WSCG '2001: Conference proceedings

Permanent URI for this collection

http://hdl.handle.net/11025/11243

1 článek (Zakaria, M. N. Interactive evolutionary approach to character animation) nebyl uložen s ohledem na poškozený soubor.

Browse

Showing 1 - 20 out of 57 results

A Multichannel Variational Model for Robust Image Segmentation under Noise
(University of West Bohemia, 2001) Romano, R.; Vitulano, D.; Skala, Václav
This paper presents a novel model for image segmentation under noise: EVRIST (Efficient Variational Representation for Image Segmentation Technique). In order to segment general images containing both quite smooth regions and textures, EVRIST, based on a hierarchical representation obtained by the classical weak membrane, utilizes two channels: one relative to the mean and another for the edges density. The results achieved on both manual compositions and on real images, show the high robustness to the noise along with a low computational effort.
Volume Visualization: Technology to Tools
(University of West Bohemia, 2001) Nadeau, David R.; Skala, Václav
Every new technology travels a path from excitement to application. At first we are excited and amazed by the technology."How is this done?", we ask. We study it and experiment with it, and try to impress our friends by explaining to them how it works. Later, as the technology matures, we begin instead to ask "How is this useful?". It is no longer important how it works, but rather how it helps in real applications. The technology becomes a tool. This path has been taken many times. Perhaps you recall when word processing first arrived? We all played with fonts and styles and used as many as we could in one document. Today, the technology is mature and even boring. It is now a tool. Or perhaps you recall the birth of spreadsheets, painting programs, or simple PC databases? Or, more recently, the arrival of interactive 3D on the PC, or the use of image based rendering tricks in the special effects for "The Matrix" movie. Each of these technologies splashed onto the scene, amazed us, and now are slowly maturing to tool status. In this talk, I will speculate on where volume visualization is now on this path from technology to tool. I will discuss some of the advancements still needed, and give examples on current real uses for volume visualization. I will highlight recent work at the San Diego Supercomputer Center where we are using volume visualization to explore the enormous structure of the Orion Nebula, examine the microstructure of cancer cells, and study changes in temperature in the world's oceans.
Using Vision for Animating Virtual Humans
(University of West Bohemia, 2001) Kakadiaris, Ioannis A.; Skala, Václav
Automatic, non-intrusive vision-based capture of the human body motion opens new possibilities in applications requiring the use of geometric and kinematic data from individuals (e. g., virtual reality, performance measurement). If synthesized motion is to be compelling, we must create actors for computer animations and virtual environments that appear when they move. In this talk, I will present the computer vision and computer graphics formulations and techniques that we have developed for the three-dimensional model-based motion capture and animation of unconstrained human movement from multiple cameras. Our tracking and animation system consists of a human motion analysis and a synthesis components. First, I will present novel analytical computer vision techniques to accurately recover the three-dimensional shape and pose of a subject's body parts. These techniques are based on the spatio-temporal analysis of a subject's silhoutte from image sequences acquired simultaneously from multiple cameras. We employ physics-based deformable human body models to estimate the position and orientation of the subject's body parts during the analysis steps. This amounts to minimizing continously the discrepancy between the occluding contour of the deformable model and the silhoutte of the human in the acquired image sequences. To mitigate difficulties arising due to occlusion, we employ multiple cameras. For efficiency and robustness, we have devised two criteria for the active time-varying selection of the subset of the cameras that provide the most information. These criteria depend on the visibility of the subject's body parts and the observability of their predicted motion from the specific camera. For the motion synthesis component, we have developed techniques that allow the efficient and realistic animation of the subject's estimated graphical model. The advantage of our system is that the subject does not have to wear markers or special equipment. Finally, I will present motion estimation and animation results demonstrating the generality and robustness of our algorithm.
Enhancement to Directional Coherence Maps
(University of West Bohemia, 2001) Scheel, Annette; Stamminger, Marc; Pütz, Jörg; Seidel, Hans-Peter; Skala, Václav
Directional Coherence Maps as proposed by Guo in ’98 are a very efficient acceleration technique for ray tracing based global illumination renderers. It vastly reduces the number of pixels which have to be computed exactly by identifying regions which are suitable for interpolation. By using oriented finite elements for interpolation, the sampling density can be kept low for large regions of the target image. In this paper we describe extensions of the method. An improved object test is presented which prevents that small objects are missed. Additionally, it is shown how to handle textures efficiently, which was not possible with the original approach.
Testing Monte-Carlo Global Illumination Methods with Analytically Computable Scenes
(University of West Bohemia, 2001) Szirmay-Kalos, László; Kovács, László; Abbas, Ali Mohamed; Skala, Václav
The paper presents analytically computable scenes for testing global illumination algo-rithms with arbitrary BRDFs. The task of these scenes is to enable us to compare global illumination algorithms and check the correctness of the implementation. In our first ap-proach a criterion is given that makes the radiance constant for an arbitrary closed scene allowing either arbitrary BRDFs or arbitrary lightsource models. In the second approach the geometry is assumed to be an internal surface of a sphere. Here homogeneous diffuse and mirror like reflections can be tested with arbitrary lightsource models.
Progressive Light Path Building
(University of West Bohemia, 2001) Szirmay-Kalos, Lászlo; Antal, György; Sbert, Mateu; Skala, Václav
The paper proposes a global illumination method that builds up the light paths progres-sively taking into account all relevant previous information. The basis of the method is a self-correcting stochastic iteration scheme, which works with a population of photon hits. In each iteration step a ray is generated randomly either from a light source or by reflect-ing an earlier hit, then the ray is traced to obtain a new hit. In order to limit the size of the hit population, hits are decimated randomly after certain iteration steps. Comparing the new approach to random walk techniques, this method can reuse the illumination and visibility information gathered with previous rays. By defining the decimation strategy properly, the view-importance can be built into the algorithm.
Synthetic Images of Underwater Scenes: A First Approximation
(University of West Bohemia, 2001) Cerezo, E.; Serón, F. J.; Skala, Václav
The creation and rendering of realistic water scenes is one of the challenging tasks in Computer Graphics. To reproduce the illumination and colour inside water bodies an algorithm capable of dealing with media with anisotropic and multiple scattering has to be used. We have chosen the discrete ordinates method to solve the problem of light transport. Both the theoretical basis and the algorithm that has been implemented are described in the paper. A couple of simple images calculated in different waters are presented. Results indicate the relevant role played by the spectral behaviour of the absorption and scattering coefficients in the process of image generation.
Computer-Generated Chinese Painting for Landscapes and Portraits
(University of West Bohemia, 2001) Way, Der-Loy; Hsu, Chih-Wei; Chiu, Hsin-Yi; Shih, Zen-Chung; Skala, Václav
Practiced for more than three thousand years, Chinese painting stresses the notion of "implicit meaning" in which painters use a minimum amount of strokes to express their deepest feelings. Chinese landscape and figure paintings are the two major themes of Chinese painting. Of relevant interest is more thoroughly understand Chinese art by analyzing basic rules of Chinese painting. This paper proposes two novel methods capable of synthesizing rock textures in Chinese landscape painting and synthesizing portraits in Chinese figure painting, respectively. In addition to saving time during trial and error, these two methods attempt to synthesize painting styles. After users only specify the contour and parameters, our methods underwrite the complete painting process. With the requirement of familiarity with painting skills, individuals can paint various styles of Chinese painting.
The Magic of the Z-Buffer: A Survey
(University of West Bohemia, 2001) Theoharis, Theoharis; Papaioannou, Georgios; Karabassi, Evaggelia-Aggeliki; Skala, Václav
The wide availability of hardwired Z-buffer has sparked an explosion in the number of applications of the algorithm whose origins lie in hidden surface elimination. This paper presents a much-needed survey of key applications of the Z-buffer from the fields of rendering, modelling and vision in a common notation in order to help users make better use of this resource.
Toward the Effective Animation of American Sign Language
(University of West Bohemia, 2001) Sedgwick, Eric; Alkoby, Karen; Davidson, Mary Jo; Roymieco, Carter; Juliet, Christopher; Craft, Brock; Furst, Jacob; Hinkle, Damien; Konie, Brian; Lancaster, Glenn; Luecking, Steve; Morris, Ashley; McDonald, John; Tomuro, Noriko; Toro, Jorge; Wolfe, Rosalee; Skala, Václav
American Sign Language (ASL) is the primary language used by the North American Deaf Community. We present our method for producing natural animations of fingerspelling, a functionally important subset of ASL. User testing demonstrates that our animations are readily identified by members of the deaf community.
Interaction Approach for Digital Based Storytelling
(University of West Bohemia, 2001) Braun, Norbert; Skala, Václav
This paper shows an approach for a storytelling oriented interaction on digital video. All the interaction capabilities of the system are driven by the video context and therefore media centric. Interaction possibilities are given to the audience by conversation (on topics of the video content) or by classical Direct Manipulation (of video objects). Conversations can be done by the user with a personalized assistance or directly with the video. The implementation of the approach is shown by a discussion about an application architecture on the basis of Real Media Server, SMIL and Java 3D. The application runs as a Video On Demand system, accessible through the world wide web.
Towards Interactivity on Texturing Implicit Surfaces: A Distributed Approach
(University of West Bohemia, 2001) Zonenschein, R.; Gomes, J.; Velho, L.; Rodriguez, N.; Skala, Václav
We describe a distributed system for texture mapping implicit surfaces. The method uses a particle system associated with the gradient vector field of the function that defines an implicit surface to acquire texture coordinates at a support surface. As each particle trajectory is independent of each other, this method has a special suitability to run in parallel. Our results show good improvement as more processors are added to the system, with speedups of up to 13 with 32 processors, performance such as required by an interactive system.
Visibility Complexity of Animation in Flatland
(University of West Bohemia, 2001) Rigau, Jaume; Feixas, Miquel; Sbert, Mateu; Skala, Václav
In this paper we address the problem of measuring the visibility complexity of scene animation in flatland. In our previous work we proposed a complexity mea-sure which quantifies the information transfer in a static scene. Here we introduce two measures to capture the complexity of movement. The first approach measures the dissimilarity between successive frames of an animation using the variation of information exchange between each pair of patches. The second one is the eu-clidean distance between form factor distributions. We present preliminary results which show that both approaches attain a satisfactory and very similar animation classification.
Parallel Implementation of Stochastic Iteration Algorithms
(University of West Bohemia, 2001) Martínez, Roel; Szirmay-Kalos, László; Sbert, Mateu; Abbas, Ali Mohamed; Skala, Václav
The paper examines the parallel implementation of iteration type global illumination al-gorithms. The steps of iteration depend on each other, thus their parallel implementation is not as straightforward as for random walks. This paper solves the interdependency problem by applying stochastic iteration. In this framework two fundamental questions are investigated: how many processors can be efficiently used in an algorithm and how often the processors should exchange their information. These questions are answered by a theoretical model and also by simulations.
Anti-aliased Hemicubes for Performance Improvements in Radiosity Solutions
(University of West Bohemia, 2001) Kiran, Naga; Mudur, S. P.; Chandran, Sharat; Dalvi, Nilesh; Skala, Václav
Several important and fascinating aspects of realistic images are captured by the radiosity method. In this paper we use an alternate form of the classical hemicube that reduces aliasing problems inherent in the original method without giving up the computational advantages of the hemicube. Unlike other methods, we explicitly consider the e ect of the relative order of partial visibility in a hemicube cell when recording form factors. This enables us to compute form factors accurately (even) in progressive re nement radiosity with adaptive substructuring. Our empirical results with progressive re nement radiosity show superior mesh density where ne details are required, (such as in soft shadows), as well as in areas that produce singularities (such as when inter element distances tend to zero). Our method is contrasted with hierarchical radiosity which uses raycasting for form factor and visibility computations. On a low end Intel Linux platform, and for a comparable image quality, our method takes substantially less time.
Automatic and Continuous Projector Display Surface Estimation Using Everyday Imagery
(University of West Bohemia, 2001) Yang, Ruigang; Welch, Greg; Skala, Václav
Projector-based display systems have been used in computer graphics for about as long as the field has existed. While projector-based systems have many advantages, a significant disadvantage is the need to obtain and then adhere to an accurate analytical model of the mechanical setup, including the external parameters of the projectors, and an estimate of the display surface geometry. We introduce a new method for the latter—for continuous display surface autocalibration . Using a camera that observes the display surface, we match image features in whatever imagery is being projected, with the corresponding features that appear on the display surface, to continually refine an estimate for the display surface geometry. In effect we enjoy the high signal-to-noise ratio of "structured" light (without getting to choose the structure) and the unobtrusive nature of passive correlation-based methods. The approach is robust and accurate, and can be realized with commercial off-the-shelf components. The method can be used with a variety of projector-based displays, for scientific visualization, trade shows, entertainment, tele-immersion, or the Office of the Future. And although we do not demonstrate it in this paper, we have also been working on extending the method to include continual estimation of other system parameters that vary over time.
Image Edge Detection in a Mimic Spiral Architecture
(University of West Bohemia, 2001) Wu, Quiang; Hintz, Tom; He, Xiangjian; Skala, Václav
Detection of edge points of 3-dimensional physical objects in a 2-dimensional image is one of the main research areas of computer vision. Object contour detection and object recognition rely heavily on edge detection. In this paper, we present an edge detection scheme using Gaussian Multi-resolution Theory based on a mimic Spiral Architecture. The Spiral Architecture has been described in many papers. Although it has many ad-vantages such as powerful computational features in image processing especially in image edge detection, there is no available image capture device yet to support this structure. Hence, we mimic the Spiral Architecture from the existing image structure. This mimic structure inherits all computational features of the Spiral Architecture. The Gaussian Multi-resolution Theory is used to reduce noise and unnecessary details of the image.
A Separate Least Squares Algorithm for Efficient Arithmetic Coding in Lossless Image Compression
(University of West Bohemia, 2001) Triantafyllidis, G. A.; Strintzis, M. G.; Skala, Václav
The overall performance of discrete wavelet transforms for lossless image compression may be further improved by properly designing efficient entropy coders. In this paper a novel technique is proposed for the implementation of context-based adaptive arith-metic entropy coding. It is based on the prediction of the value of the current transform coefficient. The proposed algorithm employs a weighted least squares method applied separately for the HH, HL and LH bands of each level of the multiresolution structure, in order to achieve appropriate context selection for arithmetic coding. Experimental re-sults illustrate and evaluate the performance of the proposed technique for lossless image compression.
Geometric Processing of Volumetric Objects
(University of West Bohemia, 2001) Silva, Romildo; Gomes, Jonas; Mota, Cicero; Skala, Václav
This paper introduces techniques of Riemannian for processing and visualising volumetric graphical objects. A family of non-linear high-pass filters, based on curvature tensor, is introduced and used to study the local redundancy on objects. It is shown how to reconstruct an object from geometric non-redundant regions and applications are presented and discussed.
Variable Resolution Level-of-Detail of Multiresolution Ordered Meshes
(University of West Bohemia, 2001) Ribelles, J.; López, A.; Belmonte, O.; Remolar, I.; Chover, M.; Skala, Václav
Variable resolution level-of-detail is an important application of multiresolution modeling, since to use of different resolutions across the surface allows interactive visualization of highly detailed objects. Multiresolution Ordered Meshes (MOM) was first introduced as a model that achieves the efficient management of an ample range of uniform resolution levels-of-detail and presents reduced storage space requirements. In this paper, we introduce an algorithm capable of retrieving variable resolution levels-of-detail from a multiresolution MOM representation without having to reorganize data in new structures or store new information. The proposed algorithm starts from the level of highest detail and simplifies it adaptively to reach the required resolution in each area of the surface. Experiments with data sets of varying complexity demonstrate that the new algorithm obtains variable resolution levels of detail while retaining the advantages of MOMJ.

Browse

Recent Submissions