WSCG '2002: Posters
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Item Optimized net exchange MonteCarlo simulation for participating media(UNION Agency, 2002) Perez, P.; Paulin, M.; el Hafi, M.; Fournier, R.; Skala, VáclavThe aim of this paper is to present the use of Monte Carlo method in engineering applications to solve the radiative transfer equation in participating media. Adapted probability density functions that allow to optimize the Monte Carlo algorithm are discussed. 1D and 2D test cases are treated and a validation work has been performed. The 3D implementation is in progress.
Item A surface reconstruction approach based on multi-resolution methods and T-surfaces framework(UNION Agency, 2002) Strauss, E.; Jiménez, W.; Giraldi, G.; Silva, R.; Oliveira, A.; Skala, VáclavIn this paper we present a new approach which integrates the T-Surfaces framework and a multi-resolution method in a unified methodology for segmentation and surface reconstruction. For noise images, we can improve the result by anisotropic diffusion. Despite this improvement, some manual intervention may be required to complete the reconstruction. Thus, we take advantage of the topological capabilities of T-Surfaces to enable the user to modify the topology of a surface. We test the method for synthetic and medical volumes images.Item Camera calibration using neural networks(UNION Agency, 2002) Mendonça, Márcio; da Silva, Ivan N.; Castanho, José E. C.; Skala, VáclavThis work presents a procedure for camera calibration using artificial neural networks of the type back propagation perceptron. Camera calibration is employed in computer vision for pose determination and it requires a solution of non-linear system of equations. By employing neural network, it becomes unnecessary to know the parameters of the cameras, such as focus, distortions besides the geometry of the system. Camera simulations and real experiments are used to demonstrate and evaluate the procedure.Item Watershed transformation: reducing the over-segmentation problem by applying noise resucer and region merger(UNION Agency, 2002) Vanderstockt, Yann; Whyte, R. N.; Skala, VáclavImage segmentation is used to identify homogeneous regions in an image, it has been a subject of research for the last three decades. It is usually the first, and most difficult task for any image understanding system. Image segmentation is usually associated with pattern recognition problems and is considered the first phase of such a process. Consequently, the success of the pattern recognition process is dependent on the quality of this initial stage. Here we examine image segmentation. We describe the watershed transformation algorithm and our variation of it. We provide results for our implementation and compare then to previously published results from traditional implementations of the watershed transformation. Finally, we believe that these results substantiate the case that our modifications to the watershed provide much improved segmentation results.Item DEMEDITOR: a tool for editing DEMs(UNION Agency, 2002) Teichrieb, Veronica; Frery, Alejandro C.; Kelner, Judith; Skala, VáclavA system to visualize and edit digital elevation models based on interferometric synthetic aperture radar data is presented. The visualization and exploration of digital elevation models has been basically done through the use of two-dimensional interfaces. As virtual reality interfaces have proven to offer a high degree of presentation realism and several interaction facilities, they are an appropriate way to visualize and interact with objects such as terrain models. The realistic presentation of the height component of such kind of object is fundamental for its comprehension. Digital elevation models frequently present elevation errors due to problems occurred during imaging process or raw data processing. Several methods have been developed to correct these errors, but a total elimination is not much probably. The visual interpretation of the data, the use of analyse tools to assess this interpretation, and the manual editing of error areas in the digital elevation model compose the error reduction procedure presented by this work. The system offers both a two and three-dimensional interface to visualize and interact with the digital elevation models, and allows the selection of error areas in the terrain in order to remove them. The removed areas can later be interpolated and smoothed.Item Graphic simulator for adversary adaptive agents in war environments with real time parallel processing(UNION Agency, 2002) Silva, Adriano C. D.; Skala, VáclavThe presented paper is part of a prototyping effort in the sense of searching solutions for combat systems, where through the use of virtual reality and feedback control techniques is provided a real time aircraft decision system for an operational combat environment. Using virtual reality to develop the prototyping and simulation for highly complex systems is quite advantageous, once that it provides an appropriated system follow up with lower cost and higher safety.Item A variational representation for efficient noisy segmentation(UNION Agency, 2002) Romano, R.; Vitulano, D.; Skala, VáclavIn this paper we focus on a novel technique VRENS, (Variational Representation for Efficient Noisy Segmentation) to segment images (i.e. containg also textures) under noise. It is based on a hierarchical representation obtained by a combination of the classical weak membrane and a simpler region competition method. VRENS seems to be an interesting algorithm because of its robustness to added gaussian noise along with a low computational cost.Item Real-time clothing: geometry and physics(UNION Agency, 2002) Rudomín, Isaac; Castillo, José Luis; Skala, VáclavThis paper describes a technique that allows pieces of clothing to be placed over an animated articulated character in real-time. In order to do this, the character to be dressed must be approximated using a hierarchy of ellipsoids. The pieces of clothing are represented using mass-spring particle systems; the particles move by applying dynamic forces to them and integrating the system with an explicit method. Penetration of the character’s ellipsoids by any particle are avoided; to facilitate and accelerate these calculations the ellipsoids are arranged in groups and an adjacency graph is constructed between these groups. This method is fast enough to deliver real-time performance on mid-range PCs and workstations, using only portable and standard C++ and OpenGL code.Item Weighted multiple bit-plane matching, a simple and efficient matching criterion for electronic digital image stabilizer application(UNION Agency, 2002) Pourreza, H. R.; Rahmati, M.; Behazin, F.; Skala, VáclavIn this paper we propose two new matching criteria for template matching. The performance evaluation of these two criteria is applied to electronic digital image stabilizer (EDIS) application. These two criteria are based on bit-plane matching (BPM) criterion, where four decimated bit-planes are used in our criteria. These criteria can be realized using only Boolean functions; hence they can be realized very simple in any digital systems. We compared our criteria with other known criteria by employing twenty real video sequences.Item 3D-shape reconstruction based on radon transform with application in volume measurement(UNION Agency, 2002) Pintavirooj, Chuchart; Sangworasil, Manas; Skala, VáclavIn this paper, we have adopted a novel method for 3D-shape reconstruction. We derived a volumetric data which is constructed from a stack of cross-section images- the so-called tomographic image. Each of the cross-section images is computed from a series of photographs taken at a number of angles around the object. A corresponding intensity profile (row) on each digitized photograph resembles a projection data, which can be used to reconstruct the cross-section image. Once the volumetric data is obtained, isosurface of the object is extracted using the well-known marching-cube algorithm before being rendered with a conventional surface-rendering technique. Unlike conventional 3D-shape reconstruction (3Dshape recovery) method of using stereo pairs of camera, our technique does not suffer from laborious corresponding problem. Nor does it require a sophisticated scanning system as it does in the laser range finder. Our purposed method is tested to perform 3D-shape reconstruction of a variety of objects. The application of our purposed method for volume measurement is also presented in this paper. The results are very promising.Item Ambiuous digitizations by dilation(UNION Agency, 2002) Lincke, C.; Wüthrich, C. A.; Skala, VáclavThis article deals with ambiguous surface digitizations by dilation in n-dimensional space. The digitization of a sufficiently regular surface is separating but not necessarily minimal. We will determine conditions under which the supercover and the grid intersection digitizations are discrete surfaces. It will also be proven that non-overlapping domains do not solve the problem of simple points in digitizations. No matter howthe digitizationdomain is chosen therewill occur ambiguous cases which have to be treated differently.Item Architecture of system for configurable GIS data compression(UNION Agency, 2002) Komzak, Jiří; Slavík, Pavel; Skala, VáclavThe paper deals with formal description of data transformation (compression and decompression process). An adaptive compression tool for different data types (both raster and vector), that is based on finite automata, is introduced. When using distributed geographic information system (GIS), data of different types has to be transmitted. The introduced tool enables flexible changes of compression method and selective loss control during compression process. Finite automata are discussed for several dictionary and other string-based compression methods. Application of one dimensional compression methods in the field of computer graphics is discussed.Item Rule-based modeling for 3D GIS(UNION Agency, 2002) Kim, Sung-Soo; Lee, Seong-Ho; Park, Jong-Hyun; Yang, Young-Kyu; Skala, VáclavOne popular approach for modeling 3D geo-features is to create 3D CAD model manually. In particular, manual 3D geo-feature modeling approach provides a high quality of visualization for 3D GIS features. However, this approach can be time consuming to generate 3D models being created manually and requires high costs. We introduce a novel modeling concept; so-called, Rule-based modeling (RBD) that can model 3D geo-features using 2D profiles and 3D feature attributes. By using rule-based engine and model library, we are able to create 3D geo-features automatically. The RBD component combines a synthetic modeler with efficient LOD (level-of-detail) control for real-time rendering. In addition to, describing the details of our component, we present the comparison result between manual modeling and proposed rule-based modeling in terms of the following criteria: input data domain, interoperability, reusability and modeling cost.Item Classification of systems for simulation and visualization of physical phenomena(UNION Agency, 2002) Chludil, Jiří; Žára, Jiří; Skala, VáclavThe paper provides an overview and a comparison of several tools for visualization of physical simulations. We concentrate on new visualization tools and architectures that have been developed during last years (VRToolBox, VRML + Java, etc.). Classification of these approaches is presented together with practical examples including authors’ subjective opinion. This overview has been prepared with respect to visualization in three-dimensional virtual environments.Item An approach for a campus visualization system(UNION Agency, 2002) Hetze, Bernd; Hübsch, Gerald; Kohlschmidt, Horst; Skala, VáclavIntense work is spent especially in the fields of city planning and tourist information to examine possibilities for combining generic information with graphic data to enhance computer based information desk systems. This article presents an approach towards the creation of a campus information system. This campus information system shall allow the user to navigate and select information with the help of a user interface that integrates possibilities to use 2D and 3D interaction concepts simultaneously. The VR entities are accessed by user interaction via the render window.Item Reconstruction filters for bump mapping(UNION Agency, 2002) Hast, Anders; Barrera, Tony; Bengtsson, Ewert; Skala, VáclavTextures that are magnified appears jagged, and therefore reconstruction filters using linear or cubic interpolation polynomials are often used to reduce aliasing. The same aliasing problem is noticed for bump mapping, where it is often solved by bilinear interpolation of the height map, in order to obtain intermediate values. Low-pass filtering of the height map is not suitable for the magnification problem since it will suppress the bumps. It will be shown that reconstruction filters can be used to interpolate gradients, rather than height values directly. The goal is to produce non jagged bumps, without removing high frequency details by low-pass filtering.Item An approach to real-time plant creation(UNION Agency, 2002) Danaher, Maurice; Creemers, Warren; Skala, VáclavIn this paper methods are presented for the visualisation of plant life for games and other graphics simulations in real time. Current systems generally use a very limited number of models of plants that are created in advance and loaded into the system at execution time. Real-time generation saves disk space and allows for a great variety of plants to be used in a game. The methods described here will allow the creation of interesting and varied plant life and thus produce a far richer, more appealing and engrossing environment for users.Item A graphical user interface framework for digital television(UNION Agency, 2002) Pablo, César; Petri, Vuorimaa; Skala, VáclavCurrently, the number of non-PC devices used for interactive applications is increasing. Digital television set-top boxes, PDAs, and mobile phones are typical examples. Interactive applications are controlled via a Graphical User Interface (GUI). Consequently, a GUI framework is required. The objective is a unified GUI framework for all these new devices. Since one of the new devices is digital television, an implementation of a digital television GUI framework is presented. It has been developed following the HAVi specifications. Its main characteristics are use of Java, separation of look and feel, and lightweight widgets. The implementation is tested with a digital television application. The main conclusion proposed is that new devices should use a device-oriented GUI framework implementation. Moreover, specific implementations can be obtained by modifying the look or feel of the widgets.
