sistemas 3d multiusuario _ingles_ julio-30-03

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VIRTUAL RECREATION OF REAL 3D SPACES THROUGH INTERNET USING SHOCKWAVE TECHNOLOGY

Abstract

Internet is mainly a communication system in continuous evolution, wich provides us allthe means for the propagation at world level of susceptible contents of being digitalizables,

as well as the combination of different communicative systems.

Making use of that powerful quality and taking as development base the Shockwavetechnology of Macromedia's. We have developed an engine that integrates real time 3Dtechnology environments, a multiuser system and also access to integrated databases. Totest the engine, we have recreated a historical environment; the Square of the Quintanalocated in the old town of the city of Santiago of Compostela. The environment is integratedin a web page, accessible by a web browser.

1. Introduction

Communication systems have been developing in a vertiginous way. From the

employment of writing to television, cinema or telephone. But all this has been small in frontof the integration of all these technologies in a new one called Internet that adds newinteractivite degrees. The subjectis not just a espectator like with TV but rather he canrequest information and interactivate with it. The combination of these different ways allowsus to create more efficient and accessible talkative systems, making the access toinformation and the interaction more simple and attractive . Internet also provides us all theways for the propagation of contents at world level, and simplifies the access to all kind of multimedia information like text, sound, video or other stuff able to be digitizeable.

Each comunication system condition, in a specific way, our senses, determining ourperceptive outline. So in virtual representation of real spaces what is done is to show arecreation of what surrounds us, through a visitor's immersion in a synthetic reality. Thevirtual representation of real environments by infographic system in real time, facilitates theidentification, and the approach of new realities and visions to users of any part of the world,

as well as transmiting a spacial reference of our environment.

From the mid-nineties there have been multiple intents of generalizing the 3D environmentsfor personal computers. Regrettably these efforts have met with two big restrictions: theslowness of the CPUs and the small band width in the case of the systems distributed byInternet.

These limitations have been palliating by means of the generalization of connections of wideband as are the cable and the ADSL among the users of Internet, as well as the enormousdepreciation of the graphic 3D cards and their wide diffusion among domestic equipment,being nowadays a standard element of their configuration. To this it is necessary to add theenormous improvement experienced in the last years by the development environments of 3D and web, as is the employment of SDS (Subdivision Surfaces) [1], Streaming or vectorial

[3] animations. Therefore the improvement of the transfer speeds in Internet and the powerin the hardware allows to bring near the users nearer to the 3D technology.

An 3D environment is not simply a static image; it is a complex and dynamic environmentthat has to be controlled by the user, which supposes an important problem of accessibility[14]. Contrary to the 2D environments, in which a remarkable standardizationhas been developed in its interactibilidad, by means of a series of visual elements as arebuttons, lists or text squares among others. Regarding 3D this process has still not takenplace. We don't have interactive references that can take as standard, for that reason itsupposes a challenge for the designer to facilitate the accessibility and to minimize thelearning time.

When we speak of environments in the first person we have to identify three elements

fundamentally: the character, the environment and the interactivity.Being the character the user's virtual reference in the environment, their interactive tool,with which the virtual environment can travel.




It is only not about maximizing the visual quality of the environment and of the character if this has a physical representation, one also has to maximize the satisfaction gained by thevisit simplifying the communication between the character and the environment, by meansof an appropriate planning and use of the interactibility.

In that line, at the moment we do not have left another alternative that to torture the user, beingcaused who accede to the surroundings via keyboard and mouse, that evidently distan much of legs, hands and head. That takes us to the necessity fundamentally to take care of a limitedresource, which there is to take care of, at the time of developing for Web, and is the patience.Taking it always like reference, if we want at least that our surroundings are used by people,and referenciando it by means of the following relation.

Patience>=download time+periodo de aprendizaje del entorno

And with these antecedents we came to the creation of three-dimensional virtual surroundingsthat fundamentally were easily accessible stops most of users and connected systems toInternet.

2. Considerations of the audience

Our objective public are all those users of Internet, with some basic knowledge of the useof visual operating systems, and interest in the knowledge of historical places.

We compare this group of users with the nearest group from a technical point of view to ourenvironment that are the users of 3D games[4][11], fundamentally in PC systems. And wereached the following conclusion. The users of our 3D environment in general have lesstechnical knowledge and patience than the average PC players. They don't worry aboutquestions like the time of answer of the ping, drivers or hardware configuration. If somethingdoesn't work they simply don´t use it, while a user accustomed to use 3D games for PC will

look for the form of configuring their system to obtain a good operation of the environment.This forces to automate in the end the technical configuration of the environment and tominimize the technical prerequisites, as well as to give multiple alternative preconfigured.

3. The tool: Shockwave

Around the summer of 2001 Macromedia[8] I launched into the market in collaborationwith Intel an upgrade of their software of development Managing multimedia. The new 8.5version supposed a substantial change since it introduced as main novelty a complete motor3D[5][6], as well as a powerful programming language called Lingo 3D[2]. This new capacitycan be used as much for the generation of local environments as for their distribution

through Internet by means of the use of the Shockwave plugin.

This new version of the tool provides us with a higly programmable and modern 3Ddevelopment environment that is joined to those already supported characteristics of theDirector; a complete 2D motor, a stable plugin that allows us the distribution of ourdevelopments through Internet and the MUS (Multiuser Server) [7] that allows theinteraction of multiple users (50 in their free version and up to 3000 in the registeredversion) that is provided for nothing by Macromedia.

Reaching this point we must ask ourselves the following question. How does this differ towhat has been done for more than 4 years with other technologies.If the 3D environment is substituted by VRML[15] whose development license is free and

easy to develop, the multiuser system by java or ActiveX and the database by active pages(ASP, PHP,…) or simply by a handful of you pages in HTML, we would already have all of that.




So we outline the main differences between the use of Shockwave and other suitablevariants previously indicated:

1.Size: At the moment this is the fundamental premise to keep in mind when developingenvironments for web. Elevated sizes of the files limit the accessibility to the same ones.And that is surely the main limitation of the VRML when being generalized in Internet.Since in its different versions, either in ASCII or compiled the size of the VRMLenvironments is very high. A technology that seeks to be transmitted through the currentnet cannot have superior weight of 2Mb for small virtual recreation (without including thetextures). With Shockwave the same environment can end up weighing 15% of its VRMLequivalent.

2.Hardware: Another defect of the VRML, is that to renderize small areas (320x240px)it requires a high calculation of the CPU. Mainly from the graphic card. As well assubstantial quantities from the RAM memory. With Shockwave very superior results canbe obtained in bigger renderized areas (800x600), with a very inferior consumption of resources.

3.Integration and simplification: Working with Shockwave, we can embrace thedifferent necessities of our system with the same tool. Everything is reproduce with thesame plugin and it is programmed with the same language (Lingo). we can make forexample, any event that takes place in the 3D environment to cause an action in the 2Dsystem or MUS and vice versa. This means a substantial simplification as opposed to theVRML that needs of other different technologies to obtain the same functionalities.

4.Streaming: we can develop not only an algorithm action for when the system istotally discharged, but rather we can go on offering the functionality of the system withonly one part of the environment loaded. We can also find the support of SDS on thepart of the 3D motor. Which allows us to work with a mesh in low resolution and to go onadding to it the rest of the poligonity as this is being unloaded.

5.Plugin: This is the black point shared by both technologies. To be able to be executedin a navigator web they need the previous installation of the corresponding plugin that inboth cases exceeds three mega bytes. Although it is necessary to differ that theShockwave, besides the rendered 3D technology includes a complete 2D motor.With regard to the diffusion of the same, the plugin Shockwave is one of the mostextended by Internet, more than 367 million users have installed this plugin. Also theaccess to the same, is simple (it is carried out through Macromedia) and free or charge.While the VRML plugin is not standardized, it is generally complicated to get and not allits versions are free or charge.

All these results were obtained by means of the test of different 3D models, recreated somuch in vrml as in Sockwave technology. Using in both cases IE5 web browser, andShockwave plugin for the reproduction of the Shockwave surroundings, and the Cosmo

Player[16] for the reproduction of surroundings vrml.

Illustration 1. Making a shockwave file




4. The system

Starting from the biggest communication system created up until now, we raise two basic

objectives: the verisimilitude and the accessibility. So, on the one hand it was aboutdeveloping a system that allows us to provide the user access to an 3D environment as realas possible. And on the other limiting as much as possible the requirements of hardware asof software so as to have access to the environment. In that sense, the fact that the systemis based on an available plugin as much for Windows as for Mac, and is reproduced on astandard navigator, gives us access to most of our objective public. On the side of thehardware, although not necessary (if advisable) an accelerating 3D card, and that thesystem allows a substantial adaptability to the client machine (LOD (Level of Detail), SDS oroptional mipmapping among other elements) it allowed access to the environment in anacceptable way, to teams with speeds of 200MHz and 64Mb RAM (this it is the most basicsystem in which the environment was tried out).

In the first phase of the development of the prototype, the user enters the environment in

first person and travels through it via keyboard or by means of pressing some displacementbuttons. With the left button of the mouse it can pulse on the different points elements of the localization so that the system provides him with information on the same. It can alsocommunicate with the different users that are in that same localization via chat, previousregistration and selection of climatological conditions in that moment.

In a second phase the user is represented by an Avatar(the user's virtual representation inthe environment) and it can select up to a maximum of four users that can integratethemselves in his same instance of the environment with his corresponding Avatars. Thisrestriction is not applied to the quantity of users that are in the chat. The quantity of simultaneous Avatars is limited in the same environment for two reasons; to optimize theyield of the system, it is of no use it we introduce dozens of Avatars if to change theenvironment is later innavegable because client schemes it on the other hand the able to

move the environment efficiently, and itdoesn't make any sense to go to the recreation of ahistorical place and not be able to do anything because it is saturated with Avatars thathinder our vision of the environment.

The freedom of movements is absolute, one is able to go up stairways, enter buildings orlook in any direction.

The environment includes different climatological conditions as are sun, rain and snow. Aswell as different time zones going from day to night in function of the real hour of therecreated localization. The system checks the hour of the user and after carrying out theprecise adjustments it modifies the illumination of the environment dynamically.

It also possesses a series of climatological effects as are fog or the movement of the clouds.

The sound of the environment is positional and it is distributed by both loud-speakers of theclient's equipment in function of the user's orientation with regard to the origin of the sound.Locutions of some points of information and access to different areas are also included.

4.1 The architecture

This system is based on the architecture client-servant. The servant has to store the dcrfiles, the HTML pages he has to have in use the servant MUS (Multiuser Server).




Illustration 2. Diagram of the relation client-server

4.1.1 Graphic interface

The advantage in use the same technology for all the surroundings is that it allows us to create

clean and integrated graphical surroundings. We reserved the bottom part to the multiuser system and to provide the information of the surroundings and to help in the displacement.Whereas the top part is occupied in its totality by the 3D surroundings.

Illustration 3. Snapshot of the envioroment.

4.1.2 Virtual environmentWe take as a physical reference an incomparable environment as is the old town of Santiagoof Compostela and inside it we center ourselves in the recreation of the Quintana Square.Enclosure also called Square of theDead, next to the cathedral of Santiago of Compostela. Itwas been created using CAD/CAM an digital photography.

We opt mainly for this localization for three reasons:

1.Easily accessible as much to take space references as to photograph it digitally, for a latertexturization.2.Its two levels separated by some stairways that cross the entirety of the square allow usthe inclusion of multilevel displacement.

3.The documentation of its different elements that constitute it is easily accessible.




Illustration 4. Diagram of access and visualization of the envioroment information

4.1.3 The database

The database is generated in XML (Expandable Markup Language) [12], later on by using of an XSL insole (Expandable Style Language) [13] we transform it into an array that is passedas a parameter to one of the properties of the object in charge of the administration of thedatabase.There are two charts one that includes the name of all the models that have associate

information and a reference to the point of related information. In the second chart they aredefined all the data of this points of information, as for exemple the name, description orconstruction. Working with two charts facilitates us to link several objects to the same pointof information or to improve at any moment statements fields.The reason of including the database inside the file is not only for one reason. Mainly we optfor this solution because the follows:1.Limit the use of a servant of active pages: We liberate the servant of having toprocess the petitions of information of the different sensitive elements of the environment.Since when being included in the own file this process is carried out by the client machine. Atthe same time we don't need to have to install a database agent in the servant to providethis service.2.Compress: The direct access to the the databese in XML would imply to have to dischargea file of about 100K, because the XML comes in format ASCII without any compression type.While when going included in the file Shockwave it is compiled inside the same one beingreduced at about 10K.

Ilustración 5. Database convertion

4.1.4 Multiuser The part multiuser part is elaborated by using MUS (Macromedia Shockwave MultiuserServer) [7] that allows us until a max. of 1000 people communicating simultaneously bymeans of:

• A chat that allows a conversation in real time.• A shared presentation, allowing the presenter and the audience to see a presentation

at the same time.• To execute a multiuser interactive game.• To maintain a conversation conversate online with a shared board in where each user

could write.

This communication can be carried out in three ways:• Sending the petitions to the MUS and those being forwarded them to the other

movies.• By the establishment of communications peer-to-peer directly with other movies.

• With a connection based on text, as it can be a standard mail or a servant IRC.




Illustration 6. Diagram of comunication client-server

The MUS has been used mainly because its power, its absolute integration with theShockwave technology because its access via Lingo that is the same programming languageused in the development of the prototype.It has been used for the chat integrated in the shockwave movie, accessing to it by of aprevious registration of the user's name and having access to different chat sessionsdepending on the virtual space in which was in in that moment the visitor. In this case thesession was only one because it had only one spacial reference.In a second phase not implemented, by the moment, the MUS will be the one to synchonizethe movements of the physical representations (Avatars) of the different users, in theirrespective places of the environment.

4.1.5 Avatars (Virtual Representations of the users)

The physical representation of the user in the virtual surroundings is made through a model3D of a person. This representation is denominate Avatar.

The inclusion of Avatars allows a fast approache of the user to the 3D surroundings bymeans of a visual reference of its virtual presence in the surroundings through a personageand at the same time it gives an important space reference, since it allows to determine thedimensions of the surroundings recreated through a human reference.

The Avatars are modeled with the applications of Mayan design 3D 3DSMax4 and 3,5following the following process:

1. The model wireframe is generated in low poligonity.2. The model is textured.3. The avatars bones are created, wich allow to animate it later.4. The animation of the avatar are aplied to him, using movement capture’s libaries,

that provide an enormous realism.

The user could select between different personages and sexes. Once it’s selected someelements can be chose as they are the face, clothes and height. Each have differentmovements allowing them to move, to surpass obstacles, to salute or to yawn among others.




Ilustration 7. Avatar in front Holy Door

5. HardwareThe fundamental guideline in the development of the application was to optimize the

accessibility to the same one. Reason why it has always been to minimize the necessaryhardware requirements to reproduce the environment.

The development was made in a AMD k6III-400MHz, 128Mb ram, graphical card TNT232Mb and Windows 2000 professional. Being later tested in the equipment indicated in Table1. Equipment used in the initial test of the prototype, evaluating as much the speed andpossible errors in the reproduction of it.

Hardware SO/Software Rendimiento

PIII 600Mhz, 256MB RAM, graphic cardTNT2 32MB with 3D support

Windows 2000IE 5, DirectX 7, OpenGL1.0

Optimal*

PII 200MHz, 64MRAM, graphic card4MB without 3D support

Windows 98 1EdIE5

Slow***

PIII 500Mhz, 256MB RAM, graphic card8Mb with 3D support

Windows 98 2EdNS6, DirectX 5

Optimal*

AMD K6-III, 256MB RAM graphic cardGeFore2MX 32MB with 3D support

Windows XP Home EditionIE 6, DirectX 8, OpenGL1.0

Optimal*

G4 300Mhz, 128MB RAM, graphic card16RAM with 3D support

OS.9 y OS.XIE5, OpenGL1.0

Medium**

Table 1. Equipment used in the initial test of the protype

* Fast 3D navigation, access to the information. ** Medium speed of 3d navegation, and fast access to the information. *** Slow speed of 3d navegation, and fast access to the information.

It is necessary to say that even if Shockwave technology includes a render by software forthe 3D surroundings, is important the use of Directx 5+ or OpenGL1.0+ for an optimalvisualization of the system.




6. Testing the system

In the search of the optimization of the prototype, the test of the application by people whodo not have a high knowledge of navigation by surroundings 3D to be able to fit thecapability of use and accessibility of the system, at the same time that we can fix all bugsderived from the development.

In the test three parameters were evaluated:

1. Accessibility: One was to measure the degree of difficulty in the use of the Interface,navigation by the 3D envioroment and access to the information:

2.Improvements and modifications: It was required to them to sailed by thesurroundings and gave ther opinion about all dificulties found, what they missed inthere and what they would eliminate. It is necessary to distinguish two differentgroups of person in the test. One supervised directly and the other doing the testprivately, acceding to the demo via Web. In the first case it allowed us to see the user

behaviour, showing us what they did at the first time to acced to the envioronment,what did not use or problems they found with. In the second case the obtained results,served to us mainly to evaluate possible errors in the system and to have opinions of people from other countries.

3. Errors: We checked the different errors that could arise as much in the own prototypeas in their visualization in different navigators and operating systems.

The test was made by a population of 41 people and as it is indicated in the following tables.

Country Testers

Spain 29USA 4

UK 3Argentina 2Checoslovaquia 1Australia 1Brasil 1

Table 2. Geographic distribution

Level Testers

High 15Medium 6Low 20

Table 3. Previous knowledge of use of 3D envioroment

S.O ComputersWindows 2000 profesional 29Windows XP 6Windows 98 SE2 4Mac OS 9 1Mac OS X 1

Tabla 4. Distribución por sistemas operativos

The main reached conclusions were:

• Accessibility: The impossibility of the users to approximated themselves in extremisto the elements of the envioroment1,simplify navigation enormously, mainly forthose ones more inexperienced.

1 We used systems of collisions based on the use of of ray tracing, that aside from reducing to the consumption of resources on the part of the equipment client, us permitio the establishment of a seguiridad area, that impede that the




In order to evaluate the time of necessary learning for the handling of thesurroundings, we divided two periods:

1.The time that takes the user to begin to move himself by the surroundings (toadvance, to raise stairs, to rotate) and to accede to the information.

2.The time that takes to him in acceding to actions more avanced, as they are tolook around in all the directions or to accede to the multiuser system.

The results in both cases were very satisfactory, as much those less advanced tookabout 20 seg. in moving through the square and 1 min. in familiarized themselveswith the movement and the access to the information. Feeling in general morecomfortable using the keyboard that pressing the visual cursors of the surroundingswith the mouse.The second phase did not exceed in any case more than 1.30 min., not even with thelower users. In certain cases the users did not perceive the existence of the chat,although where there were informative panels on the same one, when the

envioroment starts, and that occupy a substantial part of the inferior panel.

• Improvements and modifications: All the testers made reference to the smalldimensions of the envioroment (the prototype recreated just a square not alowing toaccede to the rest of the city).Some users missed people walking by the square (the ups and downs were notincluding in the test version). And some of the lower experienced users asked for theimposibility to see the people who were walking by the square. In that line there wasa pair of tests in which where included in demo the projection, in a screen integratedin the surroundings 3D, the realtime images coming from one webcam located in thissquare. But that peculiarly disturbed to the low and average users, who seemed tobe in front of the mirror of Alicia, which made us choose to pospone the definitiveinclusion of that option.

• Errors: Was a failure in the reproduction of the surroundings in OsX, but finally itwas due to an error of plugin that was solved later by Macromedia.

7. Future implementations

Within the new implementations for this system we distinguished, between improvements of the own motor and the different uses that can be done with it. As an improvement tried agreater monotorización of the users is tried, doing that the pulsations on the differentelements from the surroundings, will be stored in a data base lodged in the servant who laterwill provide statistics to us, thus to know the elements that more interest wake up in the

objective public. To optimize the load in streaming of the other locations in the city, todiminish the died times of the user while these elements unload. Also we are working in theinclusion of lightmaps and dynamic textures, particle systems sensible to the yield of sorrounding, and other improvements of the own 3D engine.As future applications, the possibilities are enormous, but among them the lines of development fundamentally focus in the recreation of devices and machineries, as much aspotential surroundings as they can be future buildings or facilities. Which offers us theopportunity to make them accessible to an ample objective public, and to study the answerand behavior of it before that future reality. And in addition the direct application to anothertype to locations as they can be museums or public buildings among others.

user patch to the walls of the surroundings or any other was had left obstaculo. This avoids the lost one of visualreference of the surrounding elements, and reduces the possibility that substantially the navigator feels lost.




8. Conclusions

To end this article and summarize of it, it is possible to say that to the use of 3Dtechnologies for the recreation and transmission through Internet of historical realities,completely increases the approach to the users of the network, as well as the level of identification and use of the same one. These technologies allow us to easily generatecontents easily distributed through Internet, at the same time that we obtain a ratioquality/accesibility/time of development very satisfactory.

In this prototype we already generate a easily navigable and a high interactivity degree 3Dsystem. Simplifying the access to users who, because of their little knowledge or ability withthese surroundings, had limited themselves to the traditional web page with photos and text.And also it is necessary to add the big inprovent due to the minimization of the physical sizeof the file like and the technical requirement to use it. Which has resulted positively in thelevel of accessibility to this tecnology.The future of the tourist communication, and recreations of spaces in the presentglobalization occurs through this kind of solutions, been or not this technology their short or

half term route.

9. References

[1] Director 8.5: Shockwave Studio para 3D. Phil Gross y Mike Gross. Ed. Anaya Multimedia.Febrero 2002

[2] Director’s third Dimension. Fundamentals of 3D programming in Director 8.5. PaulCatanese. ED. Que. Octubre 2001

[3] Vector Math for 3D Computer Graphics. Central Connecticut State University, ComputerScience Department. chortle.ccsu.ctstateu.edu/

[4] Real-Time Interactive 3D Games. Allen Partridge. Ed. Sams. Noviembre 2001

[5] What's New in Director Shockwave Studio. Jay Armstrong, Greg Barnett, StephanieGowin, Tom Higgins, Marcelle Taylor y Frank Welsch. Ed. Macromedia. Marzo 2001

[6] Using Director 8.5 Shockwave Studio. Jay Armstrong, Barbara Herbert and StephanieGowin. Ed. Macromedia. Marzo 2001

[7] Usign the Shockwave Multiuser Server and Xtra. Jay Armstrong, Greg Barnett, StephanieGowin, Tom Higgins, Marcelle Taylor y Frank Welsch.Ed. Macromedia. Marzo 2001

[8] Macromedia. www.macromedia.com

[9] Character Animation for Shockwave3D. Mark McCoy.www.macromedia.com/desdev/articles/char_anim.html

[10] Building character. Toby Gard. www.gamasutra.com/features/20000720/gard_01.htm

[11] Developing online console games. Peter Isensee y Steve Ganem. www.gamasutra.com/features/20030328/isensee_01.shtml

[12] Extensible Markup Language (XML). www.w3.org/XML/

[13] The Extensible Stylesheet Language (XSL). www.w3.org/Style/XSL/

[14] Web Accessibility Initiative (WAI). www.w3.org/WAI

[15] VRML97 Specification. web3d.org/fs_specifications.htm

[16] Cosmo Software. www.cai.com/cosmo/

sistemas 3d multiusuario _ingles_ julio-30-03

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