hentsche@serss0.fiu.edu (Erich Hentschel) (04/12/91)
Last term I spent some time putting together a term paper in Virtual Reality. It seems that some people might benefit from it. I would also like to get some feedback and comments on it. It is in "latex" format, so you will have to process it: latex filename, and then either view it with a dvi viewer of convert to postscript and print. There is actually two parts. Part two is the bibliography file, you'll need bibtex to get that to work with the notes. Thanks for any comments and suggestions. Erich Hentschel hentsche@serss0 Florida Intl. Univ. Miami Fl -------------- Cut Here ------------- \documentstyle[12pt]{article} \begin{document} \input{title} \pagenumbering{roman} \tableofcontents \newpage %\input{latex_commands} \newcommand{\bd} {\begin{description}} \newcommand{\ed} {\end{description}} \newcommand{\bi} {\begin{itemize}} \newcommand{\ei} {\end{itemize}} \newcommand{\be} {\begin{enumerate}} \newcommand{\ee} {\end{enumerate}} \newcommand{\ind} {\hspace*{0.0in}} \newcommand{\bl} {{\\ \vspace*{.05in} \\}} \newcommand{\blind} {\bl \ind} \newcommand{\hci} {Human Computer Interface} \newcommand{\vr} {Virtual Reality} \newcommand{\ar} {Artificial Reality} \newcommand{\ve} {Virtual Environment} \newcommand{\ccl} {Computerized Clothing} \newcommand{\vw} {Virtual World} \newcommand{\env} {environment} % \setcounter{page}{0} \pagenumbering{arabic} \section{Introduction} %\input{intro} \ind Computers have the potential to influence and change our entire civilization because computers are not simply tools that perform tasks on our behalf but actually ``computers are a medium". The nature of tools and the learning of how to use them reshapes us. \cite{KAY} \bl \ind In order for us to communicate via a medium, we must be capable of becoming the medium itself, in this way the message being communicated is not corrupted by the medium. When the user of a computer has trouble with the interface, the medium looses its effectiveness. The goal is then, to create a \hci\ that reflects the way we interact with the real world. It is here that {\bf Virtual Reality} makes its debut as a powerfull new technology that is pointing in the direction of this goal. In a \ve\ the participant establishes a direct connection with their virtual senses. The participant does not have to learn how to extract information from the medium. \cite{JACOBSON} \bl \ind There are two directions being follow in the field of \vr. Myron W. Krueger, who coined the phrase {\bf Artificial Reality}, feels that we will pursue an interface that ``merges seamlessly with the rest of our environment". \cite{KRUEGER} So the use of devices in order to interact with a computer should not be needed. The other direction is using current technology to create various devices called {\bf Computrized Clothing}.\cite{LANIER} These devices are being used to track body position, track head position, recognize voice, give force feedback, and place the user inside simulated worlds. \bl \ind % In this paper we will only consider the second direction. We will % explore the various senses being enticed in this inclusive % interface. This paper is a survey of some of the issues related to \vr\ and some of the current developments in the field. An analysis of visual perception will give us an insight of how our senses interact with the environment. We also explore some of the issues in the design of \hci s. A description of \vr\ explains how current systems operate and what devices have been created to achieve it. A view of some developments in the devices that deal with sound, force--feedback, and touch, as well as some work related to virtual entities is presented. A look of some applications should explain the exitement that \vr\ is stirring up. %%%%%%%% \section{Visual Perception} %\input{perception} \ind Our senses can be considered as perceptual systems. Our visual perception involves more than simple snapshot vision. We must also consider apperture vision, ambient vision, and ambulatory vision since Visual Awareness is panoramic and is perceived during acts of locomotion. This is the ``Ecological Approach to Perception", a new approach in the whole field of psycology.\cite{GIBSON} \subsection{ The Environment} We observe that animals are organisms that perceive and behave. Humans perceive and behave. Locomotion and behavior are continually controlled by the activities of seeing, smelling, and hearing, together with touching. The \env\ consists of the surroundings of animals, this \env\ includes other organisms in the same \env\ as well. There exists a phenomena called the ``Mutuallity of animal and \env\ ". It's similar to the analogy of the tree falling in the woods far away, does the tree make any sound as it falls? In this case surroundings are not considered and \env\ when there is not some animal to perceive it. Information about the self accompanies information about the environment. One perceives the \env\ and coperceives oneself. \subsection{The Ambient Optic Array} \ind The central concept of ecological optics is the {\bf ambient optic array} at a point of observation. To be an {\em array} means to have an arrangement, and to be {\em ambient at a point} means to surround a position in the environment that could be occupied by the observer. % Visual Kinesthesis, the Optical information gathered when movement takes place can be analyzed by the following types of movement. \bd \item [Head Turning -- ] The sweeping of the field of view over the ambient array. \item [Limb Movement -- ] Manipulation. Protusion of special shapes and the field of view. \item [Locomotion -- ] The flow of the ambient array. \ed \subsection{The Mediums} Our planet is formed by air, water, and earth. These are states of matter gas, liquid, and solid respectivelly and the interface between them constitutes a surface. They exhibit the following characteristics: \be \item Gas and liquid states afford locomotion to animate bodies, thus they are mediums for animal locomotion. Solids present us with great resistance. \item Gas or liquid mediums are generally transparent, transmitting light. Solids are generally opaque, absorbing or reflecting light. A homogeneous medium thus affords vision. A terrestrial medium is not only a region where light is transmitted but it also reverberates. \item Air and water transmit vibrations or pressure waves outward from a mechanical event, a source of sounds, thus it affords hearing, listening to the vibratory event (sound). \item The medium of air or water permit rapid chemical diffusion whereas the earth does not. The medium thus affords smell by allowing molecules to dissolve or diffuse outward from a source. \ee \ind The medium in which animals live is at the same time the medium for light, sound, and odor coming from sources in the \env . It contains information about objects and animals in the \env\ that reflect light, vibrate or are volatile. Instead of geometrical points and lines we have points of observation and lines of locomotion. As the observer moves from point to point the information in the \env\ changes accordingly. Each potential point of observation in the medium is unique in this respect. \section{Human Computer Interface} %\input{hci} \ind ``The Art of Human Computer Interface Design" edited by Brenda Laurel, contains a wealth of information that sets up the stage for \vr\ interface design and beyond. \cite{LAURELBOOK} Many issues are presented to help us understand and explore the possibilites in the development of \hci s. %\subsection{User Interface: A Personal View} \subsection{On User Interfaces} \ind The most important concept that I found throughout my research has staggering psychological implications. Namely, as McLullen put it in ``Understanding Media", the computer is a medium. A seemingly harmless statement, but the mere usage of a medium has shown to have cause profound changes on those who use it. Entire civilizations can be reshaped thus. Other examples that substantiate this claim are the printing press and the microscope. In relation to \vr\ it seems that we are one step closer to making this medium right for unforseeable events to take place. \cite{KAY} \vr\ takes the user to a place, it connects directly with the participants perceptory senses. It has the potential of being the \hci\ that can be used by anybody, in particular those who are completely computer illiterate. In order to communicate the medium used must not interfere. Interfaces seem to get in the way. \cite{NORMAN} If the user has to spend part of her or his concentration , however minimal, figuring out how to use the medium, the message that was to be transmitted will be corrupted. The user must become the medium so that the message is retrieved effectivelly. %\subsection{Negroponte} \cite{NEGROPONTE} \blind Humans have certain cognitive facilities, in particular the doing mentality, the iconic mentality, and the symbolic mentality. User interfaces should cater to these cognitive facilities. \cite{NEGROPONTE} The phrase ``doing with images makes symbols" was mentioned in relation to the enactive, iconic, and symbolic modes. Also the mouse was related to the enactive, the icons and windows to the iconic, and SMALLTALK to the symbolic. \cite{KAY} In other words, SMALLTALK was designed with these modes in mind, catering directly to them. %\subsection{What's the Big Deal about Cyberspace?} \blind Virtual \env s should enable the participants to visualize symbolic worlds in new ways. The capability for total sensory transport give cyberspace the potential to become a historical phenomena. The cyberspace experience is bound to transform us because its an undeniable reminder of the fact that our normal state of conciousness is itself hyper--realistic--simulation. We live in self erected mental models. We are experts at creating virtual worlds. \cite{RHEINGOLD} \subsection{Virtual Agents} \ind Another issue that was brought out extensively and in various disguises was that of special agents. These agents should be able to perform tasks that are either to time consuming or that require considerable amount of strategy to perform. This should allows us to concentrate on the task and not on what tools are needed to complete the task. We should expect to have direct manipulation of these agents, who can execute complex functions, filter information, and intercommunicate in our interests. \cite{KAY} %\subsection{Interface Agents: Metaphors with Character} \blind ``An interface agent can be defined as a character, enacted by the computer, who acts on behalf of the user in a \ve ." Some arguments against these agents exist. For example, a virus--agent, but the argument fails in that being a virus is a characteristic of the agent. Because there are rampant computer viruses does not mean that one will stop using their computer. There is also ethical questions being asked. In general, not everyone should have agents. Only those people who choose to use them should have them. There are even those who are against the agents for antropomorphic reasons. Some agents have antropomorphic characteristics, users might not be able to deal with this, but on the other hand we can associate with agents who are competent, successfull, and are capable of doing work on our behalf. They should provide us with expertise, skill, and labor. \cite{LAUREL} \subsection{Guides} \cite{OREN} A hypermedia application chose the guides metaphor to navigate through their hypermedia database management system. The application covered a period in US history from 1800 to 1850. In order to explore any area of the history you have to choose among a variety of guides to show you around. The following is a compilation of some of the problems and observations obtained from users of the guides. \bi \item The guides did not seem able to respond to user when asked why they had been brought to a particular place. \item The users wanted to know if the story was being told from the guide's point of view. \item Some users got upset and felt betrayed by their guides. \item Some users did not allow the observers to be in the same room while they were traveling with the guides, these people felt that they were having private conversations with the guide and no one should be listening. \item Users want characterization in the guides. \ei This application is an example of how agents can be used in our \hci\ as virtual agents with antropomorphic behavior. \section{Virtual Reality} %\input{virtual} \ind {\bf Virtuality} is a metasense that synthezises our five physical senses and the experience of time. The synthesis of sensory inputs give us a sense of time and place.\cite{BRICKEN} % check to make sure about this cite \vr\ is explained as follows: ``A computer simulation of reality that can surround a person that is created with {\bf computerized clothing}....it's an externally perceived reality that you perceive through your sense organs and the physical world." \cite{LANIER} \bl \ind The user is placed inside the simulated world and can experience 3D sights and sounds, and perceive tactile and haptic sensations. The user can also interact with the environment, that is interact with other entities and manipulate objects in the simulated world. The following sections describe how \vr\ can be accomplished, how some current systems have been built, and how to deal with \vr . \subsection{ \ccl\ } \vr\ deals with various of our senses using \ccl . These behavior transducers are devices that map natural behavior to digital information. \cite{BRICKEN} The following sections describe some of these devices. \subsubsection{Head Mounted Display} This device has as its primary function to convince the user that she, or he, is inside the virtual world. It provides the user with a 3D stereoscopic view of the virtual world. Head mounted displays generally consist of two color computer displays, one for each eye. The images displayed are different to give the illusion of depth. Straps are used to mount the device on the users head, like a pair of goggles. All external light is blocked out. The overall effect is that of complete inclusion in the \ve\ where the user participates in the medium. Instead of seeing or looking at a picture we find ourselves in a place. Head mounted display devices can include trackers, sensors, voice recognition, and audio capabilities. \bl \ind Commercially available Head Mounted Displays include: \bi \item Eyephone system {\bf VPL}. With 86000 pixels, 100 degrees field of view, and a price of \$ 9,400. It includes a Polhemous tracker. \item Cyberface II from {\bf LEEP Systems}. More than 125000 pixels, 150 degrees field of view, and price of \$ 8,100. Does not include tracker. Includes integral headphones and additional controls. \item BOOM II from {\bf Fake Space Labs}. Monochrome 300000 pixels, 100 degrees field of view and a price of \$ 27,000. \ei \subsubsection{Position Sensors} \ind Head mounted displays have position sensors attached to it. The system can detect the position and orientation of the head. Moving your head in one direction causes the system to display the images on the screens moving in the opposite direction. This creates the effect of moving inside the virtual environment. Most position sensors use magnetic fields. The most popular position sensors are being manufactured by {\bf Pholemus Inc.}. \bl \ind The Data Glove (VPL) is a customized glove. Position sensors run along the back of each finger. Fiber Optiks are used to to detect angles between different parts of the fingers. The cheapest device commercially available today is The Power Glove (MATTEL). It uses ultrasonic detectors and electro conductive ink. We will look at the following devices in more detail when we look at developments in force--feedback. The Force--Feedback arm (UNC) which applies forces on the user, such as resistance, giving haptic sensations and The Master Manipulator (University of Tsukuba). \subsubsection{Ear Phones} \ind Another target sense in a virtual environment is the auditory system. The ear phones produce 3D sounds. This is achieved by filtering digital audio and position sounds in 3D space. Sounds follow their assigned objects as the user passes by. The main sound control and processing system available is a 320 MIPS, real--time signal processor know as the convolvotron, designed by Scott Foster. We will also look at this in more detail in the section that deals with digitizing sound. \subsection{\vr\ Systems} Various \vr\ systems have been implemented. These systems offer \vr\ exploration and interaction via \ccl . Special hardware and software components are presented giving us a good idea of the availability of systems as well as the power they should provide us with. \bi \item The Virtual Enironment Workstation {\bf (VIEW) } is a project at {\bf NASA Ames research center}. This system started as project for developing a high level simulation for AIR FORCE pilots. They have developed various applications such as the Virtual Wind Tunnel and SIMNET. Their system uses a head mounted display and has auditory, speech and gesture interaction capabilities. The head mounted display consists of two LCD screens with 640x220 pixels resolution with wide--angle optics, which mimic the human binocular visual capabilities. The device also has tracking sensors attached to it. It enables high performance, real--time 3-D graphics presentation at up to 30 frames per second as required to update the display in coordination with the users new orientation and position. A {\bf VPL} data glove provides absolute position and orientation of the hand, this information is used to handle a virtual hand which can manipulate other virtual objects. The system recognizes gestures from the hand and can interpret these as commands. The Covolvotron auditory system augments or supplies information to the \ve . The system provides 3-D stereoscopic sound. The VIEW system includes a speech recognition device for voice input. \cite{FISHER} \item The Reality Built for Two {\bf (RB2) } system. \cite{GROOT}, \cite{HAYES}, \cite{VPL} This is the system that has been developed by {\bf VPL Research} and is commercially available. The system allows for two users at once in a virtual space. This system consists of the following components: \bd \item [Hardware -- ] One VPL {\em DataGlove} which converts hand motion into computer readable form. The position sensors on the glove form an integrated {\bf Polhemus } tracking system. It supports RS232 and RS 422 serial input and output. One {\em EyePhone} is the head mounted display incorporating color LCD's, {\bf Polhemus} tracking system, a microphone, and audio headphones. The video images is enhanced by a proprietary optical diffusion element. An {\em AudioSphere} is audio system providing 3-D sounds. It uses the {\bf Convolvotron} and software that provides basic position and motion sound rendering, including distance rolloff, Doppler shift, and more. A design and control Macintosh workstation and two Silicon Graphics Power Series workstations provide the power to build, use, play, and run \ve . The components are networked together by a combination of Ethernet and a proprietary synchronization bus. Since one IRIS is needed for each each, we would need four workstations to have two users in the same \ve , as well as \ccl\ for each one. \item [Software -- ] (On Macintosh workstation). The {\em RB2 Swivel} modeling software from Macintosh, is a tool for defining the shapes, layout, linkages, and motion constraints of the 3-D objects in a \vw . {\em Body Electric}, a real--time simulation program for specifying object behavior by Macintosh, incorporates advanced visual programming and signal processing features. Its an incremental compiler generating high speed simulation code that allows changes to be made interactively, while a simulation is running. (On the graphics workstations). {\em Issac} software renders the \ve\ in real--time. {\em Isacc} and {\em Body Electric} communicate while a simulation is running. \ed \item {\bf Autodesk} has a system called {\bf Cyberspace}. It's a 386--Based PC and a custom video board. One of the great feature about this system is that is used {\em AutoCAD} as it's basic software. Any thing that can you can build with {\em AutoCAD} can be explored with Cyberspace. \cite{HAYES} \item At {\bf University of North Carolina} the {\bf Pixel Planes} parallel processing system was developed. This system can do 3-D rendering in real-time by assigning one processor to each pixel of the display. \ei \section{Sound} %\input{sound} \subsection{``Real--Time Digital Synthesis of Virtual Accustic Environments"} \cite{WENZEL} A signal processing device that generates 3D sound is described. This device is being used at {\bf NASA--Ames Research Center} with their Virtual Interactive Environment Workstation. {\bf ( VIEW ) } VIEW allows the user to explore and interact with a \vw\ using a head mounted display and data glove controlled by the operators position, voice, and gestures. \bl \ind Possible applications that could benefit from using sound in a \ve\ are advanced teleconferencing systems, monitoring tele--robotic activities, and scientific visualization of multidimensional data. \bl \ind The process involves synthesizing localized sounds. Finite Impulse Response {\bf (FIR)} filters are placed around a would be user's ear drums at intervals of 15 degrees azimuth and 18 degrees elevation for a specific range. A total of 144 FIR filters are positioned. A map of location filters is constructed and downloaded to a real time digital signal--processor. This device is called the {\bf convolvotron}, designed by Scott Foster from {\bf Crystal River Engineering}. It convolves an analog signal with filter coefficients determined from the FIR map and head position. The signal is placed in perceptual 3--Space of the user. Motion trajectories and static locations at higher resolution than the sampling are interpolated. Perceptual accuracy of the basic technique has been confirmed by static sources. Preliminary data suggest that using non--listener--specific transforms to achieve synthesis of localized cues is at least feasible. \section{Force -- Feedback} %\input{force} This section explores some of the ongoing research in the area of force feedback. Force feedback gives users haptic or tactile sensations. This feature should aid users their \vr\ when interacting with objects or entities in the \vr . by adding and added input to the sense of touch and feel. \subsection{``Artificial Reality with Force--feedback. Development of Desktop Virtual lSpace with Compact Master Manipulator"} \cite{IWATA} This paper discusses an interface device fo artificial reality with force feedback for the manipulation of virtual objects at {\bf University of Tsukuba}. First a brief description of \ar\ is given leading to the following statement: ``methods presenting tactile information have not been sufficiently developed". A description of existing tactile input devices is given, a glove, a 3-D mouse, and the master manipulator, and the disadvantages of these are explained. The author has developed a virtual object manipulation system on a desktop computer. The system consists of an image generator system and a master manipulator with 9 degrees--of--freedom and tactile input. \bi \item Image Generator Subsystem. A specialized graphics computer is used, the TITAN, which has 2 CPU boards and its peak performance is 32 MIPS, 32 MFLOPS. The position and orientation of the hand are described in a coordinate system fixed in the \vw . A virtual hand is drawn that consists of 100 Gouraud shaded polygons. The user can only see the virtual hand, the user must look into a mirror that is placed at 45 degrees from the screen. \item Master Manipulator for tactile input and reaction force generator subsystem. A {\em parallel } manipulator consist of two triangles at different levels and 6 cylinders connecting every corner of one triangle with two corners of the other triangle. The length of the cylinders can be controlled. These manipulators lack backdriveability and use a small working volume. The author and a team at University of Tsukuba developed a new {\em link} manipulator. The manipulator uses pantograph link mechanisms instead of linear accutators, it improves the working volume and backdriveability. The top platform of the manipulator is fixed to the palm of the operator, enabling the user to move the hand and fingers independently. The thumbs's working angle is 120 degrees, the other fingers is 90 degrees. The middle, ring, and little fingers work as a unit. The manipulator applies forces to the fingers and palm of the operator. \ei The hand is divided into 16 control points and the distance between these points and the surface of virtual objects is calculated. To grab an virtual object you must {\em touch} the virtual object with the thumb and a finger. Objects can have attributes such as solidity. A rigid body produces a reaction force with maximum possible torque. A force and movement vector is computed at the palm with respect to the palm and the virtual object. Tactile sensations are limited, in particular very detailed ones such as surface texture, future enhancements should consider this. Some applications of this systems include the manipulation of virtual prototype products and the choreography for 3-D animated characters. \subsection{``Project GROPE -- Haptic Displays for Scientific Visualization"} \cite{GROPE} The goal of this project was to develop a haptic display for 6-D of interaction in the design of protein molecules. This work was done at {\bf University of North Carolina at Chapel Hill}. The project started back in 1967 and is has gone through a 2-D stage, then a 3-D stage, then a 6-D stage with a simple task, and finally a full 6-D molecular docking system. The word haptic is defined as ``pertaining to sensations such as touch, temperature, pressure, etc. mediated by skin, muscle, tendon, or joint." This system works directly with scientific visualization, the area of computer graphics which aims to improve our understanding of scientific phenomena by enhancing scientists' perception of real or predicted models. The haptic display improves perception and understanding of the world models and the force fields being simulated. Chemists report having a new understanding of why a particular drug docks well or poorly. They can reproduce the true docking positions for known drugs easily and seem to find good docks for drugs whose true docking positions are unknown. An improvement in situation awareness has been reported by the users. The pharmaceutical industry should benefit from the use of haptic displays, but the development in this industry will be very slow. \section{Virtual Camera Control} %\input{virtualcamera} \subsection{``Exploration and Virtual Camera Control in Virtual Three Dimensional Environments"} \cite{WARE} Evaluation of three distinct metaphores for exploration and virtual camera control in \ve s using six degrees of freedom was done by the Computer Graphics and Animation Group at The Media Laboratory {\bf Massachusetts Institute of Technology}. The metaphors are: \be \item Eyeball in hand, the image that the eye sees is mapped on the screen. A position tracker is used to determine the hand position and orientation. The view is from the vantage point of the hand held eye. \item Scene in hand, the scene is translated and rotated in relation to a 3--Space mouse. \item Flying vehicle control, the 3--Space mouse is used as a navigation control device. The user can fly forward, backward, through objects, up, down, etc. \ee The motion path can be recorded and played back. The system provides the user with an interface for exploring virtual graphical environments. Descriptions of other methods are discussed. Observations about the task: \bi \item Racing the viewpoint in the \ve\ has six degrees of freedom, three for position and three for angular placement. \item Exploration of the \ve\ can be done by navigating a viewpoint in the environment. \item Moving a viewpoint is isomorphic with moving the environment with respect to the viewpoint. \ei The product was used on three toy environments, a cube, a maze, and a scene of traffic signs. Seven subjects were experimented with. Intensive interviews provided the following results. The results regarding constructs and affordances, cognitive properties and movie making insight for each of the metaphors. Some metaphors are better suited for different tasks, such as flying vehicle to navigate the maze and scene in hand for the cube. Further work expects to extend the exploration with manipulation of objects in the environment. The eyeball in had offers no such extension while the flying vehicle and scene in hand seem good candidates. \section{Virtual Actors} %\input{virtualactors} If telepresense is to become a reality, we must understand how to deal with what Alan Kay once called ``software robots" as well as with actual robots at remote locations. These robots will have to be able to perform tasks without our intervention, but there will be instances when we will want to direct them and guide them through problems that they are not ready to deal with. This section contains information that will be important in the understanding of the problems that need to be solved in this area. \subsection{``Control of a Virtual Actor: The Roach"} \cite{ROACH} A \ve\ system is discussed which supports simulations of virtual actors, by Computer Graphics and Animation Group at the Media Laboratory {\bf Massachusetts Institute of Technology}. The actors are provided with capabilities to perceive the virtual environment that they inhabit, they can be directed or react to changes in their habitat. Design, training, and testing can be done in a workplace of prototype virtual agents in virtual environments. %The actors behavior will be driven by their perception of %the environment, they will not have highly cognitive and %motor skills. In particular the actor chosen simulates the behavior of a cockroach. The virtual actor can wonder around the simulated environment interacting with multiple simulations. The roach can perceive changes in the environment, it reacts to commands, it runs away from a grabbing hand, or follows the hand around. The roach can display a wide variety of functional behaviors. There is no other system that supports virtual actors, distributed simulations, and interactions among various simulations. \blind The behavior of the virtual actor is defined by the {\em sensori--motor level}, which consists of muscle groups, motor organs, and motor organ systems. The {\em reactive level} give the virtual actor the power to select and reponds approprietly to environment changes. \bi \item The {\em sensori--motor level} consists of a gait controller and kinematic motor programs. The gait controller is a system that coordinates motor organ activity. Each leg has an oscillator which triggers steps. There are time and phase relationships that the oscillators must maintain. Reflexes reinforce the basic oscillator patterns and add adaptability of the gait. The kinematic motor programs control the muscle groups at the joints. This produces body and limb motions which result in locomotion and stance of the roach. The behavior of the roach is observed as locomotion. \item Implementation. Gait oscillators and reflexes set states for the motor programs. The kinematic programs generate the locomotive behavior. Parameters are set with scripting commands at the reactive level. A task level program can be used to specify goals for the roach to fullfill. This level also contains tools to control the sensori-motor level, such as parameter setting sliders and a data glove to instill reactive behavior. \item In the {\em reactive level} messages are passed to the virtual actor which in turn react to them. The perception of the environment is simulated as a constraint network where events are associated with motor acts. The actual exchange of information is implemented using {\em bolio}, which is the graphical simulation platform which manages a global object database and implements distributed message processing. \ei The authors feel that the design of virtual actors should be guided by research into the behavior and neural organization of actual animals. The system simulates basic behavior only. \section{Applications} %\input{applications} \vr\ is a place for exploration, navigation, communication, and creativity. Participants will find themselves with capabilities never before available to them. The potential for breakthroughs and discoveries in completely unrelated areas is explosive. The applications once inside \vr\ seem never ending. First we will see some current applications that are fully developed or are being researched, then some applications that have been predicted by experts in the field of \vr\ will be presented. \subsection{Current Applications} \bi \item Architectural Design. When MIT's new School of Computer Science building was designed, at Chappel Hill, North Carolina, a virtual version was created. It was used to explore the architectural structure prior to constructing the building. It was determined that a wall was not right and a visit to the \vw\ convinced the architect to make some adjustments to the design.\cite{MINSKY1} Other virtual buildings have been used for advertizing. Exploration fo \vw\ has limitless applications. \item Scientific Visualization. \bi \item A Virtual Wind Tunnel is an environment for visualization and interface for exploring and understanding the output of Computational Fluid Dynamics. Virtual Fluid flow around a body is simulated. Tasks that are simply impossible to do in a real wind tunnel can now be experimented with in the Virtual Wind Tunnel. This application is being implemented at NASA Ames Research Center. \cite{USELTON} \item Project GROPE is a haptic display for molecular forces. This system was developed to improve the process of interactive design of protein molecules. It provides the user with haptic feed--back, that is, the user can feel the forces that the molecules are exerting. Haptic displays have been found to improve in the design process as well as in the enhace the users perception of simulated worlds.\cite{GROPE} \ei \item Computer Animation. \bi \item Some \vr\ systems have capabilities of virtual object manipulation and playback of camera trajectories followed. These can be used for computer animation purposes. \cite{IWATA} \item Work with autonomous virtual actors involves giving the actors the capabilities to perceive their environment. In the case of a virtual cockroach, sensori--motor activity and reactive--behavior give the actor the freedom to roam around the simulated environment, while interaction allows a user to place obstacles, issue commands, and use a virtual hand to which the roach responds. Speed, direction, and gait parameters for locomotion can be interactively altered. Gait controlling mechanisms were used in the animation of ``Grinning Evil Death". \cite{ROACH} \ei \item Simulators. \vr\ was born as a flight simulator for improving AIR FORCE pilots' abilities in missile launching. Another such environment called SIMNET, is a tank for combat simulation. This is the most widely distributed environment today. Advanced airplane cockpits are being developed at Human Interface Technology Laboratory at University of Washington. \item The Virtual Environment Operating Shell. An environment for computer resources and communication management. In particular design kits (CAD), dynamic simulation kits, virtual world tools, processors, and behavior transducer devices are part of VEOS. \ei \subsection{Future Applications} These applications have been forseen and some of these are currently under development. \bi \item Telepresence. This topic is considered a strong suite in favor of \vr . It seems that \vr\ will be the way to establish an interface between a robot in any environment and a robot operator at some remote location. These robots have will be placed in environments which are potentially dangerous, unreachable, or impossible to do in the real world, such as nuclear reactor plants, underwater construction, space colonization, and more. The operator should be able to operate the robot as if the person was actually present at the robots site. \cite{FISHER}, \cite{RHEINGOLD} \item Televirtual conferencing. \vr\ could become the communication tools of the future that will replace the telephone. Not only will you be able to hear the person that you are talking to, but you will also be able to see them, and who knows, maybe even feel them. \cite{GROOT} \item Education. The potential for educational applications has no limits. I can think of no better way of learning geometry than being in a geometric world and seeing, touching, and hearing the geometrical objects tell me personally what they are all about. Maybe students will not go to school at all but the instructors might teleteach their classes. \item Virtual Movies. It seems as though the movie industry might be done in virtual worlds that are inclusive. The movie viewers will become part of the movies and maybe even participate by taking characters rolles as well as changing the perspective or viewpoint of the scene. \ei \section{Conclusion} %\input{conclusion} \vr\ has the raw power of making us realize that the world we live in is a model of reality that we have developed. This model has been shaped by us with the help of those who have been able to influence our perception. Out of a technologically oriented society comes this new device, the computer, and now a way to use it as a medium seems to be readily available. \vr\ users perceive an environment, their body becomes and interface, they are in a place and do not have to learn anything in order to get there. It is very possible that \vr\ will unleash a whole gamma of new discoveries in our relentless pursuit of {\em The Natural Human Computer Interface}, one that closely resembles the way we interact with the real world. \blind We have studied some of the existing \vr\ systems and many of the applications that more and more show that \vr\ has the potential to become the predecessor of the {\em ultimate interface}. Some of the current applications in \vr\ send the imagination reeling into worlds that not even Science Fiction has explored. From predicted applications telepresence seems to be the most radical one, because it seems that we will be able to perceive remote locations while we are one fixed place. One application that seems plausible would allows us to create programs in a \vw . This is a logical step to current visual programming developments. \blind Two special sections, {\em Visual Perception} and {\em \hci\ } were presented with the goal of exposing us to some the issues involved in these areas. From both of these areas the desire to look at the work of \cite{ROACH} grew from learning about {\em perception} and {\em agents}. More work that would naturally follow would include \cite{FLOCKS} and \cite{WORM}. Simulating the perception of virtual agents seems to be a most interesting and rewarding area for research. I picture virtual agents as capable of displaying locomotive behavior at higher levels than the roach as well as being able to perform specialized task on my behalf. \blind {\em Sound} and {\em Force Feedback} are both topics that directly relate to some of the research that is taking place in relation to our haptic, tactile, and auditory systems. The work in these areas adds new information to the environment, taking the \vr\ experience a step closer to total perceptory \vr . \blind \vr\ is still in its conception, we can't say that it is even in its infancy. We do not really know in which direction we will go or how long it will take. It is obvious that at this time the bottleneck that prevent us from creating a very high quality image for our \ve\ is real--time rendering. All existing \vr\ systems seem to use Gouraud shading with a specified limit in the number of polygons that can be handled in one frame. This limit is required in order to be able to render in real--time. This creates rather crude simulations, but visiting these crude \ve\ seems enough to stir the participants in search of more. \blind More difficult problem involve postion and orientation of the body of the user. At this time we can accomplish this for the head and a hand using head mounted displays and data gloves, but for the whole body we have only begun to consider the possibilities. \blind The force--feedback problem is again a difficult task. The work of \cite{GROPE} started two decades back. A lot of work still remains to be done in this area. One suggestion that seemed might work talked about covering the inside of the data glove with baloon like areas that could be inflated with a substance that could also transmit temperature at the same time. Other work that should be considered deals with detailed tactile sensation as in \cite{MINSKY2} \blind One area which seems to be unfullfilled is that of dynamic enviroment manipulation. Creating an environment while inside a \vw\ seems to be the ultimate goal in \vr\ control. \newpage \bibliography{all} \bibliographystyle{alpha} \end{document}