| Ralf-Peter Mundani
| creator |
Mundani, Ralf-Peter
| | Bungartz, Hans-Joachim
| | date |
2004-07
| | | | description |
Octrees - hierarchical data structures based on recursive
substructuring - have turned out to be a powerful representative of
the hierarchical paradigm, advantageous in a large variety of
applications such as visualisation, computer graphics, databases
resp. data mining, mesh generation, numerical simulation, or
Geographic Information Systems (GIS). In this paper, octrees are
used to build up a framework for the integration of CAD, simulation,
and visualisation tasks from the field of structural engineering in
a network-based cooperative working environment. It will be shown
that, by providing octree-based tools, the coupling of these tasks
and the control of the entire design process can be improved and
simplified.
Starting from a CAD model, due to a new method based on the
intersection of half-spaces, an octree representation can be
efficiently derived, if necessary also in real time more details). A
linearisation followed by a binary encoding of such trees results in
streams that can be assigned to Boolean operators or more
sophisticated tools for further processing - even on-the-fly. As
such streams can be described by a Chomsky-II-grammar, their
integrity - e.g. after transmission over a network - can easily be
checked by a corresponding finite state automaton. Based on octree
encoded streams, tools for various purposes like providing
interfaces between different applications (e.g. CAD and numerical
simulation tasks such as computational fluid dynamics) or collision
detection between single parts of a geometric model, for instance,
are possible.
Furthermore, to ensure global consistency of shared data processed
by several experts in a network-based cooperative working
environment, for instance, a geometric model is stored in a
Relational Database Managment System (RDBMS) which can only be
accessed by an octree and corresponding check-in/check-out
functions. Thus, any modified parts intended to be written to the
RDBMS and conflicting with the rest of the data can easily be
detected. As octrees - because of their inherent hierarchy - also
allow access to the data on different resolutions levels (e.g.
walls, rooms, or floors), even conflicts among various processes can
be detected and, hence, entire design processes can be coordinated
and improved.
Another application scenario - visualisation and virtual reality -
is also covered by this framework. Here, the former discussed model
can be augmented by any arbitrary data (e.g. room informations), and
a graph for shortest-path algorithms can automatically be derived
and manipulated, meant for viewing both as VRML application within a
web browser and as immersive stereo projection on more sophisticated
devices like a power wall or a CAVE.
Summarising, the usage of an octree-based framework for the
integration of processes from the field of structural engineering
not only bridges the gap between the different applications like
CAD, simulation, and visualisation, it also simplifies and improves
the control abilities of these processes as a fundamental in a
network-based cooperative working environment.
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