Civil Engineering Reference
In-Depth Information
The constantly updating augmented space displays only what is visible to a user
at a particular location. This means that there are no previously defined viewpoints
that restrict the location from where an animation can be observed. Instead, the
user can freely change position, and the view direction (i.e. head orientation), while
the position and/or orientation of the virtual contents inside the augmented space
are continually updated. The procedure of constantly adjusting the position and
orientation of the virtual objects overlaid on top of the real world is often referred to
as registration, and has been one of the major challenges overcome in this research.
To achieve precise registration of virtual objects and create augmented scenes of
simulated operations, a fully functional Global Positioning System (GPS) based
tracking mechanism has been developed. The details of this mechanism have been
described elsewhere (Behzadan
et al.
, 2008).
5.4 Technical approach to create AR animations
The application of DES tools to simulate construction processes has been widely
investigated (Tucker
et al.
, 1998; Martinez and Ioannou, 1999). DES is a powerful
objective function evaluator that is well suited for the design of construction
operations. It runs on the concept of separating activities linked together based on
their resource needs and precedence logic. DES as applied to construction opera-
tions planning and analysis entails the creation of models that represent how
construction operations will be performed. These models consider the different
resources that are required to carry out the construction operations, the rules under
which the different tasks that compose the operations are performed, the man-
agerial decisions made during the operations and the stochastic nature of events.
Once the models are created, the modeled operations can be simulated in the
computer and the statistical measures of performance for the operations can be
studied (Kamat and Martinez, 2002).
To create smooth animations from the results of a DES model, events that mark
the beginning and end of discrete activities have to be interpreted and commu-
nicated to the visualization tool in a continuous chronological order. To achieve
this objective, using an authoring language that automatically creates time stamped
events in the form of sequential statements written to an animation trace file is a
very viable approach (Kamat, 2003). The generated animation trace file can be then
fed into the visualization application to link each simulation entity to a CAD object,
and dynamically manipulate CAD objects based on the contents of the visualization
trace file.
In addition, to cause objects under the control of such simulations to be aware of,
and react to the user motions in the augmented scene, the augmented environment
implementation must communicate bi-directionally, on a continuous basis, and at
a high speed with location tracking devices. This communication is very critical in
obtaining real time position and orientation as the user walks inside the animation
to observe the scene from different perspectives. The data acquired from tracking
devices are vital parts of the application in order to display the final animated
output. Figure 5.1 shows the approach taken in the presented research to use the
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