artificial reality

8/6/2019 Artificial Reality

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VIRTUAL REALITY

"The illusion of participation in a synthetic environment rather than external observation of such an environment. VR relies on3D, stereoscopic, head-tracked displays, hand/body tracking

and binaural sound. VR is an immersive, multi-sensory experience."

- Michael A. Gigante -

Prelude

Virtual Reality is a discipline based on a technology which allowsimmersion of sight and interaction in tri-dimensional virtualenvirons (Surrounding Areas) generated by a computer. VirtualReality is progressively attracting the attention of the engineeringworld because of its capability to potentially replace, in a short while,the physical mockups and the training scenes with equally stimulatingenvirons.

Artificial reality, Cyberspace, Virtual Reality, Virtual Worlds, VirtualEnvironments, Synthetic Environments are the synonyms.

Virtual Environment This is a term coined by Myron Krueger in the mid-1970. Krueger intended the term to mean full-body participation in

computer events that is so compelling that it is accepted asreal experience.

A Computer-Generated, 3D Spatial Environment in Which UsersCan Participate in Real-time Virtual Environments Can Be

Fully Immersive , Encompassing Worlds Augmentations (Overlay) to the Real World Through the Window Worlds (Non-immersive)

VR is still an uncertain and under-utilized technology. This is partly dueto the perceived limitations of the systems and the usability issuesassociated with them, but also, to the lack of well-documented case-studies providing evidence of any added value or cost benefits fromuse. There are still too many unanswered questions associated with

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the technology and therefore few guidelines that enable industry tomake informed decisions about implementation.

Minutiae

Metaverse and Avatars

Sometimes the 3D virtual world (Gibson matrix) is called the Metaverseand the 3D icons or appearances of characters (humans) in theMetaverse are called Avatars .

Telepresence

Real-time telepresence: A visual virtual world that you interact with. - Interactionsare reflected in the movement of some real world object.i.e. a Data Glove being moved to control a robot hand thatmoves at the same time.

Delayed telepresence: A visual virtual, world that you interact with whilerecording the interactions. When you are satisfied with the results, play theinteractions across your communications delay.

Immersion & Presence

Immersion is best thought of as from what perspective(viewpoint) am I viewing the virtual world?

Presence is the notion that the user of the virtual worldfeels present in the virtual world such that the user canperform a task or set of tasks.

Sometimes the phrase immersed in the virtual world istaken to mean the same as present in the virtual world.

Why an immersive interface?

The environment encompasses large virtual spaces A largenumber of parameters are to be manipulated by the operator Tasks are of a hands-busy nature Perspective is important

Virtual reality systems are targeted to be used in factoryautomation in the future because of remote control for a fullyautomated factory. In the virtual reality system, tactile presentationbecomes important for enhancing attendance as regards the site.

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Consequently, several tactile presentation systems have been reportedand we can find now and then commercial tactile presentation systemssuch as PHANToM . On the other hand, texture recognition is one of the important items obtained from tactile sensation. Informationobtained from the texture recognition is effective for classification of

products and inspection surface defects. Since human tactile receptors(mechanoreceptor) are distributed over the entire skin surface, thetactile presentation devices should present distributed pressure.Additionally, precise actuators capable of presenting from severalmicrons to about 100 microns are needed for presenting the surfacetexture.

Virtual training in such operations as assembling, maintenance andsupport allow the trainee to quickly acquire practice in operating. Thetrainee would carry out most of the training in the interactivesimulation where both the activity circling round the operation and the

instruments used are recreated virtually. This approach is particularlysuitable for operations where a false move, carried out in the realworld, would expose the operator (still ill-experienced in risk-taking) toa precarious situation for both people involved as well as physicalstructures.

If Virtual Reality is considered as an interfacing technology , it isstrictly dependant on man-machine interfacing devices (helmets,gloves, recharging devices, surveys on positioning) to sensitizecomputers to human sensations (sight, tact, aural, movement). Onesability to perceive such synthesis depends, moreover, on the ability of

ones computerized system to recreate the virtual scene, both in termsof accuracy, visible realism and movement of objects forming it. All theabove are important particularly when the user does not simply limithimself to visibly exploring the environment but interact with it too.

In an ideal Virtual Reality scenario , the user should be able to seethrough a stereoscopic display (in order to perceive the tri-dimensionality of the scene) having all displayed at bearings 180horizontally, 80 vertically . The user should also be able to feel theweight of the objects and the resistance they produce as he/sheinteracts through natural movements. However, despite the effort to

produce Virtual Reality products, technological requirements have notas yet been satisfied by the devices being used at present. The mostrealistic interfacing for both vision and tactile interaction areexcessively costly and difficult to use. Those which are user-friendlylack in realism, severely limiting ones senses during the virtualexperience.

Human Tactile Sensing System

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Determining specifications of the tactile presentation device requiresan investigation of the human tactile sensing system. A cross sectionof human glabrous skin is shown in Figure 1. As is shown in Figure 1,the skin is composed of epidermis; dermis and hypodermis Human

tactile receptors (called mechanoreceptors in neurophysiology) arelocated in the dermis and near boundaries between the dermis and theother layers. Meissners corpuscles, Pacinian corpuscles, Merkel cell-related endings and Ruffini corpuscles are the mechanoreceptors anddistributing over the entire skin. For example, the distance betweentwo Meissners corpuscles is about 600 m. Mechanoreceptive unitswhich play a role as the human tactile sensing system consists of themechanoreceptors, nerve fibers transmitting signals and nerve cellsprocessing the signals. So far, the mechanoreceptive units havebeen investigated using two kinds of experiments . One ismicroneurography , which examines a reaction to a given stimulus

using a tungsten microelectrode inserted into nerve fibers. The other ispsychophsics , which examines a human subjects replies to questionsregarding the strength of stimulus. As s result of these experiments,there are Fast adapting type I unit (FA I), Fast adapting type II unit (FAII), slowly adapting type I (SA I) unit and slowly adapting type II unit(SA II) in the human tactile sensing system. It was found thatmechanoreceptors of FA I, FA II, SA I and SA II were Meissnerscorpuscles, Pacinian corpuscles, Merkel cell-related endings and Ruffinicorpuscles, respectively.

Masahiro OHKA,Shizuoka Institute of Science and Technology,

Toyosawa 2200-2, Fukuroi 437-8555, JAPANTel: +81-538-45-0111, Fax: +81-538-45-0110, [email protected]

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Recognition of fine surface roughness is fulfilled by the aforementionedFA I . The roughness height caught by SA I is from several m toabout 100 m . SA I excites against the roughness height exceedingseveral hundred m. Amplitude below 1 m is perceived by FA II onlyif the stimulus is provided as mechanical vibration. The authors

assume SA II perceives shearing force applied to the skin surface butthis estimation requires further experimental studies to be curried out.

Characteristics of Immersive VR

the unique characteristics of immersive virtual reality can besummarized as follows:

Head-referenced viewing provides a natural interface for thenavigation in three-dimensional space and allows for look-around, walk-around, and fly-through capabilities in virtual

environments. Stereoscopic viewing enhances the perception of depth and the

sense of space. The virtual world is presented in full scale and relates properly to

the human size. Realistic interactions with virtual objects via data glove and

similar devices allow for manipulation, operation, and control of virtual worlds.

The convincing illusion of being fully immersed in an artificialworld can be enhanced by auditory, haptic, and other non-visualtechnologies.

Head-Mounted Display (HMD)

The head-mounted display (HMD) was the first device providing itswearer with an immersive experience. Evans and Sutherlanddemonstrated a head-mounted stereo display already in 1965. It tookmore then 20 years of Research to introduce a commercially availableHMD, the famous "Eye Phone" system (1989).

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A head-mounted display (HMD):

A typical HMD houses two miniature display screens and an opticalsystem that channels the images from the screens to the eyes,thereby, presenting a stereo view of a virtual world. A motion tracker

continuously measures the position and orientation of the user's headand allows the image generating computer to adjust the scenerepresentation to the current view. As a result, the viewer can lookaround and walk through the surrounding virtual environment.

To overcome the often uncomfortable intrusiveness of a head-mounteddisplay, alternative concepts (e.g., BOOM and CAVE) for immersiveviewing of virtual environments were developed.

BOOM The BOOM (Binocular Omni-Orientation Monitor) is a head-coupled

stereoscopic display device. Screens and optical system are housed ina box that is attached to a multi-link arm. The user looks into the boxthrough two holes, sees the virtual world, and can guide the box to anyposition within the operational volume of the device. Head tracking isaccomplished via sensors in the links of the arm that holds the box.

The BOOM, a head-coupled display device:

CAVE

The CAVE (Cave Automatic Virtual Environment) was developed at theUniversity of Illinois at Chicago and provides the illusion of immersion

by projecting stereo images on the walls and floor of a room-sizedcube. Several persons wearing lightweight stereo glasses can enterand walk freely inside the CAVE. Head tracking systems continuouslyadjust the stereo projection to the current position of the leadingviewer.

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CAVE system (schematic principle):

Input Devices and other Sensual Technologies

a variety of input devices like data gloves, joysticks, and hand-heldwands allow the user to navigate through a virtual environment and to

interact with virtual objects. Directional sound, tactile and forcefeedback devices, voice recognition and other technologies are beingemployed to enrich the immersive experience and to create more"sensualized" interfaces.

Moving the steering wheelA data glove allows for interactions with the virtual world:

Non-immersive VR

Today, the term 'Virtual Reality' is also used for applications that are

not fully immersive. The boundaries are becoming blurred, but allvariations of VR will be important in the future. This includes mouse-controlled navigation through a three-dimensional environment on agraphics monitor, stereo viewing from the monitor via stereo glasses,stereo projection systems, and others. Apple's QuickTime VR , forexample, uses photographs for the modeling of three-dimensionalworlds and provides pseudo look-around and walk-trough capabilitieson a graphics monitor.

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Prophecy

Shared Virtual Environments

In the example illustrated below, three networked users at differentlocations (anywhere in the world) meet in the same virtual world byusing a BOOM device, a CAVE system, and a Head-Mounted Display,respectively. All users see the same virtual environment from theirrespective points of view. Each user is presented as a virtual human(avatar) to the other participants. The users can see each other,communicated with each other, and interact with the virtual world as ateam.

As a first step in this investigation, our goal is to build a supportinfrastructure that will allow many users to participate in a shared,interactive 3D world. Such interaction will include the ability to seeeach other, talk to each other, visit locales with each other and workwith each other. The proposed system has elements of a computer-supported cooperative work (CSCW) environment, a virtual realitysystem and an online chat forum. They refer to their work as adistributed, shared virtual environment, or VE for short.

A naive and basic infrastructure for a shared 3D world is simple; itconsists of a database of objects that exist in the world, a set of toolsto populate that database and a set of devices that display thecontents of the database. The display device doubles as an inputdevice and allows users to navigate through the world and to interactwith other users and objects in the world. To achieve this, it requiressome form of communication that will allow the display devices toaccess the database and to propagate user input to the database.

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Since one of our main goals is to support a shared world, one of thekey differences between our work and existing 3D platforms is thateach user is represented in the 3D world and each user sees arepresentation of all other users in the world (commonly referred to anas Avatar ). In a system that scales to many hundreds of users,

supporting each user as a dynamic entity that roams the 3D world is asignificant technical challenge.

The simple architecture shown in Fig.1 would be sufficient to support alimited number of users operating in a low latency communicationsenvironment. Since we wish to support hundreds of users operating ina range of networking environments our goal is to understand how toscale this architecture.

Scaling issues

We face two significant problems when scaling this model. The first isconcerned with distributed consistency and the second withcommunication latency.

Figure 2: A simple architecture

Consistency

The fundamental model presented by the Virtual Society (VS) platformis one of a shared 3D space. Such a space, because it is shared, mustbe seen consistently by all users of that space. In a strict interpretationany actions that occur in the shared space must be propagated to all

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participants in that space. Further we require that conflicts betweenuser actions are either avoided, or resolved. Lastly, it is required thatactions in the space maintain their causal relationship so that a usercan make sense of a 'happened before' and 'happens after'relationship. These requirements mirror our experiences in everyday

life and are essential to any system that attempts to provide a degreeof virtual reality.

A simple example serves to illustrate these points. Consider a virtualshop with two customers (A and B) who are physically at home, one in

Tokyo and one in Hong Kong. When A enters the shop that B is alreadyin, then B needs to see A and A needs to see B. If A is holding andexamining an article, then it is required that B is not able to take thatarticle from A (conflict) or that a copy of the article is made availablefor B to examine (conflict resolution). Lastly if A then shows B thearticle and asks for B's opinion, it is necessary that the request for an

opinion arrives after A has shown B the article. Otherwise B will beasked for an opinion on an article that (s)he has never seen!

In the ensuing sections we will discuss how this strict interpretationmay be relaxed in some circumstances, and how we can exploit this.

Latency

In the simple architecture depicted in Fig.2, issues of event orderingand object locking would be resolved internally in the single database.However, if we wish to scale this system across many sites, then we

are forced to distribute the database across the sites and to ensurethat events that update the database at one site are propagated to allother sites. The need to distribute the database is primarily driven bythe communication latency in a wide area network like the internet.Since we are supporting a user based system, we are constrained byuser expectations. It has been shown that a delay in the `action-result'cycle of more than 250msec will deter users from using the system. Asone of our goals is to support a shared 3D space in the internetenvironment and since, in the current internet, delays within Japanfrequently exceed this time, we are forced to distribute state to begeographically co-resident with users and so reduce access times.

Database partitioning through Aura's

In a system such as DIVE the underlying platform maintainsconsistency at the granularity of a 'world' which encompasses manyobjects and captures a self-contained visual scenario such as a city orshop. In many cases, particularly those worlds that represent a largespatial area, such as a city, it is not necessary for a participant in one

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location to be consistent with another participant 4 (virtual) blocksaway. In that case, maintaining consistency at such a large granularityforces a high degree of false sharing.

Rather than sharing all elements of a shared world, we reduce the

sharing to a subset of spatially local objects by using an aura to specifythe spatial area of interest around a user. This spatial notion isobviously a facet of the spatial nature of a shared 3D environment andhas little parallels in a strict data application.

To reduce sharing we partition the shared world according to an aura .An aura is a notion that has evolved out of work in the area of computer-supported co-operative work and defines a sphere of interestassociated with a user. In this previous work, auras have been used asa spatial notion to support interaction models, we have adapted theiruse to one whose main purpose is to define the degree of sharing and

where necessary to reduce sharing so as to reduce participants in anyconsistency algorithm.

Objects in our system exist in a virtual world. Each world defines avirtual space captured using a 3D co-ordinate system. Each objectspecifies a dynamic aura that represents the portion of the virtualspace in which it is interested. A separate unit, an Aura Manager(AM) constantly monitors objects as they move around the sharedworld and informs objects when other objects collide with their aura.

Figure 3: The abstract architecture

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In figure 3, we can see a simple system with three user objects andtwo scenery objects. Object 1 and object two are in each other's aurasand so have a communications link between them.

In essence, we use the notion of aura to partition the database, and

the Aura Manager to track the database partitions.In our current model, we use auras as a means to control spatialinteraction. However, an aura can be concerned not simply with spacebut also with aural or sensory interaction. Thus a user may have alarge visual aura but a small auditory aura. In addition, the aura maybe dynamic. For example, when a user enters a crowded room, then itis likely that (s)he would wish to reduce his/her visual aura to cut downon the amount of information (s)he needs to be concerned with.

This is a human model of aura use but directly translatable to our

system. For engineering reasons, as a user enters a crowded locale, wewish to reduce the the degree of interaction to minimize the amount of consistency that must be supported. Hence our system willdynamically reduce the size of a user's aura depending on the numberof participants in the aura group. This approach allows us to ensurethat we never have consistency groups containing may hundreds of users, even though a particular world will be supporting hundreds of users.

Once two objects are within each other's aura, we fall back on thesecond part of our hybrid approach. Objects in each other's auras will

wish to support a degree of consistency so that they share a view of the world. Since we are now forced to deal with the issue of consistency, we need a model that allows us to apply one of a range of consistency protocols dependent upon the hardware, application anduser constraints. Before we discuss the support for consistency we willintroduce the framework in which we implement the consistency. Thisframework is based on a set of replicas which we use as part of oursolution to the latency problem.

Latency hiding

The second major problem we face when building a shared virtualworld is the ability to ensure that interactions work in real time. By thiswe mean that our maximum communication time is bounded by a userperceived notion of interaction delay. The user may initiate an event,such as selecting an object in a scene, and expects the effect of thataction to be visible within a bounded time.

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We have already started to address this problem with our use of auras,i.e. since we have reduced the participants that must take part in anydata update we have reduced the time needed to reach consensus onthe consistent state. However, this is not enough, since we have still tomake remote requests to access state. When dealing with data we can

usefully class it into three major categories; Static data . This is data which is read only and is never changed. Dynamic data whose current value may be 'out of date'. This

type of data changes over time, but it is acceptable for accessesto this data to return old values.

Dynamic data that must always be 'up to date'. Accesses to thistype of data must always return the most recently updatedvalue.

In a shared 3D space there are many data values and many actions in

the shared world that are read only or require only a delayedconsistency. For example, querying the owner of an object does notrequire shared consistency, or, changing the color of an object may notrequire that the change is immediately visible to all participants.

Languages

VRML

Most exciting is the ongoing development of VRML (Virtual RealityModeling Language) on the World Wide Web. In addition to HTML(HyperText Markup Language), that has become a standard authoringtool for the creation of home pages, VRML provides three-dimensionalworlds with integrated hyperlinks on the Web. Home pages becomehome spaces. The viewing of VRML models via a VRML plug-in for Webbrowsers is usually done on a graphics monitor under mouse-controland, therefore, not fully immersive. However, the syntax and datastructure of VRML provide an excellent tool for the modeling of three-dimensional worlds that are functional and interactive and that can,ultimately, be transferred into fully immersive viewing systems. Thecurrent version VRML 2.0 has become an international ISO/IEC

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standard under the name VRML97 .

Rendering of Escher's Penrose Staircase

Creating a 3D VR scenario involves a great number of complexcalculations. There are currently two categories of software to producethese 3D VR scenarios: toolkits and authoring systems.

Toolkits are libraries containing functions mainly for C/C++.Programmers can use these libraries to code VR applications. Thesesystems tend to to run faster, depending on the skills of theprogrammer of course!

Authoring systems on the other hand are independent applicationsallowing the user to create 3D environments. These systems do notrequire as much coding as the toolkits do, and as a result will not runquite as fast as the toolkit systems can muster.

To hold the illusion of reality, virtual reality application are extremelyresource hungry and there are very few machines that have theresources necessary to create and maintain this illusion. Even if themachine halts for a split second, the user will lose his/her sense of illusion. It may take another ten or twenty years some say beforeaffordable systems will hit the market.

Current stipulation

We have built a demonstration platform running in a Unix/Ethernetenvironment to explore these ideas. This work is derived from the DIVEdistributed virtual environment platform. Based on this work we havebegun development of a new platform more suited to an environmentwhere connectivity spans low bandwidth telephone lines, LANS and thewide area internet.

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At this stage we only have a minimal platform running as a researchprototype. This system consists of a PC based clients which are ableto visualize a scene based on the VRML scene description language.Clients communicate with local database servers using an in-houseprotocol, VSCP (very short area communication protocol), that is

optimized for geometric transformations. We currently have a simpledistributed server that supports a limited number of users andimplements the basic ideas discussed above.

Our consistency support is based upon the SID (Server IntegratedDatabase) multicast package from the Swedish Institute of ComputerScience which is also used in the DIVE system. We support the 3 basicconsistency classes and have a provisional implementation of theweaker consistency model.

Conclusion and future plans

Building a scalable distributed shared virtual environment is atechnical challenge. Masahiro OHKA has adopted a hybrid approachwhereby to use a spatial notion of Aura to reduce the degree of sharing, and then provide multiple consistency mechanisms to reducecommunication overhead. They have augmented this with replicamodels which provide client side caching for latency hiding. We believethat these combinations of techniques will allow us to support ascalable platform.

Their current a future plans are concerned mainly with extending theirinitial prototype. Our first goal is to better explore the cost of consistency in a wide area network and to adapt their class hierarchyaccordingly.

In the future they will concentrate their efforts on exploring thepossibilities of a broadband network and will port the platform toBROADBAND network which incorporates a video on demand systemand specialized display devices which are part of an associated projectbuilding a BROADBAND based set top box. A novel feature of this workis their use of the Apertos, distributed object oriented operatingsystem. This system that is based on a reflective meta-object modeloffers a high degree of system adaptability which we hope to use tofurther explore the issue of adaptive consistency.

Applications

As the technologies of virtual reality evolve; the applications of VRbecome literally unlimited. It is assumed that VR will reshape the

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interface between people and information technology by offering newways for the communication of information, the visualization of processes, and the creative expression of ideas.

Note that a virtual environment can represent any three-dimensional

world that is either real or abstract. This includes real systems likebuildings, landscapes, underwater shipwrecks, spacecrafts,archaeological excavation sites, human anatomy, sculptures, crimescene reconstructions, solar systems, and so on. Of special interest isthe visual and sensual representation of abstract systems likemagnetic fields, turbulent flow structures, molecular models,mathematical systems, auditorium acoustics, stock market behavior,population densities, information flows, and any other conceivablesystem including artistic and creative work of abstract nature. Thesevirtual worlds can be animated, interactive, shared, and can exposebehavior and functionality

Useful applications of VR include training in a variety of areas (military,medical, equipment operation, etc.), education, design evaluation(virtual prototyping), architectural walk-through, human factors andergonomic studies, simulation of assembly sequences andmaintenance tasks, assistance for the handicapped, study andtreatment of phobias (e.g., fear of height), entertainment, and muchmore.

KEY WORDS

... (VRML) (Virtual Reality Modeling Language)VRML is a 3d scene description language being standardized forscene description the World Wide Web.

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DIVE (Distributed Virtual Environment)We are currently working with the DIVE group to implementsome of our ideas within the framework of DIVE 3.0

Gibson Matrix

It is a 3D virtual world or the cyberspacePHANToM

Commercial tactile presentation systems

BOOM (Binocular Omni-Orientation Monitor) The BOOM (Binocular Omni-Orientation Monitor is a head-coupled stereoscopic display device. Screens and optical systemare housed in a box that is attached to a multi-link arm.

CAVE (Cave Automatic Virtual Environment)Developed at the University of Illinois at Chicago and provides

the illusion of immersion by projecting stereo images on thewalls and floor of a room-sized cube

CSCWComputer-supported cooperative work

VSCP (very short area communication protocol)An in-house protocol optimized for geometric transformations

References Sir, I referred to many Papers over the Internet which were referred to the following

areas. So I can conclude that my paper is referred to the following references

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Useful Web Sites

1. The Center for Virtual Environments at The University of Salfordhttp://www.nicve.salford.ac.uk/

2. Museum of Science and Industry In Manchester http://www.msim.org.uk/

3. Euravia Engineering and Supply Co. Ltd.http://www.euravia.co.uk/ 4. Fakespace Systems ImmersaDesk R2

http://www.fakespacesystems.com/ 5. Stereographics Corporation CrystalEyes Shutter Glasses

http://www.stereographics.com/ 6. Silicon Graphics Inc.

http://www.sgi.com/

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artificial reality

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