Computer Graphics, Image Processing, and Vision, 1998. Proceedings. SIBGRAPI '98. International Symposium on

This paper summarizes work done in our laboratory with a special emphasis on functional aspects of the visual field. The quality of the perceived image within a visual display depends on the information available within the display itself but also on the capacity of the human visual system to process visual information. Specifically, the paper discusses work on human visual processing which deals ... View full abstract»

We briefly describe advancements in two broad areas of morphological image analysis. Part I deals with differential morphology and curve evolution. The partial differential equations (PDEs) that model basic morphological operations are first presented. The resulting dilation PDE, numerically implemented by curve evolution algorithms, improves the accuracy of morphological multiscale analysis by Eu... View full abstract»

Computer animation is a multifaceted field of computer graphics. This presentation explores one of these facets. At first computer animation is surveyed through the use of a framework to help to order and classify its main approaches related to movement modeling. Then the use of Petri nets as a modeling and simulation tool to obtain some kind of foresight of a developed animation is discussed. View full abstract»

Optimal filters are characterized by parameters based on image and filter structure and these parameters need to be estimated from realizations. For fully optimal mean-absolute-error binary filters, conditional expectations need to be estimated. Owing to lack of estimation precision, the resulting estimated filter is likely to be suboptimal. The estimation dilemma can be mitigated by using a const... View full abstract»

We present a novel class of morphological filters, which are ideal simplification tools in order to facilitate the segmentation of objects of interest. As a subclass of connected operators, they are particularly interesting for segmentation purposes, as they suppress many details in the image while preserving perfectly the position and the sharpness of the structures which are not suppressed. Furt... View full abstract»

In the advent of the ubiquity of distributed computing with multimedia capabilities, it is very natural to contemplate collaborations that were not previously possible. In the past scientists, doctors, educators, engineers always had need to share, exchange, debate their work, designs, methodology, knowledge and experience. This was commonly done by attending meetings, publishing in common journal... View full abstract»

This paper presents a system for three-dimensional image reconstruction based on the combination of both adaptive and wavelet reconstruction methods and the use of B-wavelets function for interpolation. Results show the usefulness of the system for three-dimensional image reconstruction and also after interpolation with data obtained by X and /spl gamma/-ray computerized minitomograph scanners for... View full abstract»

Geometric accuracy of a close-range photogrammetric system is assessed in this paper considering surface reconstruction with structured light as its main purpose. The system is based on an off-the-shelf digital camera and a pattern projector. The mathematical model for reconstruction is based on the parametric equation of the projected straight line combined with collinearity equations. A sequenti... View full abstract»

The reconstruction of a 3D model from range images can be conveniently split into two stages. The first stage consists basically in the extraction of geometrical information, e.g. the depth and the orientation of image points, and the second stage concentrates on the transformation of these data to a 3D model. We focus on the second stage. Our approach is based on a deformable model, which offers ... View full abstract»

This study presents a technique for quantitative enhancement of both linear attenuation coefficients and visual features of maps obtained from multiple energies using tomographic systems. The quality of images obtained by computerized X-ray tomography in multiple energies is limited due to the number of noise pixels in the images. The method developed uses enhancement techniques with adaptative fi... View full abstract»

In this paper, we use partial differential equation based analysis as a methodology for computer-aided cytology. We wish to accurately extract and classify the shapes of nuclei from noisy confocal microscopy images. This is a prerequisite to an accurate quantitative intranuclear (genotypic and phenotypic) and internuclear (tissue structure) analysis of cancerous and pre-cancerous specimens. We stu... View full abstract»

In this work we study algorithms for obtaining simplified representations of terrain models. Terrain data is difficult to deal with, due to its complexity and size. Simplification methods are some of the techniques used to reduce its natural complexity. Among these methods, greedy insertion with vertical local error measure is considered to be the one that yields best results. In spite of its qual... View full abstract»

We present an algorithm for intersecting finite-element meshes defined on parametric surface patches. The intersection curves are modeled precisely and both meshes are adjusted to the newly formed borders. The algorithm is part of an interactive shell modeling program, which has been used in the design of large offshore oil structures. We avoid unacceptable interaction delays by using a variant of... View full abstract»

The point containment predicate which specifies if a point is part of a mathematically defined shape or not is a crucial problem in computer graphics. This paper presents a stroking technique that counteracts the main disadvantage of point containment algorithms: their quadratic time complexity with increasing resolution. It is also presented an efficient algorithm to perform simultaneously the fi... View full abstract»

The main focus of this work is on the development of incremental graph-based techniques for satisfying a coupled set of engineering and geometric constraints. The objective is to speed up a constraint-based design. A prototype constraint-based system has been developed to demonstrate the feasibility of these incremental algorithms. The proposed techniques were applied to the internal-combustion en... View full abstract»

We present a general cache management algorithm with data pre-loading that optimizes access to data in real-time applications. We show that our algorithm provides the optimum results when the visualization sequence is known. We also present an oracle that estimates the visualization sequence for 2D data sets, and show the results of the algorithm in a virtual panorama viewer. View full abstract»

This paper presents an application of the virtual reality paradigm to scientific visualization. We describe how the seismic interpretation task performed in oil and gas companies can be facilitated by using immersion techniques inherent to virtual reality. The feeling of immersion allows an easier and better understanding and manipulation of the three-dimensional data associated with seismic inter... View full abstract»

The use of computer graphics techniques in visualization is hampered by the complexity of data, display limitations and the difficult process of establishing adequate mappings. One way to compensate for the difficulties in handling data and image complexity is to turn to users' capabilities and human factors, and to revisit visualization and interaction techniques under such premises. This paper d... View full abstract»

This work reports developments on a system for 3D visualization based on "Holoprojection", a depth coding technique. This system allows visualization using several planes of depth of textured images, such that all depth cues are present under certain limits. The 3D volume can be observed with no auxiliary devices, such as stereo glasses. View full abstract»

Oil reservoirs searching is based on several exploratory methods, which produce a large quantity of data that must be interpreted and analyzed by geologists. Graphic systems can help these tasks by providing three-dimensional representations to convey information in a more natural and efficient way to the users. Therefore, they are typical scientific visualization applications. This paper presents... View full abstract»

Computational visualization systems and techniques have improved information gathering activities and changed the ways in which science is studied. However, the complexity of the data handled by such systems has suggested the need for alternative representation and display techniques. Auditory display has been considered to be a real possibility in this area, in a field known as sonification. The ... View full abstract»

Due to the concentration of users in certain regions of the virtual world, distributed virtual reality systems-DVRS-may become unbalanced, resulting in low performance and bad utilization of system resources. The authors studied this problem and proposed a queueing model and load balancing algorithms to reduce these effects. Some experiments showed how the utilization and response time of the syst... View full abstract»

The author proposes an image coding algorithm that effectively combines irregular subsampling and Delaunay triangulation. A set of sampling points in the image is selected in an incremental manner and used to construct a Delaunay triangulation. Each triangular region is then approximated using linear interpolation. The coding scheme is based on run-length coding (RLC). The incremental selection of... View full abstract»

An image compression/decompression method is proposed, based on a new interpolation formula of Hermite-Birkhoff type. It is based on a function representation that uses a truncated multipoint Taylor (MT) series. Given a regularly tabulated image, first spatial derivatives (up to a chosen order) are computed by a FFT algorithm. Secondly a knot placing strategy selects sample point positions. The im... View full abstract»