WSCG '2004: Posters

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http://hdl.handle.net/11025/922

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Showing 1 - 20 out of 53 results

Non-photorealistic walkthroughs using flash
(UNION Agency, 2004) Ženka, Roman; Slavík, Pavel; Skala, Václav
We describe a method allowing users to walk through 3D scenes using Macromedia Flash player. The method is optimised for low data transfer rates and low demands on the displaying device, which makes it suited especially for mobile devices. The walkthroughs are partially pre-computed on a server and partially calculated directly on the PDA. Non-photorealistic rendering is used for more eye-pleasing results and for achieving higher data compression.
De-noising and recovering images based on Kernel PCA theory
(UNION Agency, 2004) Xi, Pengcheng; Xu, Tao; Skala, Václav
Principal Component Analysis (PCA) is a basis transformation to diagonalize an estimate of the covariance matrix of input data and, the new coordinates in the Eigenvector basis are called principal components. Since Kernel PCA is just a PCA in feature space F, the projection of an image in input space can be reconstructed from its principal components in feature space. This enables us to perform several applications concerning de-noising and recovering images. Because of the superiority of Kernel PCA over linear PCA, we also get satisfactory effects of de-noising images using Kernel PCA.
Practical construction of reflectances for spectral rendering
(UNION Agency, 2004) Wang, Qiqi; Xu, Haiying; Sun, Yinlong; Skala, Václav
We propose a method to construct practical reflectances for spectral rendering. A set of 1400 real reflectances are measured and more spectra with higher saturated colors are generated using Bouguer’s law. These spectra serve as the basis for constructing the spectra for any colors. Given a color triplet P, in the color space, we find a small local tetrahedron that contains P and the reflectances at the vertices are known. Thus the spectrum at P is constructed using trilinear interpolation. Our derived spectra correspond closely to real spectra and the transformation works for a large volume of color space. This method of spectral construction has been applied to texture mapping and simulation of wavelength-dependent phenomena in spectral rendering.
Information retrieval of color images via wavelets
(UNION Agency, 2004) Vitulano, D.; Santosa, F.; Skala, Václav
This paper focuses on a novel framework for information retrieval of images based only on color information. Regions homogeneous in color of the input image are detected using a multireso- lution analysis. In order to avoid the selection of regions having similar color, a new clustering scheme based on repulsion between electric charges, is proposed. The resulting model is completely automatic and achieves good results in terms of computational time and performances.
Robust object detection in complex backgrounds using ICA compression
(UNION Agency, 2004) Vicente, M. A.; Fernández, C.; Reinoso, O.; Pérez, C.; Skala, Václav
This paper describes a method for recognizing real three-dimensional objects in non-controlled backgrounds using independent component analysis to eliminate redundant image information present in each object image. The proposed method is a two-step process that allows a coarse color-based detection and an exact localization using shape information. The paper describes an efficient implementation, making this approach suitable for realtime applications.
Natural lighting of vegetation based on polar planes
(UNION Agency, 2004) Vicent, Mária J.; Lluch, Javier; Vivó, Roberto; Skala, Václav
We present a lighting method for outdoor scenes with vegetation. The method is compatible with multiresolution trees generated using random L-systems. We include a sky dome model that gets the luminance and chromaticity values at several sampling points for different time and location. The samples are used to compute the light arriving to the objects in the scene depending on the insolation conditions. The method proposed is based on the form factor and polar plane concepts. These concepts are used not only to illuminate leaves or ground, but to solve visibility problem too.
Real-time terrain visualization on PC
(UNION Agency, 2004) Vaněk, Jan; Ježek, Bruno; Skala, Václav
Terrain visualization is a task taking place in all geographic information systems (GIS). Very large datasets are often processed and visualized in real-time. Although the performance of hardware continually increases, it is necessary to optimize the form and the amount of 3D terrain information to obtain sufficient framerates during visualization. This article deals with choosing the appropriate terrain representation and a suitable method for large terrain data management. Proposed optimizations were successfully tested in implementation of real-time terrain visualization using a common graphic card for hardware acceleration.
Curve matching by using B-spline curves
(UNION Agency, 2004) Toe, Ted; Van To, Tang; Skala, Václav
This paper presents an algorithm for estimating the control points of the B-spline and curve matching which is achieved by using the dissimilarity measure based on the knot associated with the B-spline curves. The B-splines stand as one of the most efficient curve representations and possess very attractive properties such as spatial uniqueness, boundedness and continuity, local shape controllability, and invariance to affine transformations. These properties made them very attractive for curve representation, and consequently, they have been extensively used in computer-aided design and computer graphics. The curve matching program is shown in this paper. Any input test object curve can be matched with the B-spline sample curve. The control points of sample curve are computed and stored in the program. The test object curve, a bitmap file, is thinned then converted to B-spline curve and then to match with the sample curve.
Fractal image compression for efficient texture mapping
(UNION Agency, 2004) Stachera, Jerzy; Nikiel, Sławomir; Skala, Václav
Texture mapping has traditionally been used to add visual realism to computer graphics images. In the paper we propose an alternative technique for image texture handling. We use fractal image compression scheme to compress and decompress large and complex textures. We identify special properties of the method to apply in the very process of texture mapping. The main idea is to exploit high degree of local self-similarity in natural textures. The method allows for very high compression of complex textures, provides real-time decompression and perfectly suits Level of Detail. Properties of the method are compared to those of classical DCT and wavelet compression schemes.
Client-server infrastructure for interactive 3D multi-user environments
(UNION Agency, 2004) Soetebier, Ingo; Birthelmer, Horst; Sahm, Jörg; Skala, Václav
Multi-user environments, using 3D graphics, more and more find their way into areas like e-business, entertainment and cooperative work. Due to the increasing capabilities of hardware and network, even smaller devices, like laptop computers or PDAs, become suitable for the visualization of 3D graphics. A possible approach for distributing the 3D information is to use a server, which provides all clients with the necessary data. In this paper we define a client-server software framework, which supports the design of three-dimensional multi-user environments. We define requirements of the software infrastructure for a client-server framework that can provide a number of different 3D scenes, each with several users. The number of 3D scenes and users should be only limited by the hardware. Furthermore, we present a solution for each requirement and finally we discuss the results.
Face identification based on biological trait using infrared images after cold effect enhancement and sunglasses filtering
(UNION Agency, 2004) Siddiqui, Raheel; Sher, Muhammad; Rashid, Khalid; Skala, Václav
This paper describes face identification using infrared images and eigenfaces after passing test face through cold effect enhancement and/or sunglasses filtering algorithms and handling facial hair through threshold. Eigenface technique after modification is used to define our eigenspace. Test image before going through the recognition process has to pass through a check to see whether it is a face image or not. The test face is passed through an algorithm to check and enhance if the person come from cold and then is projected to eigenspace to find the match. If match is not found then it is passed through another algorithm to check whether person has worn sunglasses and if so the image is enhanced in order to make recognition more efficient. Only one person of the test sets is recognized wrongly with the other but both of them belongs to the training set and it gives 100% accurate results for profile images.
Improving form cactor accuracy by projecting onto the hemisphere base
(UNION Agency, 2004) Rosell, Vicente; Vivó, Roberto; Skala, Václav
In this work we introduce a new method for computing Form Factors in Radiosity. We demostrate how our method improves on existing projective techniques such as the hemicube. We use the Nusselt analog to directly compute form factors by projecting the scene onto the unit circle. We compare our method with other form factor computation methods. The results show an improvement in the quality/speed ratio using our technique.
3D shape extraction using photographic tomography with Its applications
(UNION Agency, 2004) Reruang, S.; Withayachumnankul, W.; Pintavirooj, C.; Airphaiboon, S.; Skala, Václav
Tomographic imaging is a technique for exploration of a cross-section of an inspected object without destruction. Normally, the input data, known as the projections, are gathered by repeatedly radiating coherent waveform through the object in a number of viewpoints, and receiving by an array of corresponding detector in the opposite position. In this research, as a replacement of radiographs, the series of photographs taken around the opaque object under the ambient light is completely served as the projections. From the process of tomography, the outcome is the stack of pseudo cross-sectional image. Not the internal of cross section is authentic, but the edge or contour is valid. Several applications can implicitly take advantages from the stack of contour, for instance, 3D true-colored modelling and geometric measurements. Nevertheless, the process has a problem to extract the highly concave-shape object due to the blind of camera by the occluded patches.
Visualization of dynamic behaviour of multi-agent systems
(UNION Agency, 2004) Řehoř, David; Slavík, Pavel; Kadleček, David; Nahodil, Pavel; Skala, Václav
The extension of our research on analysis of a single agent or agent communities combining advanced methods of visualization with traditional AI techniques is presented in this paper. Even though this approach can be used for arbitrary Multi-Agent System (MAS), it was primarily developed to analyze systems falling into Artificial Life domain. Traditional methods are becoming insufficient as Multi-Agent Systems (MAS) are becoming more complex and therefore novel approaches are needed. In this paper we present an extension of our recent visualization tools suite. The previous approach was not suitable well to present the dynamics of the MAS, even though the development of MAS state parameters in time was presented. Our new technique, which is presented in this paper, addresses this problem by visualizing the changes of the MAS along with their quality and context. This transparent approach emphasizes MAS dynamics by providing means for discovery of changes in its tendencies or in behaviour of either single agent or agent communities. A simulated artificial life environment with intelligent agents has been used as a test bed. We have selected this particular domain because our longterm goal is to model life as it could be so as to understand life, as we know it.
Towards high precission digital elevation model
(UNION Agency, 2004) Ramos, Mª Isabel; Feito, Francisco R.; Gil, Antonio J.; Skala, Václav
In this work, in experimental phase, the digital elevations models (DEMs) appear as a fundamental tool for studying erosion of the land in a concrete zone of agricultural production, olives production. Collected data from the zone of study in different campaigns are used to determine possible variations in the orography of the land. GPS is the used tool to measuring coordinates of points in the land due to the special characteristics of the zone of work. This study is complemented with the analysis of those parameters that influence in the erosion of the olives land: slopes and climatology. A work of these characteristics as much requires of precision and reliability in the stages of taking of data of field like in the phases of treatment and management of the information, so such data will be integrated in a GIS so that it allows to interrelate all data, to modellling them, to interpolate and to extrapolate information as well as the possibility of visualising the possible environmental changes that they take place.
Computer graphics of kinematic surfaces
(UNION Agency, 2004) Rachkovskaya, Galina S.; Kharabayev, Yuriy N.; Rachkovskaya, Natalia S.; Skala, Václav
This work deals with some problems of constructing and graphical displaying for a class of kinematic surfaces generated by mutual moving ruled surfaces touching one another along their common ruling in each position [1,2]. Exactly, we are dealing with the surfaces generated by movement of a cone fixed ruling during combined movement of the cone with respect to a torse surface [2]. The movement is defined as a cone rotating with simultaneous movement of the cone vortex along the torse edge-of-regression so that both surfaces, the torse and the cone, touch one another along the common ruling [3-5]. The methods and program modules developed allow using a wide range of curves as a torse edge-of-regression and a cone guiding line. Since the program modules are implemented using some numerical methods the application of a new-type curve is reduced to define the curve within the program module. This computer implementation includes cylindrical circular and elliptical helixes, and lines based on circular and elliptical helixes as the edge-of-regression, and circle and ellipse curves as the cone guiding line. Surfaces obtained are displayed on a screen in a ‘frame’ (Fig. 1) or ‘solid’ (Fig. 2) style in any user-selected projection.
3D shape recovery with no explicit video projector calibration
(UNION Agency, 2004) Pribanic, Tomislav; Cifrek, Mario; Peharec, Stanislav; Skala, Václav
3D shape reconstruction is a common task in many areas of interests. Yet, very often it involves sophisticated hardware and software. This paper represents cheap and simple system, both in hardware and software sense, for 3D subjects shape reconstruction. It consists of video camera(s) and video projector and is based on well known principle of structured light. A major contribution of the paper is method, which avoids explicit traditional video projector calibration. A system accuracy results are shown along with experimental results of reconstruction for human face and toy mushroom. The system can be easily implemented and adjusted for all kinds of other applications.
Iterative stripification of a triangle mesh: focus on data structures
(UNION Agency, 2004) Porcu, Massimiliano B.; Scateni, Riccardo; Skala, Václav
In this paper we describe the data structure and some implementation details of the tunneling algorithm for generating a set of triangle strips from a mesh of triangles. The algorithm uses a simple topological operation on the dual graph of the mesh, to generate an initial stripification and iteratively rearrange and decrease the number of strips. Our method is a major improvement of a proposed one originally devised for both static and continuous level-of-detail (CLOD) meshes and retains this feature. The usage of a dynamical identification strategy for the strips allows us to drastically reduce the length of the searching paths in the graph needed for the rearrangement and produce loop-free triangle strips without any further controls and post-processing, while requiring a more sophisticated implementation to manage the search and undo operations.
Robot hand visual tracking using an adaptive fuzzy logic controller
(UNION Agency, 2004) Peréz, Carlos; Reinoso, Oscar; Vicente, Asunción M.; Skala, Václav
This paper presents an algorithm to track an industrial robot hand during its movement. Based on acquired image and knowing the robot hand model, the pose is obtained. This information is used to move a pan-tilt camera and keep the robot hand centered in the image every time using an adaptive fuzzy logic controlled. This control law is used combined with a position prediction technique to improve the system behavior. Vision based systems have a lot of empirically adjustable parameters for a good working. With the algorithm proposed in this paper, the adjustable parameters are minimum, so the system robustness is increased.
JaGrLib: library for computer graphics education
(UNION Agency, 2004) Pelikán, Josef; Kostlivý, Jan; Skala, Václav
This article describes JaGrLib – environment for experimenting with algorithms, data structures, general approaches and implementation patterns. This framework was primarily developed to help teaching of computer graphics at Charles University in Prague. But it can be used as a handy tool for experimenting in any branch of applied computer science where modularity, versatility and reusability are key features. The system is implemented in Java language and takes advantage of its object-oriented design, good portability, exibility, etc. At the end of 2003 a new graphical environment was developed and the whole library is publicly available with dozen of modules – mainly from eld of computer graphics.

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