Game Development Reference
In-Depth Information
Geometric models of virtual
environments
Guillaume Moreau
14.1 INTRODUCTION
In a virtual environment, the observer moves in a world which is a representation of a
part of the reality or of an imaginary environment (Fuchs, 1996). In most of the cases,
the representation given to the observer is primarily visual. This visual representation
is formed by projecting a 3D geometric model of the virtual environment on one or
more flat 2D images using virtual cameras whose movements can be linked to the
observer's movements.
This environment of course does not have only geometric elements. Let's take
the example of a virtual city. A virtual city is made up of at least one representation
of buildings and road networks as well as the factors moving in this city (see fig-
ure 14.1 representing a simulation of a tramway at a crossroad in Nantes (Donikian
et al., 1998)). The geometric representations of the buildings and the road network are
insufficient for this simulation (Donikian, 1997). The simple integration of a tramway
in the scope of this study made it necessary to not only create a geometric and kinematic
model of a tramway, but also to define the behaviour of the driver-tramway pair while
crossing certain noticeable elements on the roads (signals, intersections, tram stops).
Figure 14.1 Impact study on the integration of a tramway at a crossroad in Nantes. (Illustration:
IRISA/Siames, with permission)
 
 
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