CIPA 2003 XIX th International Symposium, 30 September - 04 October, 2003, Antalya, Turkey
purpose of a map is to be an abstraction of reality; so the output
of 3D GIS that can be both interactive and animated maps. The
conventional 2D maps output by conventional GISs adequately
represent functional data, but cannot represent visual data well
at all. On the other hand, 3D maps do an excellent job of
representing visual data and are also capable of handling
functional data. The coupling of 3D GIS with interactive and
animated output can only serve to further a map’s ability to
accurately depict geographic data. Current forms of output for
2D maps from GISs are many and include bitmap, pict, gif, and
pdf formats. With the recent prominence of the World Wide
Web as a medium for information exchange, gif and pdf
formats, with cross platform compatibility, are particularly
attractive. An attractive format is “Virtual Reality Modeling
Language” (VRML) for distributing 3D GIS output. VRML 2.0
allows fully immersive environments, interactivity and real-time
animation capabilities. VRML browsers work as plug-ins for
common Web browsers and are currently available for most
platforms.
In this paper an introduction to the 3D internet modeling
language VRML\GeoVRML is provided and its usefulness to
GIS people is explored. 3D modeling of geographic scenes
presents opportunities of scientific exploration and visualization
that are not possible in 2D. This paper shows how to create
three-dimensional visualizations using commonly available and
inexpensive tools. Objects can be queried and modified by the
user and linked to underlying data, providing a GIS-like
environment in three dimensions. The efforts at producing 3D
visualizations of the cemetery, the fortresses and the
surrounding areas focused on intensely to research, design and
build a generic virtual environment and to describe 3D spatial
representation of the historical objects with respect to the each
other using VRML as a modeling language for the exploration
the historical background of living on that historical site.
Here, it is showed how to combine GIS-Visualization
integration efforts with recent VRML work. The development
of VRML models will allow users to interact with three-
dimensional models via the World Wide Web. For these efforts,
this means that users with a VRML browser will be able to
interact with three-dimensional displays of spatial and terrain
data sets.
. 3. METHODOLOGY
An application with interactive interface over the internet is
introduced in this research to manipulate the historical
information, recreate and visualize the fortresses and the
cemetery. The application consists of three modules, the first for
displaying a historical object by using virtual reality concept.
The user accessed with WWW browser and walked around the
historical place in the virtual environment. The second module
is a geographical information system, which was applied to
manipulate historical information. These two modules can be
worked in the Internet and linked together with hyperlinks and
JavaScript, Personal Home Page (PHP) in the WWW system.
The last module applied the object-oriented virtual reality has
just begun to develop. The security restriction is provided in the
system, which allows only authorized person to manipulate
databases and virtual reality information on internet.
VRML was chosen as a means of visualizing in 3D because it
offers a platform and software independent file format. Its
flexibility, ease of transfer and for the viewing options it allows
users are the other specifications to select in 3D applications.
Developed scripts provide that the user can easily interact with
the 3D model, predefined walking or flying around and through
it. It is also the chosen 3D format for the Web. There are many
VRML browsers that can be used to view and interact with the
model; although there is considerable variation in how well they
render the models. The language, however, has the potential to
describe the behavior of objects, provide links to other
documents on the Web, represent interrelations that can be used
to retrieve and visualize 3D spatial information and thus serve
as an interface to 3D GIS. (VRML Consortium)
VRML files may contain references to files in many other
standard formats. JPEG, PNG, GIF, and MPEG files may be
used as texture maps on objects. WAV and MIDI files may be
used to specify sound that is emitted in the world. Files
containing Java or JavaScript code may be referenced and used
to implement programmed behavior for the objects in your
worlds. Script nodes can be inserted between event generators
(typically sensor nodes) and event receivers. Scripts allow the
world creator to define arbitrary behaviors, defined in any
supported scripting language. The VRML 2.0 specification
defines Script node bindings for the Java and JavaScript
languages.
Aside from interactively positioning point of view, VRML
allows the user to interact with 3D objects in a 3D world. The
linkage (hyperlink) functionality has added to 3D model in
VRML to enable the project members and users to retrieve the
data regarding the historical object. The query capabilities on a
3D map about attribute data have been added the model. A
standard web browser equipped with any one of many freely
available “plug-ins” can become an interface into a three
dimensional virtual reality. The best part is that high-quality
VRML browsers are publicly available for free and work with
high-quality web browsers that are also publicly available for
free. (The Annotated VRML97 Reference)
A preliminary “Virtual Interface” has been developed using
PHP, Java and JavaScript to interact with VRML worlds. The
interface provides two-way communication between the user
and the VR terrain, not only extracting positional information
from the model but also allowing the user to move between
viewpoints and select the view required. This preliminary
interface has purposely not been embedded within the VR space
to emphasize the 2 dimensional links to the 3D environment,
much as would be expected in using maps in the real world.
VRML also allows 'Script nodes' by which the developer can
add external programs (typically written in Java or Javascript)
to extend its functionality.
VRML worlds are primarily defined by nodes that describe
shapes, interpolators, sensors and scripts, linked by routes
which pass messages between nodes. Most nodes are of
predefined structure containing fields and events that describe
their appearance and behavior; however the node set may be
extended by use of prototypes and scripts. The VRML Script
node provides a general purpose node for programming new
sensors and interpolators for VRML whereby appearance and
behavior of objects in the scene may be modified and defined.
Script nodes contain references to the appropriate Java .class
file to call when the script is initialized. The ‘Virtual Interface’
application opens via a ‘ProximitySensor IsActive’ field when
the VRML file is launched. The script node enables events and
nodes to be passed from VRML to Java (Eventln), commands to
be sent from Java to VRML (EventOut) and the definition of
fields in the VRML file to be used in the Java program. (The
Annotated VRML97 Reference) Events, (such as
