A GENERAL FRAMEWORK FOR REPLICATED EXPERIMENTS

IN VIRTUAL 3D ENVIRONMENTS

D. Biella and W. Luther

Institute of Informatics and Cognitive Sciences,University of Duisburg-Essen, Lotharstr. 65, Duisburg, Germany

Keywords: Modelling of virtual 3D environments, reuse of parameterizable framework, automated code generation.

Abstract: This paper reports on a parameterizable 3D framework that provides 3D content developers with an initial

spatial starting configuration, metaphorical connectors for accessing exhibits or interactive 3D learning ob-

jects or experiments, and other optional 3D extensions, such as a multimedia room, a gallery, username

identification tools and an avatar selection room. The framework is implemented in X3D and uses a Web-

based content management system. It has been successfully used for an interactive virtual museum for key

historical experiments and in two additional interactive e-learning implementations: an African arts museum

and a virtual science centre. It can be shown that, by reusing the framework, the production costs for the lat-

ter two implementations can be significantly reduced and content designers can focus on developing educa-

tional content instead of producing cost-intensive out-of-focus 3D objects.

1 INTRODUCTION

Web-based 3D applications are very popular in the

learning, commercial and entertainment sector. De-

spite the success of these products, the cost of de-

signing and producing content-rich 3D learning en-

vironments is still a major issue, especially if realis-

tic models, non-deterministic simulations and spe-

cial user interaction are required.

Our work focuses on the production of learning

content with a high degree of interactivity, photo-

realism, reversibility and non-deterministic simula-

tion models, which allows learners to understand the

design and methodology of an experiment through

an individualized, interactive, Web-based applica-

tion (Biella and Luther, 2007).

In a recent interdisciplinary project concerned

with the historical replication of interactive key

experiments in psychology and education, 2D and

3D implementations of B.F. Skinner’s historical

experiment on operant conditioning were imple-

mented, tested and evaluated by students (Biella,

2006). Results showed that

o the 3D version effected a higher degree of

spatial and cognitive immersion,

o the 3D visualization of the experimental

setup was more realistic in terms of graphi-

cal quality,

o users tend to accept mixed (2D and 3D) con-

tent despite media discontinuities in favor of

knowledge creation,

o the experiment was easier to comprehend in

3D.

The question of whether to use 3D or 2D depends on

the design requirements, the target user group and

the model data to be presented. Design considera-

tions are listed in the section “Modelling pipeline”

and discussed in the section “Discussion”.

This paper reports on a parameterizable 3D

framework for Web-based experiments and identi-

fies reusability options.

It highlights three case studies that prove the fea-

sibility of the concept and its cost efficiency, and

gives an overview of recent work to enhance the

framework.

2 MODELLING PIPELINE

The modelling pipeline for replicated experiments in

virtual 3D environments presented by Biella (Biella,

2006) includes a general framework and several

workflow components that are suited for reusability

(Figure 1).

316

Biella D. and Luther W. (2008).

A GENERAL FRAMEWORK FOR REPLICATED EXPERIMENTS IN VIRTUAL 3D ENVIRONMENTS.

In Proceedings of the Fourth International Conference on Web Information Systems and Technologies, pages 316-323

DOI: 10.5220/0001519503160323

 SciTePress

Figure 1: Reusability options of the framework within the

modelling pipeline.

Initially, a real-world experiment is analyzed from

an authentic setting or from primary and/or secon-

dary sources with a focus on the 3D geometrical

model of both the experimental assets and the his-

torical surrounding, an animation model, an interac-

tion model, and an simulation model.

The input/output hardware interfaces and driv-

ers, the rendering software, the modelling languages

and tools, and, optionally, a framework development

for the integration of multiple experiments are de-

termined by specifying conceptional design re-

quirements that depend on the target user group and

the complexity of the geometrical, interaction and

simulation models.

The formal model description describes the

process of defining the animation, interaction and

simulation models in abstract notions, such as

mathematical functions, statistical models or state

machines. These models are digitized by using suit-

able model description languages, such as unified

modeling language (UML). The implementation of

these models (Interaction/Simulation logic) depends

on the programming and scripting languages deter-

mined as a result of the conceptional design re-

quirements.

The following design considerations have been for-

mulated in (Biella, 2006) with regard to Web-based

museums for replicated experiments.

 Historical context representation: Although

2D visualizations may suffice for the pres-

entation of an abstract theoretical model, the

visualization of a historical laboratory envi-

ronment is challenging. In a 2D visualiza-

tion, such information has to be provided

separately through additional sources, such

as a sequence of photographs or text de-

scriptions. A 3D model allows the designer

to integrate contextual information in the

space surrounding the experimental setup.

 Impact of occluded surfaces: Surface occlu-

sion of objects with crucial functionalities

within an experimental setup can disturb the

knowledge transfer. In this case, 3D imple-

mentation must offer sufficient viewpoints

or other techniques (for example, surface

transparency).

 Implicit 3D experiments: Experiments that

involve implicit 3D setups are best suited for

implementation based on geometrical mod-

elling and free real-time user navigation.

 Model complexity: Animation, interaction

and simulation models vary in their degree

of complexity and may require high-level

programming languages instead of common

Web-based scripting languages.

 I/O Interfaces: Input/output interface re-

quirements must be defined according to

user’s perception channels.

 Data format consistency: A set of multiple

3D worlds should be implemented in a con-

sistent data format.

3D model asset acquisition describes the process of

gathering 3D raw data usually by 3D scanning or 3D

reconstruction. The post-production of 3D data im-

plies storage of high-definition 3D data in a flexible

file format (e.g.: X3D, XML), polygon and texture

size reduction and export in a Web-based data for-

mat, as defined in the conceptional design require-

ments. Both Web-compatible logic and the 3D

model represent a single replicated experiment (3D

content).

The presentation of multiple experiments re-

quires the development of a metaphorical model,

which defines a navigation scheme, spatial meta-

phors, and an exhibition layout. With regard to a

(real world) building metaphor, experiments are

connected through vertical and horizontal metaphors

that represent thematic and temporal selections of

experiments and allow the user to navigate between

them.

Cost-efficiency aspects with regard to the creation of

particular 3D exhibits suited for learning have al-

ready been presented (Biella and Luther, 2007).

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317

The virtual laboratory realization presented here

underlines the feasibility of the theoretical approach

and stipulates that the production cost of 3D content

could essentally be reduced by code reusability.

In this paper, we want to focus on reusability as-

pects of the surrounding museum framework, which

is intended to allow 3D content designers to effi-

ciently create several standard 3D museum assets, so

they can focus on actual content development, espe-

cially for Web-based learning museums and virtual

science centres. The modelling pipeline, the frame-

work and reusability options are depicted in Fig-

ure 1. They concern the spatial design, including

lighting and texturing, interaction logic, navigational

schemes and spatial or temporal metaphors.

3 THE FRAMEWORK

The framework for the replication of experiments in

virtual environments (referred to below as the Repli-

cave framework) was first developed for an interac-

tive virtual museum for key historical experiments

and is implemented in X3D and PHP (Biella, 2006).

It features both pre-defined and partly parameteriz-

able routines for the automated generation of an en-

trance hall, a gallery, a multimedia room, graphical

user interface (GUI) components and metaphor-

based connectors leading toward the laboratory

rooms in which the interactive experiments are lo-

cated.

Figure 2: Conceptional metaphor with maximal number of

laboratories (wireframe view including position descrip-

tors).

The framework references a real-world building

metaphor. Basic framework assets are visualized as

building parts at the ground-floor level. Content-

related locations can be accessed through meta-

phorical connectors (Figure 2). A connector’s X3D

code consists of static and dynamic 3D objects that

are combined into a single X3D scene graph. For the

dynamic placement of thresholds, seven positions

(N1-N3, E1, E2, W1, W2) are reserved to which

laboratory doors, a small media room door or walls

are allocated according to a certain layout matrix.

The dynamic generation of the wings is achieved by

including static X3D code fragments that define

either a wall, which renders the wing’s entrance

closed, or the full wing layout.

In analogy with the building metaphor, the tem-

poral metaphor is the vertical connector. On each

level, the doors of this allocation place form a meta-

threshold and give access to meta-paths. The desired

path and destination threshold is defined by the

user’s selection of a different content or experiment

on an appropriate navigation panel. The panel is

rendered dynamically at runtime and lists all avail-

able presents.

3.1 Entrance Hall

As the user’s initial starting point in the 3D world,

the entrance hall is an obligatory asset. By default,

the main hall is cylindrical with a transparent domed

ceiling. The design is intended to reproduce the at-

mosphere of a modern museum building located in

an urban environment, which is visualized by a blue

sky texture and externally placed building fragments

that suggest the urban context (Figure 3).

Figure 3: Entrance hall (with 3D data progress indicator).

The exit door and the thresholds leading toward the

main media room, the gallery, and the vertical con-

nector are exclusively and equidistantly connected to

the entrance hall, virtually dividing it into four quar-

ter pie sections. The reception desk, with a recep-

tionist’s avatar and a login terminal, is located in the

section between the gallery and the metaphorical

connector. Dynamically generated information pan-

els listing the available experiments are located at

the reception desk and in the elevator (Section 2.5).

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The three other sections are decorated with items

that underline the context (research-related images)

and 3D furniture objects.

The exit door is an interactive plane that allows

the user to leave the system and that can be config-

ured to initialize post-visit routines, such as opening

a new browser window for an evaluation.

3.2 Gallery

The mainstream of psychology is presented in the

gallery, which is octagonal in shape. This design

allows the installation of seven information-related

walls and an eighth wall that provides space for a

connector to the main hall. The gallery’s static 3D

model defines outer walls and a transparent roof in

accordance with the design of the main hall.

Large coloured information boards display the

various scientific research fields following the con-

tent and colour design of an optional 2D-based time-

line. 3D information plates are created by dynamic

scripts and display short informational texts (for

example, a curriculum vitae) and a photograph. Each

plate has an interactive event sensor and an individ-

ual viewpoint configuration that allow the user to

navigate there by simply clicking on them (jump

navigation). The text-based content and photographs

displayed in the gallery are stored separately from

the multimedia content of the laboratories and the

media rooms.

3.3 Multimedia Rooms

Replicave uses a two-tier approach: General multi-

media content about a given topic or person (image,

video, text) can be managed separately from the

multimedia data that describes the virtual experi-

ments. Hence, the framework contains pre-defined

designs for two multimedia room layouts: a large

central multimedia room located on the ground floor

and a small layout for topic-related content.

As a result of this approach, learners can access

all available 2D multimedia documents in the central

multimedia room, which can serve as both a library

and an appetizer for a potential 3D implementation.

Furthermore, it allows content creators to integrate

existing 2D content without the requirement of pre-

senting a 3D experiment. If at least one interactive

experiment is present, a small version of the multi-

media room is automatically generated in the 3D

content section that contains only topic-related

documents.

Both room layouts share the same functional

elements and visualization metaphors: For each

topic or person, there is a book shelf that contains

the corresponding multimedia documents repre-

sented by interactive 3D icons distinguished by their

multimedia document types—book (text based

document), film roll (video document) or picture

frame with preview (image file).

Figure 4: Central media room with dynamic 3D architec-

tural design for multimedia content visualization.

All multimedia assets can be directly administered

via a file-based document management system

(DMS). The 3D icons representing the assets are

automatically generated at run-time.

The parameterizable layout in the central multi-

media room is achieved through an automated shelf

creation, which originates in a dedicated corner of

the room and is designed as a dynamically sized

bulge. For large numbers of shelves (that is, topics

presented in the multimedia database), it extends as

a corridor of fixed width in a 45-degree angle from

the adjacent static walls. This architectural design

pattern leads to a library area with convex outer

walls, so that the shelf objects are occlusion-free for

any user located in front of them (Figure 4).

3.4 GUI Components

Replicave features the following GUI components:

 Five different 3D interactive buttons (exit, con-

text-sensitive help, information on 3D naviga-

tion, up, down);

 Single HTML capable overlaid 2D frame.

The GUI components can be reused and individually

extended in experiment-related 3D environments.

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3.5 Metaphorical Connectors

Connectors allow the user to navigate between the

entrance hall and content-related spaces as well as

between different experiments. Two connectors are

used: The vertical connector (here, an elevator) is

used to navigate between the different topics, while

the horizontal metaphor (here, a floor) is used to

navigate between different 3D experiments on the

same topic.

Dynamic content is generated in both connec-

tors. An interactive topic selection panel in the ele-

vator lets the user chose the desired content. The

horizontal connector is based on parameterizable 3D

model templates. Two templates are available: the

building floor (default) and a small-scaled simplified

model of the building floor that serves as an interac-

tive 3D map.

The default template’s shape depends on the to-

tal number of doors that are to be visualized. For a

minimal visualization, the centre of the floor, the

door leading to the small media room and one labo-

ratory door are displayed. For a complete (maximal)

layout, two side wings are added, each of which

provides access to two laboratory doors, while three

doors (a single media room door and two laboratory

doors) are visualized opposite the elevator.

3.6 Other Assets

The framework has recently been extended by an

avatar selection room metaphorically designed as a

dressing room and a parameterizable template for

experimental rooms (Hiller, 2007). Furthermore,

new X3D nodes were created to partly replace ex-

ternal scripting.

3.7 The Document Management

System

Replicave uses the open-source software Philex

(http://sourceforge.net/projects/philex/) for the file

and folder administration. It features user admini-

stration, Web-based file and folder management

with basic operations, editing of text-based files,

configurable access restriction regardless of file con-

tent and a user interface with tree-based folder visu-

alization. Due to the hierarchical folder structure and

multi-user support, content is grouped in dedicated

folders and managed via the DMS. At least five ad-

ministrator or curator roles can be deduced by set-

ting user-specific root folders. Each laboratory or

exhibition room is initially loaded by opening a

script file. Specific initialization and content files

offer a high degree of flexibility

4 IMPLEMENTATION

The Replicave framework is implemented in Exten-

sible 3D (X3D) and the PHP scripting language.

Interaction is implemented in ECMAScript. The

system requires a PHP5-capable Web server. On the

client PC, an X3D browser plug-in is required. The

framework has been successfully tested with the BS

Contact VRML/X3D plug-in by Bitmanagement

Software GmbH and Microsoft Internet Explorer 5.

The following case studies work with the BS Con-

tact VRML/X3D plugin, version 6.2 or higher, and

Microsoft Internet Explorer 7. Together with

DirectX 9.0c, the high-level shading language HLSL

is supported and was used for a soap bubble experi-

ment in a virtual science centre (Hiller, 2007).

5 CASE STUDIES

The feasibility of the concept presented here has

been tested in three case studies. While the Repli-

cave framework has been reused in two implementa-

tions, the author of the third implementation decided

to create an entirely new framework.

5.1 Virtual Science Center

The virtual science center contains several interac-

tive scientific 3D experiments that refer to various

mathematical theories. Users are expected to learn

through interaction with virtual installations.

Hiller (2007) used the Replicave framework and

showed that he could significantly reduce the pro-

duction time required for framework design and

visualization. Decorative 3D-objects, furniture and

plants were used or slightly modified for the desk,

the wardrobe and the exhibition rooms. With this

savings, resources could be spent primarily on the

production of learning content, and a total of five

new interactive 3D experiments with simulations

were developed and implemented.

First, the experiments were classified with regard

to their spatial appearance, simulation model type,

interaction logic and manipulation features. This will

enable parts of the code to be reused to implement

extensions of experiments or similar experiments,

such as the brachistochrone and tautochrone prob-

lem (Figures 5 and 6).

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Figures 5 and 6: Brachistrochrone—inverted cycloid ver-

sus a straight line with the same endpoints; tautochrone—

the ball will take a constant time to roll to the end point,

regardless of its starting position.

At first glance, visual representation of the experi-

mental environment enhanced by avatars (Figures 5

and 6) do not deliver the outcome in the form of

textual results or functional dependencies among

variables written in 2D interface elements. We invite

the user to find physical laws behind the experiment

by watching and trying out the simulation. However,

it may be worthwhile to include additional kinds of

text displays or help desks in a future version.

Figure 7: “Lights on” experiment with initial 2D instruc-

tion screen.

Figure 7 depicts the “Lights on” experiment, which

uses complex action logic. The figure shows a table

with seven small lights and individual commutators

for switching the lights on and off. However, each

switch influences not only its own lamp but also

both adjacent lights. The goal of the experiment is to

achieve a situation in which all lamps are lit with a

minimum of switching operations. This kind of ex-

periment requires a mathematical model or an im-

plemented action or interaction logic to enable the

computer to simulate a player and to find and dis-

play the correct solution. In a recent project dealing

with interactive cryptographic protocols, we devel-

oped a methodology to create a PetriStateMachine

that executes the action logic of the players involved

(Baloian et al, 2007). It was shown that Petri net

editors and simulation engines such as Renew

(available at http://www.renew.de/), support time-

efficient modeling of action and interaction logics.

5.2 African Art Museum

The Replicave framework was also successfully

used in an implementation of an African arts

(“grassland”) museum (Mafo, 2007), in which the

framework’s gallery assets were used as a primary

exhibition space (Figure 8). Changes could be lim-

ited to adapting texture image files in order to com-

ply with an appropriate design for the exhibition

context.

Existing interaction facilities allow for manipu-

lating 2D image-based content as well as 3D sculp-

tures. Information panels were updated, and simple

new signalling elements were introduced to help

users navigate within the adapted room installation.

This work could be done by any nonspecialist with-

out deep knowledge in 3D modelling languages.

Again, it has been shown that resources could be

spent on the exhibition content rather than on the

framework design surrounding it.

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Figure 8: Gallery room in the grassland museum.

5.3 Virtual Art Museum

Unlike the two aforementioned implementations, the

virtual art museum created by W. Liu (Liu, 2007)

required a specific visual and geometrical frame-

work design (Figure 9). Instead of using the Repli-

cave framework, an individual framework was de-

signed and implemented.

It could be shown that the framework-related

work took 50% of the entire content production

time, underlining the advantage of reusable frame-

work designs.

Figure 9: Sculpture room in the virtual art museum.

At the same time, the implementation suggested

possible extensions of the framework, including the

implementation of a graphical editor using drag-and-

drop mouse actions to modify the X3D content

graph on the fly, encompassing

 spatial design,

 lighting and texturing of walls and furniture,

 modification of assets.

Such a new framework can be used to create virtual

versions of existing museum installations.

6 DISCUSSION

Today, the design of virtual 3D applications is very

popular, and there is abundant literature on this

topic. However, the realization of virtual laborato-

ries and museums is long and expensive. There are

several papers (Kleinermann, 2006) that outline the

procedure to follow in the design of a VR applica-

tion and number important tools for modelling the

scene, defining the objects and means of interacting

with them. These papers provide a first impression,

whereas the inherent complexity of the creational

process makes it necessary to consult special pur-

pose literature.

In a recent paper, Hendricks et al. (2003) report

on virtual African art galleries. In a comparative

study, 2D and 3D environments were evaluated. The

results of the user study showed that users have a

clear preference for 3D environments only if they

are not too complex and provide the users with a

high level of navigational support, whereas 2D set-

tings are better suited to convey a large amount of

information that exists in sequential form.

These results encouraged us to use the Replicave

framework in the realization of the grassland mu-

seum. An initial evaluation with a small number of

participants partly confirmed observations made by

Hendricks et al. concerning interaction and 3D navi-

gation.

3D modelling languages, like X3D, use scene

graphs to build a 3D spatial design. A notion that is

key to reusing code consists in rewriting the scene

graph.

Unfortunately, changes in the scene graph in-

tended to bring about a local modification of an ob-

ject with respect to its geometric shape, texture or

position should take into account the context of the

relevant node. In Reitmayr and Schmalstieg (2005),

the authors present the idea of adding a context ele-

ment to the traversal states of a scene graph that al-

lows the scene graph to be parameterized and reused

for different purposes. An annotated context-sensi-

tive scene graph improves its own inherent flexibil-

ity when acting as a template with parameters set

during traversal of the graph. Using the new con-

cepts, a general framework called “Studierstube” is

presented, together with a dedicated model server

component containing the scene graph of the build-

ing model and an interface that allows users to inte-

grate already designed components into their own

scene graph realizations.

Automatic generation of user-specific content is

addressed in a paper by Chittaro et al. (2004) and in

further papers cited therein. The authors propose a

novel tool that provides automatic code generation

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for adding personalized guided tours to 3D virtual

environments that were developed using frameworks

able to dynamically generate X3D content.

7 CONCLUSIONS

We have presented a general framework for repli-

cated experiments in virtual 3D environments that is

parameterizable and reusable. The framework is

embedded in a new generalized modelling pipeline

that promotes cost-efficiency by reusing existing

design patterns and 3D assets.

The approach was successfully applied in two

implementations of interactive Web-based virtual

3D exhibitions: a grassland museum for African art

and a virtual science centre. In both cases, designers

were freed to focus on content development. A third

implementation illustrated the significant amount of

additional resources required for individual frame-

work design without using an existing framework

library.

8 OUTLOOK

A further extension of the number of parameteriz-

able variables and a complete conversation to XML-

based model and content description languages are

part of ongoing research. Another focus of our future

work concerns the inclusion of conversational agents

in analogy to existing solutions for real museums

(Kopp, 2007).

ACKNOWLEDGEMENTS

We thank our anonymous reviewers, whose detailed

and helpful reports have helped us to improve this

paper.

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