Interactive, Real Time, 3D Modeling
 First of all, what is a model? A model can be a 3 dimensional representation of
objects and environments that actually exist or once existed, 3 dimensional fictional objects located in a
purely imagined space, or a 3 dimensional geometric representation of volumetric
data. We will focus on the first two.
What does it mean to say that a model is real time and
interactive? Once created, interactive, real time models can be rendered and
projected on the fly, according to decisions made by users as they navigate or
fly through the model. Motion and
orientation can be continually recalculated and rendered as the user manipulates
a navigational device in concert with navigational software to change
speed, direction and viewpoint. In addition to motion, discrete objects,
animations, effects, sounds and sound effects may be initiated by the virtual location of the user, or by use of certain keys. All of this is intended to occur
with smooth continuous motion, seamless presentation and with as much detail and
realism as is appropriate and possible.
Interactive, real time modeling and navigation is not
animation. Navigating in the 3 dimensional space of the models is based on
decisions made by the user in the immediate present, and is not a series of
prerecorded images. Interactive navigation can change on the spur of the
moment resulting in unique flight paths, while prerecorded images cannot. Animated movies or sequences
rely on series of images any one of which can take seconds, minutes, hours or
days to render. These rendered images illustrate a preordained flight path, speed and direction
that cannot really be changed according the the wishes of a viewer or navigator.
At the very best a movie can be played in reverse, or at varying speeds. Interactive, real time
presentations on the other hand rely on a model database which is
constantly being referenced and are designed to display images at a rate
greater than 24 frames per second.
Model Building
In order to function in most interactive, real time display
systems a model must be composed of polygons whether it is an architectural model,
a terrain model or a scientific visualization model. At this time the
preferred application at the 3D Modeling Lab for polygon construction is Multigen's
Creator. Creator makes possible various economies, hierarchies, attributes
and processes specific to real time, interactive modeling that are simply not
found in other applications. Polygonal models can be built using other
applications such as FormZ, Maya, or 3D Studio Max, but they should be converted
and imported into Creator for finishing.
Creator is not used to build models based on scientific
data or scientific visualization models. For assistance with creating scientific visualization models go to
Scientific Visualization page under
Research Activities or contact ?RnD?.
Model Displaying
It is important to understand that the applications
that build the models are not the same ones that display them it in an
interactive, real time, virtual reality environment.  The modeling process
does not stop with the modeling applications themselves, it continues on into
the applications that support the display and navigation. It is in the
display and navigation process that the unique features of real time,
interactive models are made evident and it is here that the setup and
configuration are edited. At the UCLA Visualization Portal the primary
display and navigation application is vrNav which is built upon the Performer
and vrJuggler Application Programming Interfaces(APIs). Multigen's Creator
and other modeling applications produce Openflight files(.flt) files which vrNav can load, along with all of their instructions and
file references. VrNav is under continual development at ATS and is
available for free download at
Download vrNav.
Interactive, real time models can be displayed in the
ATS Visualization
Portal(virtual reality theater), on Lab workstations, on laptops, or on specially outfitted
portable "shuttles" or computers.
Models can be projected in the Portal and in like facilities, according to a
variety of display formats, including flat plane stereo, flat plane,
spherical stereo and spherical. Each one of these formats provides
for a distinctly different viewing experience, and each one has it’s own
distinctive advantages and disadvantages. Facsimiles of these models, including
movies, animations, web VR objects and images can also be produced and
displayed in their respective venues such as CD's, videos, websites and print. The support provided by ATS extends
well beyond the planning and creation of projects, it also involves their
promotion and dissemination. |
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