Schedule
July, 26 - Monday
16:30 - 17:00
Waldemar Celes
,
TeCGraf/PUC-Rio
Distributed Visualization
Nowadays, a large number of applications require multiple-display
visualization system capable of providing immersion sensation. The
common
approach to provide multiple synchronized views uses a powerful
centralized
processing unit to support the rendering process on all screens. This
talk
focuses on an alternative approach: a distributed architecture that
supports a
flexible and reliable visualization system.
First, we briefly introduce some issues related to virtual world
modeling and
discuss different ways to store the scene, its components and
appearance. We
then extend the discussion to model animation and its importance in a
distributed environment.
We also present a few concepts related to virtual world visualization
such as
user-observer mapping and immersion sensation. Finally, we describe the
distributed approach we have been using to achieve multiple-display
system
that, while giving the users a sensation of immersion, uses
heterogeneous
network of low-end graphics workstations.
17:00 - 17:30
Marcelo Walter
,
Universidade do Vale do Rio dos Sinos - UNISINOS
Integrating Shape and Pattern in Mammalian Models
The giraffe and its patches, the leopard and its spots,
the tiger and its stripes are spectacular examples of
the integration of a visual pattern and a body shape.
We will present in this talk a method for integrating
a pattern generation system with a body growth and
animation system.
The pattern generation system
can deliver a variety of animal coat patterns which
are quantitatively validated and biologically plausible.
The growth and animation system uses experimental
growth data to produce individual bodies and their
associated patterns automatically.
We use the example of the giraffe to illustrate
how the approach take us from a canonical embryo
to a full adult giraffe in a continous way with
results that are realistic looking. The method also
allows a considerable amount of user control for
pattern generation and body shapes.
July, 27 - Tuesday
16:30 - 17:10
Silvio de Barros Melo
,
Universidade Federal de Pernambuco
Piecewise Trilinear Deformation of Tomographic Models
In this work we introduce an iterative method that deforms
brain models built from tomographic images. The deformation is used for
normalization purposes: individual models are deformed to match the
shape, orientation and internal morphology of a reference model. In this
method the individual and the reference models are each enclosed in a
cube which is subdivided to form a rectangular grid. The vertices in the
individual models grid are perturbed and the contents of each cell is
then trilinearly mapped into a cube. The composite of all resulting
cubes form the deformed model to be compared with the reference. The
perturbations on the vertices are generated by a simulated annealing
optimization technique. To maximize the performance the models are
represented in a multi-resolution fashion and the method is paralleled.
17:20 - 18:00
Geovan Tavares
,
Laboratorio MatMidia, PUC-Rio
Volume Modeling and Aplications
In recent years a wide class of problems in biology, medicine,
geology, geophysics, among others, has demanded the handling of a huge
amount of data. This kind of data, even though they have, typically,
some organization, they are hard to parametrize in order to make a flow
in/flow out of meaningful information.
In this talk we will show how to design a mathematically sound data
structure which integrate in a unique computational environment surface
and volume modeling, and visualization.
Issues like data acquisition, image processing, edge detection,
tridimensional reconstruction and rendering will be addressed.
We will also point out how those ideas are applied on solve problems in
petroleum geology and the medical sciences.
July, 28 - Wednesday
16:30 - 17:10
Cicero Mota
,
Universidade do Amazonas
Curvature Operators in Vision and Image Processing
A frequently used method in vision and imagem processing is the use of
a linear operator to transform images. Such success, in part, comes from
the simplicity in computing with these transforms. In spite of the
successful use of linear methods, it is well known that some visual
sistems
cotain cells which are insensitive to image features whose variation is
punctual or unidirectional. Linear operators can not offer an adequate
model of these cells, thus the use of non-linear operator becomes a
necessity. Experiments reveal that most of the information carried by an
image is located in the points which are extrems of the curvature.
Based
in those experiments, C. Zetzche, E. Barth and B. Wegmann present a
detailed study of the limitations of linear operators and propose the
use
of the Gaussian curvature of the image surface as good non-linear
operator
for perceptual studies. Therefore the study of this operator and its
inverse
assumes a fundamental role in their proposal. Also, the authors
conjecture
that the set of non-zero Gaussian curvature contains the necessary
information to reconstruct the image completely. We address this
question
in both a continuos and numerical viewpoint.
17:20 - 18:00
Dibio Leandro Borges
,
Universidade Federal de Goias
In search for identifying Salient Visual Features
The problem of identifying which features are the most
important for Computational Vision tasks is a difficult, and yet
unsolved one. Although there are differences in the way they are
computed, and the constraints used, visual features such as edges and
curvatures are believed to be important cues for most visual perception
algorithms. One central question to this is how, and in what level of
detail or scale, it is possible to identify which features retain more
information, or putting it in another way are salient to the observer.
In this talk we address this question by proposing that the observations
could be made throughout a multiresolution framework, where we detect
edges and curvatures of the observed objects in different scales, and
measure from one scale to another the features with highest entropy.
The salient features of edges, and of curvatures could then be
identified as being the ones with the highest information content. We
show and analyse results in face and outdoor images.
July, 29 - Thursday
16:30 - 17:10
Luiz Henrique de Figueiredo
,
Laboratorio Visgraf - IMPA / LNCC
Interval methods for ray casting implicit surfaces with affine arithmetic
We study the performance of affine arithmetic as a replacement for
interval arithmetic in interval methods for ray casting implicit
surfaces. Affine arithmetic is a variant of interval arithmetic
designed to handle the dependency problem, and which has improved
several interval algorithms in computer graphics.
See also http://www.tecgraf.puc-rio.br/~lhf/sib99/
17:20 - 18:00
Paulo Cezar Pinto Carvalho
,
IMPA - Instituto de Matematica Pura e Aplicada
Interactive terrain visualization using client-server architecture
Interactive terrain visualization is useful for various applications
such as Geographical Information Systems, military training, city
planning
and tourist information systems.
In most of these cases, it is natural to use a Client-Server
architecture,
in which the data, usually very large, is stored in one or more
servers, that respond to requests made by client programs running
on the users' machines.
This work addresses the various techniques -- data storage schemes,
network communication,
data visualization and interaction control -- employed in such systems.
Based on this discussion, an application to allow visualization of large
terrain data
over a local network was developed.
This system adopts a multi-resolution representation for the terrain
data.
This allows interaction between user and application to
be kept high, regardless of the size of the data, due to the use of
algorithms
which select the proper level
July, 30 - Friday
16:30 - 17:00
Romildo Jose da Silva
,
Universidade Federal do Ceara
Video Cut Detection Using Differential Geometry
We introduce an algorithm to detect cuts in video
sequence. The algorithm is based on volumetric processing
of video sequence, and uses techniques from differential
geometry to classify the cut frames. The volumetric
approach allow us to capture the intrinsic coherence
of consecutive frames in a video shot, enabling thus a
robust detection of video cuts. The algorithm is very
robust with respect to the presence of noise, and avoids the
detection of "false cuts" in video shot.
17:00 - 17:30
Antonio Oliveira
,
COPPE-UFRJ
Dual and Topologically Adaptable Snake Models
In this talk we first present an edge definition based on
Riemannian geometry concepts wich can be applied for vector-valued and
single-valued images. This definition can be used to present some edge
detection methods which can be formulated using isotropic (or
anisotropic) diffusion processes. We use that more general
characterization of an edge when introducing
the parametric snake models for boundary extraction. These models
consist of an elastic curve (or surface) which can dynamically conform
to object shapes in response to internal forces (elastic forces) and
external forces (image and constraint forces). These forces are either
related to a functional minimization process or obtained on basis of
local information. Due to the non-convexity of the energy functional,
obtaining a global extremun can require the use of techniques for
rejecting local minima. Among these techniques we focus the Dual Snakes
one. Next, we introduce the Topologically Adaptable Snakes (T-snakes)
which have the ability of dealing with topological changes. In this
framework the snakes can either split or merge. Finaly, we present some
experiments using the snake models described above.
17:30-18:00
Junior Barrera
,
IME-USP
Automatic Design of Morphological Operators for Motion Segmentation
A problem of interest in digital video edition is the elimination of
moving objects from one video and the introduction of pieces of other videos
in their places. A fundamental problem to build computational tools for
this purpose is the segmentation of moving objects. In this talk, we
approach
this problem by a new technique, based on Becheur-Meyer's paradigm, with
markers detected by morphological operators designed by computational
learning. The objects in the first frames of the video are marked manually
and used
to train the markers detector. Then, the operator designed is used to
mark the objects in other frames and Beucheur-Mayer's paradigm is applied
to all frames marked by the detector. Some synthetical and real world
examples illustrate the application of the technique proposed. Complex
sistuations as oclusion are examined.