WSCG '2005: Posters

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    Segmentation of complex shapes by adaptive energy forces
    (Václav Skala - UNION Agency, 2005) Zhou, Huiyu; Liu, Tangwei; Lin, Faquan; Yusheng, Pang; Wu, Ji; Skala, Václav
    The classical gradient vector flow technique, to some extent has the ability to catch up dynamic topological changes, and therefore to extract complex shapes. Due to the reliance on the detected edges and the corresponding strength, the snake may be obstructed to rest on the ideal contours. To remedy these two deficiencies, a new deformable model is proposed in this paper. The idea is to improve the energy function by consistently reducing the Euclidean distance between the initial centroid and the estimated one of the snake. This is achieved by applying the mean shift for estimating the varied centroid of the snake during the iteration, which indicates the balance point of the overall forces. Experimental results show favorable performance of the proposed approach.
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    Classification techniques in pattern recognition
    (Václav Skala - UNION Agency, 2005) Zheng, Lihong; He, Xiangjian; Skala, Václav
    In this paper, we review some pattern recognition schemes published in recent years. After giving the general processing steps of pattern recognition, we discuss several methods used for steps of pattern recognition such as Principal Component Analysis (PCA) in feature extraction, Support Vector Machines (SVM) in classification, and so forth. Different kinds of merits are presented and their applications on pattern precognition are given. The objective of this paper is to summarize and compare some of the methods for pattern recognition, and future research issues which need to be resolved and investigated further are given along with the new trends and ideas.
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    Generalized Hebbian learning for ellipse fitting
    (Václav Skala - UNION Agency, 2005) Wijewickrema, Sudanthi N. R.; Papliński, Andrew P.; Skala, Václav
    In this paper, we investigate the use of a neural network employing Genralised Hebbian Learning for the approximation of an image of a hypothetically ellipsoidal object as an ellipse. Further, we discuss how the same algorithm is used with higher dimensional data to model hyperellipsoids, with the basic aim at a specific application, namely the modelling of an object as an ellipsoid given a set of 3-dimensional points.
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    Anatomy-based human face reconstruction using multi-layer deformation
    (Václav Skala - UNION Agency, 2005) Zhang, Yu; Sim, Terence; Sung, Eric; Skala, Václav
    We present a method for reconstructing anatomy-based facial models with minimal manual intervention. The technique is based on deforming a multi-layered prototype model to the acquired surface data in an “outside-in” manner. It enables a variety of applications, including texture transfer, morphing, statistical analysis of the face shape, and face recognition database satisfying large extra- and intra-subject variations.
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    A study on a cyber world for language acquisition and sensory information transfer control
    (Václav Skala - UNION Agency, 2005) Katayama, Yuya; Okada, Minoru; Skala, Václav
    In this paper sensory information transfer methods for sight, sound, and text chat are proposed. The authors have studied a foreign language acquisition system Orbis utilizing cyber worlds. For such a system, realistic communication, and the server CPU load and the network traffic become important issues. A concept of communication space to control sensory information in a cyber world is introduced and discussed.
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    Principal component analysis for the approximation of an image as an ellipse
    (Václav Skala - UNION Agency, 2005) Wijewickrema, Sudanthi N. R.; Papliński, Andrew P.; Skala, Václav
    In this paper, we investigate a method of using principal component analysis(PCA) to fit an encapsulating ellipse to the image of a hypothetically ellipsoidal object. This technique is aimed at applications such as fruit sorting, where resource constraints and speed requirements necessitate the approximation of data.
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    Robust optical measurement of dust thickness on a flexible filter surface
    (Václav Skala - UNION Agency, 2005) Uray, Martina; Rüther, Matthias; Bischof, Horst; Skala, Václav
    A stereo computer vision system as a thickness measurement device is introduced. The challenging task is to measure the thickness of dust deposits over the surface of a flexible cloth filter with a target resolution of 0.5 mm2 per measurement in the filter plane and a depth resolution of up to 50 μm. The total area to be measured is 100 mm × 2500 mm. There is practically no texture present on the dusty filter surface. Analyzing dust deposition over the whole filter length during operation has not been possible so far and promises to give insight to air flow in the filter chamber, behaviour of different filter materials and design flaws of filter chambers. Our approach is to first create dense 3D-reconstructions of surface patches. This is done using a calibrated stereo setup and a standard slide projector that provides texture by projecting a random pattern onto the filter surface. The thus obtained surface patches are registered against each other using an ICP algorithm to get a complete 3D model of the filter surface. This step is done twice, for the clean filter surface and for the surface including dust deposits. We finally retrieve the actual depth information by registering the clean and dusty models using markers applied to the filter surface and calculating the difference. In this paper we present the measurement device as well as the underlying vision system and show that it is possible to meet the given requirements under industrial conditions.
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    A flexible approach to non-homogeneous texture generation
    (Václav Skala - UNION Agency, 2005) Taponecco, Francesco; Rieger, Thomas; Skala, Václav
    Due to the numerous applications, textures reserve significant interest in many scientific fields. Several recent works concentrate in the analysis and synthesis of textures, and they still are a very active and actual area of research in Computer Graphics. In this work, we propose a pixel-based technique, which allows the production of smooth textures and a precise patterns’ visualization. Textures’ patterns may move or vary along given directions or may progressively change their appearance. We implemented our algorithm incorporating much functionality in a general framework; this framework offers the possibility to generate non-homogeneous textures in a flexible and interactive way. Integrating artistic effects and performing a frames’ animation is also possible, allowing the production of a variety of effects in an easy and general way.
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    A tracking algorithm for rigid point-based marker models
    (Václav Skala - UNION Agency, 2005) Schwald, Bernd; Skala, Václav
    Tracking of objects and persons by using a stereo camera system setup and markers is applied since several years in Virtual and Augmented Reality or other applications. In especial infrared tracking systems are getting increasingly popular, because of their precision and robustness. Often, markers for such systems are spherical and therefore not distinguishable, making the consideration of geometric constellations of several markers necessary to identify objects and to determine their transformations. This paper presents an algorithm for tracking rigid constellations of markers, which can be adapted to the needs of corresponding applications.
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    Real-time simulation of autonomous vehicles on planet-sized continuous LOD terrains
    (Václav Skala - UNION Agency, 2005) Sumengen, Selcuk; Balcisoy, Selim; Skala, Václav
    Real-Time visualization of interactive simulation environments using large datasets of height fields became feasible using current off the shelf graphics hardware. Our approach provides continuous level of detail rendering of high detailed, planet sized terrains using restricted quad-trees without re-sampling data points. The presented method preserves the original planet coordinate frame of the data gathered from the Mars Orbiter Laser Altimeter with 128 samples/degree resolution for vehicle simulation purposes. Furthermore the algorithm avoids discontinuities at the block boundaries occurring at latitudes.
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    Modeling with rational Bézier solids
    (Václav Skala - UNION Agency, 2005) Samuelčík, Martin; Skala, Václav
    In this paper we present a technique for modeling solids based on the rational trivariate Bézier expressions. These solids are defined by analytical expression. For modeling purposes we focus on rotational, transitional and twisted solids. Final visualization is then done by approximation of solids by net of points and by boundary evaluation of solid. We also present practical output of our visualization algorithm.
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    CyberSession: a new proposition for e-learning in collaborative virtual environments
    (Václav Skala - UNION Agency, 2005) Sadeghi, Javad; Aavani, Amir; Sharifi, Mohsen; Skala, Václav
    E-Learning in fact is another type of learning process through the integration of technology and is perceived as learning via a web browser, over the web or an intranet network. E-Learning in the context of 3D virtual environments promises better performance in the light of new trends for 3D environments among users. This paper presents the design and first steps to the implementation of a collaborative environment representing course materials through web3D technologies. It highlights the unique ability to run in low bandwidth by simulating user input and transforming work forces into a knowledge resource. In our framework, nicknamed CyberSession, users can switch between 2D and 3D environments to support synchronous training, asynchronous training and collaborative training systems.
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    Layer-based decompositions of polyhedra
    (Václav Skala - UNION Agency, 2005) Rueda, A. J.; Martinez, F.; Feito, F. R.; Skala, Václav
    This work describes a decomposition scheme for polyhedra called Layer-based decomposition. This decomposition can be computed in a efficient way for any kind of polyhedron, and has interesting applications in several geometric problems, like Boolean operation computation, point-in-polyhedron inclusion test, 3D location and rayscene intersection computation.
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    A low cost structured light system
    (Václav Skala - UNION Agency, 2005) Reiss, Mário L. L.; Tommaselli, Antonio M. G.; Kokubum, Christiane N. C.; Skala, Václav
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    Simulation of blur in stereoscopic image synthesis for virtual reality
    (Václav Skala - UNION Agency, 2005) Piranda, Benoît; de Sorbier, François; Arquès, Didier; Skala, Václav
    This paper proposes a method permitting to generate synthesized images including blurred area in real time in order to help stereoscopic perception in virtual reality systems. At any time of the process, the combined knowledge of the scenario and the position of the user in front of the screen allows to select automatically the important zone of the scene. The elements associated to the clear zone catch the attention of the user while the blurred areas avoid an excessive eyestrain. First, we present several methods permitting to simulate blur effects produced by a thin lens in image synthesis. Then we develop our work on the adaptation of the previous methods in the stereoscopic images context, illustrated by results generated in our own virtual reality system. Finally, we propose different solutions for the treatment of the interdependence between scenario and interactivity in image synthesis animations.
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    Ultrasonic diffraction tomography: the experimental result
    (Václav Skala - UNION Agency, 2005) Pintavirooj, C.; Jaruwongrungsee, K.; Withayachumnankul, W.; Hamamoto, K.; Daochai, S.; Skala, Václav
    Diffraction tomography is a technique for imaging with acoustic fields. It takes advantage of the linearization process of the non-linear wave equation describing wave propagation in heterogeneous media. When the scattering effect is weak, one can invoke the Born or Rytov approximation and thus derive the generalized Fourier Slice Theorem to reconstruct the cross-section of the insonified object. Although diffraction tomography is a promising technology for medical application as it provides a quantitative ultrasonic image, its realization toward medical use is still far-to-go, this may be due to the complexity of the hardware involved. In this research we investigate a potential use of diffraction tomography for medical application by using a delicate-designed ultrasonic computerized tomographic system. The result of experiment investigation of diffraction tomography is very promising.
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    Different levels of interaction in a virtual environment
    (Václav Skala - UNION Agency, 2005) Oyarzun, D.; Ortiz, A.; Skala, Václav
    The widespread use of electronic devices in the daily tasks has motivated the research in user interfaces. The conversational user interfaces using virtual characters are starting to be widely used in order to improve the human-computer communication, due to the illusion of having a conversation with a real human. Our approach is based on having an avatar as the main interaction element in the virtual environment. Thanks to the virtual characters we can “connect” all the components in the system, such as user, VE and avatars, and having a high level of interaction. In one hand, the user can interact with the avatar and with the environment. In the other hand, the avatars can interact with the user or behave in an autonomous mode, interacting between them. Having this kind of interaction implies the development of animation techniques, path finding, collision detection, human behaviours, etc. The techniques implemented for achieving the different levels of interaction are also explained in this paper.
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    Automatically generating 3-D image imagined from drawing lines
    (Václav Skala - UNION Agency, 2005) Morita, Satoru; Skala, Václav
    In the paper we automatically create three-dimensional image using the occluding contours that exist in a viewed image. We propose a new method to generate the surface based on the rules needed to reconstruct the stable surface known in the psychology field from the occluding contours. The method is useful because it can be used as a modeler in computer graphics.
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    A flexible and modular architecture for object space NC-Machining simulation
    (Václav Skala - UNION Agency, 2005) Moreno, Aitor; Toro, Carlos; Arizkuren, Iosu; Segura, Alvaro; Posada, Jorge; Novo, Marcelino; Falcón, Juanjo; Alcaín, Nieves; Skala, Václav
    The NC machining processes based on computer graphics is a significant part of modern Computer Integrated Manufacturing (CIM). Through simulation, it is possible to test the correctness of the NC tool paths without the need of machining actual physical parts, with the corresponding reduction of time and costs. In this paper, we present a flexible and modular architecture that describes a generic object-based NC machining simulation system. This architecture has been tested using several object-based simulation approaches, and could be successfully integrated in commercial simulation systems. This work also covers other proposed architectures found in the literature.
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    Low cost avatars animation system from real images compliant MPEG4
    (Václav Skala - UNION Agency, 2005) Mir, B.; Salas, A.; Jaume, A.; Bez, M.; Perales, F.; Skala, Václav
    In this paper we present a low cost system to capture, modelization and animation of avatar face with a few control points based in FAP´s MPEG4 coordinates. A Facial Animation Engine is designed as high-level interface for the synthesis and animation of virtual faces that is in full compliance with MPEG-4. We implement the MPEG-4 standard specifications for the adaptation and animation of 3D wire-frames models with respect to the reproduction of two characteristics: realism in adapting the model geometry to the characteristics of any specific face and realism in performing facial expressions. Starting from a facial wire-frame model and from a set of configuration files, the developed system is capable of automatically generate the animation stream of FAPS (Facial Animation Parameters). Our system uses an Interpolation approach to emulate the behavior of face tissues. The final objective is to use the system in real time environments and for portable PDA, mobile phone applications or virtual reality applications.