model based compression. The model can be fitted to any person's hand and can be done using a single camera. Once the model is fitted to a real human hand, it is then used in several tracking scenarios in order to verify its effectiveness. With successful tracking achieved, the model is ready to be incorporated into a virtual environment or model based compression scheme such as sign language communication over telephone lines or virtual teleconferences over computer networks at very low bit rates and at very high image quality. >

The effect of update rate on the sense of presence within virtual environments

Abstract: The current study was done to investigate the effect of varying the update rate of a computer-generated simulation (5, 10, 15, 20, 25 Hz) on the sense of presence within stereoscopic virtual environments. Thirteen subjects navigated a virtual representation of Stonehenge and were asked to search for a rune, inscribed upon the wall of one of Stonehenge's edifices. After performing the search task, subjects completed a questionnaire designed to assess their level of presence within the virtual environment. The results indicated that the subjective report of presence within the virtual environment was significantly less using an update rate of 5 and 10 Hz when compared to update rates of 20 and 25 Hz. Furthermore, the reported level of presence using a 15 Hz update rate was similar to the reported level of presence using update rates of 20 and 25 Hz thus indicating that computational resources could be saved using a slower update rate while maintaining a given level of presence. In addition, a factor analysis procedure indicated that the 13 questions designed to assess the subjects sense of presence within virtual Stonehenge could be grouped into three factors: (1) virtual presence, (2) navigation within the virtual environment, and (3) knowledge of real world surroundings while in the virtual world. Finally, comments on a descriptive model of presence within virtual environments are presented.

A two-handed interface for object manipulation in virtual environments

Abstract: A two-handed direct manipulation VE virtual environment interface has been developed as an intuitive manipulation metaphor for graphical objects. A new input device called ChordGloves introduces a simple technique for rapid and repeatable gesture recognition; the Chordgloves emulate a pair of 3-D mice and a keyboard. A drafting table is isomorphically mapped into the VE and provides hand support for 2-D interface techniques, as well as a reference frame for calibrating the mapping between real and virtual worlds. A cursor gravity function is used to grab vertices, edges, or faces and establish precisely aligned differential constraints between objects called anchors. The capability of subjects to translate, rotate, scale, align, and glue objects is tested with a puzzle building task. An approximation of the puzzle task is done in Adobe Illustrator to provide a performance reference. Results and informal user observations as well as topics for future work are presented.

Methods for safe and efficient implementations of virtual machines

Abstract: An efficient method for implementing a safe virtual machine, in software, that embodies a general purpose memory protection model. The present invention runs on any general purpose computer architecture and will run an executable that has been developed for the virtual machine. The present invention compiles the executable into the native instructions of the hardware. During the compilation, specialized code sequences are added to the code using a technique called software fault isolation. A set of allowed behaviors and a set of responses to the undesirable actions will be created and written to memory. A series of optimizations are applied so that the translated code executes at nearly the native speed of the architecture, but the fault isolation sequences prevent it from engaging in undesirable actions. In particular, the memory protection model is enforced, providing the same level of protection that customarily requires hardware support to enforce efficiently.

The virtual treadmill: a naturalistic metaphor for navigation in immersive virtual environments

Abstract: This paper describes a metaphor that allows people to move around an immersive virtual environment by “walking in place”. Positional data of participants’ head movements are obtained from a tracking sensor on a head-mounted display during a training session, where they alternate between walking in place and a range of other activities. The data is fed to a neural net pattern recogniser that learns to recognise the person’s walking in place behaviour. This is used in a virtual reality system to allow people to move through the virtual environment by simulating the kinds of kinesthetic actions and sensory perceptions involved in walking. An experiment was carried out to compare this method of navigation with the familiar alternative that involves using a hand-held pointing device, such as a 3D mouse. The experiment suggests that the walking in place method may enhance the participant’s sense of presence, but that it is not advantageous with respect to the efficiency of navigation.

MPVM: A Migration Transparent Version of PVM

Abstract: Parallel Virtual Machine (PVM) is a widely-used software system that allows a heterogeneous set of parallel and serial UNIX-based computers to be programmed as a single distributed-memory parallel machine. In this paper, an extension to PVM to support dynamic process migration is presented. Support for migration is important in general-purpose workstation environments since it allows parallel computations to co-exist with other applications, using idle-cycles as they become available and off-loading from workstations when they are no longer free. A description and evaluation of the design and implementation of the prototype Migratable PVM system is presented together with some performance results.

Guided navigation of virtual environments

Abstract: This paper presents a new methodology for navigating virtual environments called “The River Analogy.” This analogy provides a new way of thinking about the user's relationship to the virtual environment; guiding the user's continuous and direct input within both space and time allowing a more narrative presentation. The paper then presents the details of how this analogy was applied to a VR experience that is now part of the permanent collection at the Chicago Museum of Science and Industry.

Object associations: a simple and practical approach to virtual 3D manipulation

Abstract: This paper describes a software framework to aid in designing and implementing convenient manipulation behaviors for objects in a 3D virtual environment. A combination of almost realistic-looking pseudo-physical behavior and idealized goal-oriented properties, called object associations, is used to disambiguate the mapping of the 2D cursor motion on the display screen into an appropriate object motion in the 3D virtual world and to determine a valid and desirable final location for the objects to be placed. Objects selected for relocation actively look for nearby objects to associate and align themselves with; an automated implicit grouping mechanism also falls out from this process. Concept, structure, and our implementation of such an object association framework in the context of the Berkeley Soda Hall WALKTHRU environment are presented.

Realizing the full potential of virtual reality: human factors issues that could stand in the way

Abstract: Reviews several significant human factors issues that could stand in the way of virtual reality realizing its full potential. These issues involve maximizing human performance efficiency in virtual environments, minimizing health and safety issues, and circumventing potential social issues through proactive assessment.

NPSNET: a multi-player 3D virtual environment over the Internet

Abstract: in the Proceedings of the 1995 Symposium on Interactive 3D Graphics, 9 - 12 April 1995, Monterey, California.

Exploiting position history for efficient remote rendering in networked virtual reality

Abstract: Distributed virtual reality systems require accurate, efficient remote rendering of animated entities in the virtual environment. Position, velocity, and acceleration information about each player is maintained at the player's local machine, but remote hosts must display this information in real-time to support interaction between users across the network. Prior applications have transmitted position information at the local frame rate, or they have relied on dead-reckoning protocols using higher derivative information to extrapolate entity position between less frequent updates. These approaches require considerable network bandwidth and at times exhibit poor behavior. This paper describes a position history-based protocol whose update packets contain only position information. Remote hosts extrapolate from several position updates to track the location and orientation of entities between infrequent updates. Our evaluation suggests that the position history-based protocol provides a network-scalable solution for generating smooth, accurate rendering of remote entities.

Visualization and debugging in a heterogeneous environment

Abstract: The authors' experiences with visualization and debugging of parallel virtual machine (PVM) applications and two of the tools they have devised to facilitate these tasks are described. One of the tools is a graphical monitoring package called Xab that can visually display PVM activities inside an application running across a network. The other is a graphical programming environment called Hence, which helps the user write, compile, execute, and trace heterogeneous distributed programs. The authors discuss their early work, the present research, and the future directions of these experimental projects. >

Stack caching for interpreters

Abstract: An interpreter can spend a significant part of its execution time on accessing arguments of virtual machine instructions. This paper explores two methods to reduce this overhead for virtual stack machines by caching top-of-stack values in (real machine) registers. The dynamic method is based on having, for every possible state of the cache, one specialized version of the whole interpreter; the execution of an instruction usually changes the state of the cache and the next instruction is executed in the version corresponding to the new state. In the static method a state machine that keeps track of the cache state is added to the compiler. Common instructions exist in specialized versions for several states, but it is not necessary to have a version of every instruction for every cache state. Stack manipulation instructions are optimized away.

Embedding the 2D interaction metaphor in a real 3D virtual environment

Abstract: Recent advances in both rendering algorithms and hardware has brought virtual reality to the threshold of being able to model realistically complex environments, e.g., the mockup of a large structure. As impressive as these advances have been there is still little that a user can do within a VR system other than look--and react. If VR is to be usable in a design setting users will need to be able to interact, to control and modify their virtual environments using virtual tools inside that environment. In this paper we describe a realistic virtual computer/personal digital assistant that we have built. To the user this virtual computer appears as a hand held flat panel display. Input can be provided to this virtual computer using a virtual finger or stylus to `touch' the screen. We migrate applications developed for a flat screen environment into the virtual environment without modifying the application code. A major strength of this approach is that we meld the naturally 3D interaction metaphor of a hand held virtual tool with the software support provided by some 2D user interface toolkits. Our approach has provided us great flexibility in both designing and implementing user interface components for VR environments, and it has enabled us to represent the familiar flat screen human computer interaction metaphor within the VR context. We will describe some applications which made use of our capability.

Comparison of human sensory capabilities with technical specifications of virtual environment equipment

Abstract: This paper presents the results of three surveys that compared the human's ability to detect and discriminate visual, auditory, tactile, and kinesthetic information with current technical specifications of virtual environment equipment. The comparison exposes limitations of current virtual environment interfaces and thus indicates areas where improvements in equipment design are needed. Furthermore, the paper presents basic definitions and units of measurement for sensory modalities, which also can be used to describe the capabilities of virtual environment equipment. Finally, the paper concludes with remarks concerning the relationship between the data presented in the three surveys and the design of virtual interfaces.

ISAAC: A Virtual Environment Tool for the Interactive Construction of Virtual Worlds

Abstract: This paper presents a description of ISAAC, the Immersive Simulation Animation And Construction program designed and built at the University of North Carolina at Chapel Hill (UNC-CH). ISAAC is a scene composition application for the interactive construction of virtual worlds. Working directly in a virtual environment, objects can be positioned, oriented and scaled using direct and indirect manipulation techniques. Object configurations are stored in ASCII files which can be used to recreate object configurations at a later date for further manipulation and interactive exploration. ISAAC is not a modeling program, worlds are created by manipulating pre-generated three-dimensional models (which can come from sources such as Computer-Aided Design programs or three-dimensional scanning devices). ISAAC has been designed to overcome some of the limitations of working in a virtual environment and to take advantage of the natural and intuitive forms of interaction available in a virtual world.