World Transactions on Engineering and Technology Education  2002 UICEE
Vol.1, No.2, 2002
173
INTRODUCTION
In the last ten years, the field of Augmented Reality (AR) has
been recognised as one of the most promising areas of
computer graphics. During this time, a variety of innovative
applications have been developed, stressing the importance of
augmented reality in everyday life.
However, only a small proportion of the applications reported
in the past have been based on real time performance. Largely,
this type of deficiency derives from registration problems and a
lack of generating mobile computing power [1]. Thus,
augmented reality remains a topic of continuing research.
However, for many applications, such as cultural heritage [2],
archaeology [3], military services, architecture, entertainment
[4], and the use of cheap AR technology, it is possible to
achieve good results, as demonstrated in the authors’ system
presented below.
The main objective of augmented reality technology is to
superimpose computer-generated information directly into a
user’s sensory perception [5], rather than replacing it with a
completely synthetic environment. Augmented reality systems
can improve performance times when the training is conducted
on real objects [6]. Users within augmented reality systems
must be able to interact with the 3D information in a natural
way, like they do in the real environment. Much research is
taking place on augmented reality interfaces in order to achieve
this goal [7].
The findings presented in this paper are the outcome of an
ongoing research project called the Virtual Interactive
Teaching Environment [8]. This system was designed to enable
the educator to use more sophisticated techniques and as a
result to help the students to learn more effectively through the
use of Virtual Multimedia Content (VMC).
The contribution of this current interactive system takes into
consideration both technological and educational issues.
Consequently, a multimedia augmented reality interface was
designed and implemented in an effective and efficient manner
for both teachers and students.
RELATED WORK
The work presented in this article relates to and incorporates
elements from different research areas: augmented reality user
interfaces and virtual training.
The authors’ notion of the interactive system dubbed
Multimedia Augmented Reality Interface for E-Learning
(MARIE) is closely related to MagicBook, a powerful
augmented reality interface [9]. This system uses a real book to
transfer users from reality to virtuality. Virtual objects are
superimposed on the pages of the book and users can interact
with the augmented scene. Another similar augmented reality
generic platform for location supports direct interaction with
virtual objects using a pen and a pad interface [10].
From an educational perspective, a summary of the potential
benefits for the use of existing virtual environments in
education and training are well defined elsewhere [11]. In
addition, Computer-Aided Learning (CAL) has played an
important role in engineering education and training [12].
A good educational augmented reality learning system for
mathematics and geometry education is based on the
Construct3D tool, where teacher and students can interact
through various interactive scenarios [13]. The MARIE system
mixes together virtual reality techniques and computer human
interaction techniques [14]. Finally, The classroom of the
future is an interesting augmented reality approach to improve
education [15].
Multimedia Augmented Reality Interface for E-learning (MARIE)
Fotis Liarokapis, Panos Petridis, Paul F. Lister & Martin White
University of Sussex
Brighton, England, United Kingdom
ABSTRACT: An interactive Multimedia Augmented Reality Interface for E-Learning (MARIE) is presented in the article. Its
application for engineering education is discussed in order to enhance traditional teaching and learning methods; however, it is
equally applicable to other areas. The authors have developed and implemented a user-friendly interface to experimentally explore
the potential of augmented reality by superimposing Virtual Multimedia Content (VMC) information in an Augmented Reality (AR)
tabletop environment, such as a student desk workspace. The user can interact with the VMC, which is composed of threedimensional
objects, images, animations, text (ASCII or three-dimensional) and sound. To prove the feasibility of the system only a
small part of the teaching material was digitised and some experimental results are presented in the article.
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OVERALL ARCHITECTURE
The architecture of the MARIE system prototype is presented
in Figure 1. It consists of a lightweight Head Mounted Display
(HMD), a small camera and a computer. The system uses
some of the functionality of the ARToolkit, a free distributed
software C library that was designed to easily develop
Augmented Reality applications [16]. This toolkit makes use of
computer vision techniques to effectively compute the real
camera position and orientation relative to predefined marked
cards.
Figure 1: Examples of trained markers.
The general pipeline of the video see-through system can
be explained through the following scenario. The user is
equipped with a custom built see-through HMD, which is a
CyVisor with a bullet camera mounted. The user observes a
tabletop indoor environment (ie a typical student desk
workspace). The user places a set of predefined markers on
the table according to some predetermined learning context
and, as the user looks at the markers through the HMD,
multimedia information is mixed with the real environment in
real time.
DESIGN OF THE SYSTEM
One of the main goals of this system was to design a
lightweight system that can be easily used by inexperienced
students. Hence, large and cumbersome HMDs are not used;
instead, this project implemented the HMD from existing
technology such as the CyVisor and simple bullet cameras.
Other off-the-shelf hardware and software components were
also utilised in order to keep the total budget low and also to
create an ergonomic architecture that is easily reusable.
The software adopted for three-dimensional modelling is
3ds max (version 4.2). Three-dimensional sound is created
using a software interface to audio hardware, called
OpenAL API [17]. A Pentium III processor at 700 MHz
was used and a G-force IIII card as the graphics card. When
the system runs at maximum resolution (768×576 pixels)
then the frame rate efficiency is reduced. Therefore, a
lower resolution (384×288 pixels) was used in order to
achieve real time performance. Thus, the CyVisor with
800x600 pixel resolution is more than adequate. It should also
be noted that the visualisation can also be viewed on a standard
monitor.
The teaching material is decomposed into appropriate units
(future work will see these units specified in XML) and a
marker was created for each one. Therefore, the users have a
selection of markers associated with the teaching material (see
Figure 1). The teacher now has only to devise the learning
strategy. That is, the sequence in which they instruct the
students to observe the markers and hence display the learning
material in an AR environment, (similar to the MagicBook
concept).
Real World
Augmented World Register and
render 3D objects
Decompose video
into frames
Detect and calculate marker
position and orientation
Video camera
mounted on
HMD
PC
Figure 2: Architecture of the system.
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With teacher guidance, the student thus selects the specific
marker needed for the required visualisation. As an example, a
3D representation of the Moore machine flow chart has been
generated by analysing the teaching material (lecture notes).
To derive the animation, the scene is rendered and exported to
a predefined file format (ie moore.avi). The decoder used to
compress the file was divx™ (a digital video compression
technology based on the ISO MPEG-4 standard). In this way
broadband performance was provided that is significantly
superior to competitive technologies.
IMPLEMENTATION RESULTS
When the user’s view detects a marker, then the camera’s
output provides input into the video capture subsystem (a
winTV card), where VMC is overlaid onto the video in real
time (see Figure 3). The resulting augmented visualisation
generates output to the HMD and monitor as shown in Figures
4 and 5.
Figure 3: MARIE’s operation.
The main window represents the augmented world, where the
three-dimensional objects are superimposed on the tabletop
environment in real time. Three-dimensional text is also
overlaid on the window acting as a help option for the user. The
bottom left window plays an animation describing the object
and the theory. The bottom right window displays images
representing two-dimensional diagrams.
In essence, MARIE augments all the required multimedia
information to the users. These windows can be swapped
around and can be displayed in separate windows if required.
USER-TEACHER INTERACTION
Users and teachers can interact with the augmented reality
interface in two different ways. The users can freely manipulate
the marker in three-dimensional space to receive a different
perception. They can also use the mouse to zoom, pan
and rotate the rendered images and animations. They can
also select to play the .wav file associated with the
marker using a keyboard button. On the other hand, the teacher
(who does not wear an HMD) can interact with the student
using the mouse or the keyboard, again in the same way.
One clear advantage of MARIE is that the teacher can speak
to the student at the same time that the user listens to the
.wav file and the system then mixes the two sound sources
together.
Figure 4: Monitor augmented reality view.
Figure 5: Interaction with the system.
Finally, non-immersed users (those who do not wear HMDs)
can collaborate with the immersed user through the monitor and
voice (see Figure 5). Imagine the scenario where the teacher
advises the immersed user in the same augmented workspace.
CONCLUSION AND FUTURE WORK
MARIE is focused on enhancing the teaching and learning
process in an augmented reality e-learning environment. The
main advantage of the presented augmented reality system is
the low cost and real-time augmented presentation. While the
system presented here is applied to engineering education, it is
a generic platform applicable to a variety of other teaching and
learning augmented reality environments, such as cultural
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heritage, archaeology, surgery operations, military services,
architecture and others.
Future work will involve the improvement of human computer
interaction techniques and the addition of other useful haptic
devices to track objects in the AR scene, allow navigation and
so on. The implications of such an augmented reality system
could include other forms of augmentation like touch and smell.
Indeed, all of the senses may be mixed with the real
environment through state of the art hardware equipment.
ACKNOWLEDGEMENTS
Part of this research was funded by the EU IST Framework V
programme, Key Action III-Multimedia Content and Tools,
Augmented Representation of Cultural Objects (ARCO) project
IST-2000-28366.
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