Fabule - A Multi-Purpose Animation System for Simulation and Virtual
Reality
by Mathieu Desbrun, Jean-Dominique Gascuel, Marie-Paule Cani-Gascuel
and Nicolas Tsingos
Physically-based animation systems
are now capable of simulating a vast range of phenomena, by modeling rigid
bodies or viscous liquids in dynamic environments. At iMAGIS, a joint project
of INRIA, CNRS, Joseph Fourier University and the Institut National Polytechnique
of Grenoble, we have developed a flexible animation system called 'Fabule'.
The aim is to provide a useful modeling and animation platform for simulation,
virtual reality and production of animation films. At the same time, our
flexible and adaptive system enables us to easily implement and add new
modules, facilitating state-of-the-art research in various fields such
as interactive modeling, deformable models, or sound rendering.
Animation and simulation research has given rise to a large variety
of animated models, providing efficient tools for both simulations and
virtual reality. The main difficulty is to offer a unified system that
combines standard animation techniques, such as keyframing or rigid body
collision handling, and recent developments such as virtual reality techniques.
To avoid stilted (or rigid) features and take advantage of re-usability,
we have developed Fabule, a flexible programming system along with interfaces
and common tools which allows us to build a global and coherent set of
various animation techniques. This system was developed focusing on three
different topics: modeling with implicit surfaces, fast simulation of deformable
materials, and sound rendering.
Modeling is the ineluctable first step of any animation. To define the
shape of an object to animate, standard techniques make use of parametric
patches to model the surface. A new approach has been introduced recently
that characterizes an object by giving an equation satisfied by the surface.
While having a surface defined implicitly may seem inappropriate, this
formulation provides several advantages over parametric surfaces: complex
topology objects, with holes and branchings, are handled easily with implicit
surfaces; the interior of the object is in addition intrinsicly defined
by an equation, which favourably contrasts with conventional boundary representations
where computationally expensive tests are needed to determine whether or
not a point is in the interior of an object. Fabule offers interactive
and intuitive modeling using implicit surfaces (see Figures (a) and (b)).
Deformable models have also been explored extensively at iMAGIS. As
implicit formulation of objects allows significant gain in computation
time, Fabule provides an efficient and interactive animation platform where
objects from elastic to quasi-liquid can be used (see Figures (a) to (c)).
The novelty is that our implicit coating can treat precise contact modeling
with high quality rendering. Recent developments include space-time adaptive
models where resolution is automatically adapted by locally refining or
simplifying the sampling according to motion. This principle allows us
to concentrate computation where needed, resulting in optimized implementations,
which is still rare in animation.
The last avenue explored is the simulation of sound. With the development
of virtual reality, soundtrack generation is becoming an important issue
in Computer Graphics. Producing convincing soundtracks involves the rendering
of sound interactions with the dynamic environment: in particular sound
reflection and absorption due to partial occlusions or Doppler effect are
fundamental to realism. Fabule enables us to generate realtime soundtracks
of simple animations without any post-production, or can simulate sound
rendering of a given environment.
These three aspects, altogether with additional optimized techniques
such as articulated structure animation (see Figure (d)), result in a multi-purpose
state-of-the-art animation system. A C++ implementation with open hierarchies
of modules also makes Fabule a test-bed for research in Computer Animation.
Object-oriented support for programming and available tools shorten dramatically
the implementation of new research.
Figures a-e: Snapshots from various animations created with Fabule.
iMAGIS collaborates with the BRGM in Marseille in order to build a geophysical
tool for natural risks prediction of rock falls from cliffs. With an approximated
set of values characterizing the soil and the vegetation type, several
simulations are performed with different initial conditions that help the
delimitation of hazard areas (see Figure (e)). An other collaboration is
currently active on teleconferencing and virtual reality with the CNET.
We also have active contacts with the CSTB of Grenoble for simulation of
acoustic rooms and sound rendering, and are involved in the Platform for
Animation and Virtual Reality European TMR network. Future activities include
further developments of virtual reality techniques.
Further information can be found at: http://www-imagis.imag.fr/FABULE/fabule.html
Please contact:
Jean-Dominique Gascuel or Marie-Paule Cani-Gascuel iMAGIS
Tel: +33 4 76 63 56 85
E-mail: Jean-Dominique.Gascuel@imag.fr,
Marie-Paule.Gascuel@imag.fr
