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Photo 2 - The Puma robot drawing a centaur in space
with a lamp.
Laurentiz (dead in 1991), an animation with
satellite images using Vivaldi’s concert. As
opposed to the previous proposal, we intend to use
the information from the satellite images to
generate the music also, exploring natural
phenomenons such as vortex, snow and wind, falling
waters and fire [Sims, 1990], suggesting the
movement and the music. Thus, musical parameters
such as velocity, intensity, duration and timbre
will be extracted from the images’ information and
used for the definition of the various states of a
sound context that will be articulated as a result
of the images’ trajectories. The pixels of the
satellite images will be seen as particles in a
system [Reeves].
3.1 Particle Systems
A particle system is a collection of many minute
particles that together represent a fuzzy object.
Over a period of time, particles are generated into
a system, move and change from within the system,
and die from the system [Reeves, 83].
To compute each frame in a motion sequence, the
following sequence of steps is performed: (1) new
particles are generated into the system, (2) each
new particle is assigned its individual attributes,
(3) any particles that have existed within the
system past their prescribed lifetime are
extinguished, (4) the remainding particles are moved
and transformed according to their dynamic
attributes, and finally an image of the living
particles is rendered in a frame buffer. The
particle system can be programmed to execute any set
of intructions at each step. Because it is
procedural, this approach can incorporate any
computational model that describes the appearance or
dynamics of the object. For example, the motions and
transformations of particles could be tied to the
solution of a system of partial differential
equations, or particle attributes could be assigned
on the basis of statistical mechanics.
Particle systems provide for the creation of complex
structure and motion from a relatively brief
abstract description. They can be used to produce
dynamic and "fuzzy" effects that are difficult to
achieve with traditional objects made of surfaces
and animated with non-procedural motion. They have
previously been used to model fire in the Genesis
Effect of Star Trek II, tree and grass, breaking
waves, fireworks and other abstract effects.
We have a particle system being developed at
Fundaçäo CTI that works with magnetic fields. We
253
Will also supply several levels of operations along
the spectrum between detailed kinematic control and
physically based simulation. The goal is not to
strictly obey physics and reality, but to suggest a
variety of effects easily created. Physical
simulations can create motion in a much more
complex and realistic looking than motion achieved
by moving objects along spline curves or through
keyframes. Objects animated kinematically often are
not perceived as dynamically correct, whereas
objects animated by true physical simulation will
look correct.
3.2 Operations with Particles
Operations used to move particles are divided into
four categories: those that set the position, those
that set the velocity, those that alter the position
or "apply" a velocity, and those that alter the
velocity or apply an acceleration. In addition to
position and velocity particles have state variables
that are used by some animation operations but not
by others. For example: type, age, mass,
spiral-axis, color, opacity and size can be used.
Other spare slots exist for information such as
initial velocity, a color to fade to, or an age to
die at. A valuable component of a particle animation
system is a particle preview capability.
3.3 The Animation.
The animation will be obtained from the movement of
pixels which will be colored using information from
the different satellite bands. The trajectory will
be associated to algorithms that describe natural
phenomenons or the transform operations applied to
the images [Gonzales, 1977] according to their
features. This way the *.* Group intend to reveal a
new America, invoking technological development,
Nature and Man, by means of its knowledge and its
sensibility.
4. ACKNOWLEDGEMENTS
We thank Josué Guimaráes Ramos for his
collaboration in supplying many valuable
explanations about the interpretation of satellite
images. We also thank the Fundaçäo CTI - Centro
Tecnolégico para Informética for its support in
supplying hardware, software and data for this
development.
5. BIBLIOGRAPHY
Franke, H., 1987
The Beauty of Fractals
Springer-Verlag
Laurentiz, P., 1991
A Holarquia do Pensamento Artístico pp. 93 - 101
Editora da UNICAMP - UNICAMP - cep 13083 - Brazil
Gonzalez, R. C. and Wintz, P., 1977
Digital Image Processingpp. 13 - 114
Addison-Wesley Publishing Company, Inc.
Reeves, W., 1983
Particle Systems - A Technique for Modelling a Class
of Fuzzy Objects
ACM Computer Graphics, V. 17, N. 3
Sins, K-, 1990
Particle Animation and Rendering using Data Parallel
Computation
Computer Graphics, V. 24, N.4, August