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consists of the modules DILAS Server, DILAS Manager,
DILAS 3D Modeler and DILAS Scene Generator (Nebiker,
2002b).
3.3.1 DILAS Modules
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Figure 1: DILAS System Architecture
The Server and Manager modules make up the core
components of the system. They address the aspects of storage
management, 3D scene management and querying,
representation mapping as well as 3D scene export and import.
The 3D Modeler component is built into MicroStation V8 CAD
of Bentley Systems. The 3D Modeler module performs the
mapping between the DILAS 3D object model and the
MicroStation V8 geometry model. Through the MicroStation
Java API DILAS 3D Modeler has full access to the CAD
geometry model and to the abundance of construction and
import/export functionality available within MicroStation V8.
Currently, DILAS 3D Modeler incorporates functionality for
the editing of 3D objects, the automatic generation of 3D
buildings from roof models or 2D map data and for the
interactive texturing of 3D objects.
The DILAS Scene Generator plays a key role in enabling the
web-based visualisation of very large landscape and city
models using GEONOVA's high-performance 3D visualisation
software G-VISTA. DILAS Scene Generator generates web-
based multi-gigabyte 3D scenes with large numbers of 3D
objects.
33.2 The Integration of 2D and 3D — One of the key
factors in making 3D city models and landscape models a
technical and commercial success will be the integration of 3D
landscape management solutions with existing 2D GIS
environments.
In DILAS this 3D-2D integration is achieved by adapting the
OGC Simple Feature data model and by extending it with the
spatial data types listed in the previous section. This approach
yields a number of benefits:
* the vast amounts of existing 2D geodata can also be
accessed and exploited in 3D
* the 3D geometry, for example, can be treated as a spatial
attribute of a conventional 'GIS feature'
* the 2D representation of a 3D object is visible as a read-
only attribute in any OGC SF compliant GIS
3.4 Support for Visualisation and Animation in DILAS
In addition to the broad range of 'standard' GIS functionality,
DILAS also provides a number of features, which specifically
support or facilitate the visualisation and animation of reality-
based 3D models. DILAS provides a comprehensive support for
3D object appearance, including colour, transparency and
object textures (Wüst, 2002). These appearance attributes can
be assigned to any geometric element within the 3D geometry
model. All appearance information is stored within the Oracle
9i database.
3.4.4 Texture Editor — DILAS incorporates a tool for the
assignment and editing of object textures (Figure 2). After
selecting one or several 3D objects from the database, images
can interactively be assigned to the object geometry. It is also
possible to assign textures semi-automatically to the object
geometry. First it is necessary to convert the image orientation
parameters in an XML-based orientation file. After that the
XML file can be imported in the texture editor tool. Then the
images can automatically be assigned to the object geometry.
The assigned imagery is subsequently stored in the database as
part of the 3D object model. The texturing process is supported
by additional tools for the verification and correction of normal
vectors and by an integrated 3D viewer which enables the
immediate verification of the texturing results.
*y Texture Editing - DILAS 3D MODELER
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Figure 2: DILAS 3D Modeler — Texture Editor
The semi-automatic texturing tool was developed in a diploma
thesis at FHBB (Knabl, 2003). To test this texturing tool a 3D
model of the chapel of Zwingen (Switzerland) was used. The
constructed CAD model (Figure 3) consists of about 1800
geometry elements. For the texturing approximately 300
elements were used. The integrated support for semi-automatic
texturing is an essential tool in the process of texturing complex
objects.
Figure 3: CAD model and fully textured
3D model of the chapel of Zwingen
