EG2006
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Item Interactive Volume Rendering with Ray Tracing(The Eurographics Association, 2006) Marmitt, Gerd; Friedrich, Heiko; Slusallek, Philipp; Brian Wyvill and Alexander WilkieRecent research on high-performance ray tracing has achieved real-time performance even for highly complex surface models already on a single PC. In this report we provide an overview of techniques for extending real-time ray tracing also to interactive volume rendering. We review fast rendering techniques for different volume representations and rendering modes in a variety of computing environments. The physically-based rendering approach of ray tracing enables high image quality and allows for easily mixing surface, volume, and other primitives in a scene, while fully accounting for all of their optical interactions. We present optimized implementations and discuss the use of upcoming high-performance processors for volume ray tracing.Item Two Layer Image Tile Mosaics(The Eurographics Association, 2006) Kang, Dongwann; Park, Young-Sup; Seo, Sang-Hyun; Yoon, Kyung-Hyun; Dieter Fellner and Charles HansenThis study proposes a method of Two Layer Image Tile Mosaics to preserve detailed depiction of the source image. This method is composed of following three stages. First of all, the upper layer tile is located through a centroidal Voronoi diagram to which an edge avoidance technique is applied, and the position of the lower layer tile is calculated using Delaunay triangulation. Secondly, discover the size and direction field of the tile considering the relation between tiles. Thirdly, adopt a Photomosaics technique to use the image tiles. At this time, the technique of multi-level indexing is used to accelerate the speed of image searching. The Two Layer Image Tile Mosaics obtained through the above process preserve the detailed depiction of source images effectively.Item Articulated Video Sprites(The Eurographics Association, 2006) Vanaken, C.; Gerrits, M.; Bekaert, P.; Dieter Fellner and Charles HansenIn this paper, we present an extension to video sprites for articulated characters. Central to our technique is a matching cost which works on high-level 2D skeletal representations of the characters, instead of their visual appearance. Through a combination of different heuristics, we are able to animate a character according to a new sequence of target skeletons. This way we achieve an accurate matching and a hitherto unseen level of control over the video sprite.Item Evaluation Test for 3D Computer Graphics Content Production Capability based on Simulation Methodology(The Eurographics Association, 2006) Miyai, Ayumi; Nakamura, Tagiru; Mikami, Koji; Kawashima, Motonobu; Yamaguchi, Yasushi; Judy Brown and Werner HansmannThrough 15 years experience with the Certification Test of Computer Graphics by the Computer Graphic Arts Society, we have felt importance of a new style of test, namely simulation test (ST). The goal of ST is to evaluate the examinees knowledge and skills using simulation methodology. We conducted an experimental test session of ST in November 2005. In this experimental session, we also conducted a Paper and Pencil Test (PPT) for comparison. An assignment is shown to 75 testees by a storyboard. The testees read the storyboard, then, create answer work using ST software which we developed for this session. The testees would select and deploy characters, props, lights, and cameras, all of which has prepared to set parameters for the position, degree, focal length and etc. according to the timeline. The evaluation was conducted to check whether the testees' answer work is matched to the correct answer work. We analyzed results of both ST and PPT. We especially focused on the score difference and progress difference due to the level of proficiency of our testees operating ST software, and the correlation between their learning experiences and score, and on correlation between ST and PPT scores. From the results, we confirmed that the correlation between the scores of both ST and PPT was observed among all the testees, and that the scores of ST show the possibility of evaluating accumulation of skills of the testees to be able to brush up creativity for moving image content production with 3D computer graphics.Item Exploring Flow Fields with GPU-Based Stream Tracers in Virtual Environments(The Eurographics Association, 2006) Schirski, Marc; Bischof, Christian; Kuhlen, Torsten; Dieter Fellner and Charles HansenIn this paper we present an immersive visualization approach for the intuitive exploration of flow fields, which operates entirely within the graphics subsystem. We augment particle data with a brief history of their recent positions, thus effectively computing and displaying animated tracers facilitating the understanding of the underlying flow field. Image quality is enhanced by employing a billboard-based rendering method for the particle trajectories simulating lit tubular geometry. This leads to significantly reduced depth perception problems and depth order ambiguities. Interactivity is maintained even for large amounts of tracers by shifting the computational load to the GPU. We alleviate 3D seed point specification problems by offering interaction mechanisms with full 6 degrees-of-freedom within an immersive virtual environment.Item Connectivity-Aware Sectional Visualization of 3D DTI Volumes using Perceptual Flat-Torus Coloring and Edge Rendering(The Eurographics Association, 2006) Demiralp, Çagatay; Zhang, Song; Tate, David F.; Correia, Stephen; Laidlaw, David H.; Dieter Fellner and Charles HansenWe present two new methods for visualizing cross-sections of 3D diffusion tensor magnetic resonance imaging (DTI) volumes. For each of the methods we show examples of visualizations of the corpus callosum in the midsagittal plane of several normal volunteers. In both methods, we start from points sampled on a regular grid on the cross-section and, from each point, generate integral curves in both directions following the principal eigenvector of the underlying diffusion tensor field.We compute an anatomically motivated pairwise distance measure between each pair of integral curves and assemble the measures to create a distance matrix. We next find a set of points in a plane that best preserves the calculated distances that are small each point in this plane represents one of the original integral curves. Our first visualization method wraps this planar representation onto a flat-torus and then projects that torus into a visible portion of a perceptually uniform color space (L*a*b*). The colors for the paths are used to color the corresponding grid points on the original cross-section. The resulting image shows larger changes in color where neighboring integral curves differ more. Our second visualization method lays out the grid points on the cross section and connects the neighboring points with edges that are rendered according to the distances between curves generated from these points. Both methods provide a way to visually segment 2D cross sections of DTI data. Also, a particular contribution of the coloring technique used in our first visualization method is to give a continuous 2D color mapping that provides approximate perceptual uniformity and can be repeated an arbitrary number of times in both directions to increase sensitivity.Item Real Time Interactive Massive Model Visualization(The Eurographics Association, 2006) Kasik, D.; Manocha, D.; Stephens, A.; Bruderlin, B.; Slusallek, P.; Gobbetti, E.; Correa, W.; Quilez, I.; Nadia Magnenat-Thalmann and Katja BühlerReal-time interaction with complex models has always challenged interactive computer graphics. Such models can easily contain gigabytes of data. This tutorial covers state-of- the-art techniques that remove current memory and performance constraints. This allows a fundamental change in visualization systems: users can interact with huge models in real time.Item Preface and Table of Contents(The Eurographics Association, 2006) -; Dieter Fellner and Charles HansenPreface and Table of ContentsItem Shape From Silhouette: Towards a Solution for Partial Visibility Problem(The Eurographics Association, 2006) Michoud, B.; Guillou, E.; Bouakaz, S.; Dieter Fellner and Charles HansenAcquiring human shape is a prerequisite to many applications in augmented and virtual reality, as well as in computer graphics and animation. The acquisition of a real person must be precise enough to have the best possible (realistic) rendering. To do so in real time, "Shape-from-silhouette" (SFS) methods are used. One limitation of these methods is that the acquired subject must be visible from all the camera filming it. If not, some parts of the object are not reconstructed in 3d. This paper presents a modified SFS algorithm, that extends the 3d reconstruction space. Our extension allows to build an estimation of an object s 3d shape even if it comes out of sight from one or more cameras.Item Automatic Depth-Map Colorization(The Eurographics Association, 2006) Hassner, T.; Basri, R.; Dieter Fellner and Charles HansenWe present a system for automatically generating custom, structured image-maps for input depth-maps. Our system thus allows quick fitting of masses of objects with tailor-made image-maps. Given a depth-map of a novel 3D object, our method tiles it with intensities from similar, pre-collected, textured objects. These are seamlessly merged to form the new image-map. This process is performed by optimizing a well defined target likelihood function, via a hard-EM procedure. We present results for varied object classes including human figures, and fish.Item High Performance Virtual Garment Simulation(The Eurographics Association, 2006) Straßer, W.; Wacker, M.; Nadia Magnenat-Thalmann and Katja BühlerFor virtual characters the simulation of garments is a vital component towards realistic and believable scenarios that range from interactive virtual reality (virtual tailoring and cultural heritage) to realistic synthetic animation (CAD modeling and film production). This course addresses the key techniques involved in the latest state-of-theart in physically based cloth simulation.Item Using VTK as a Tool for Teaching and Applying Computer Graphics(The Eurographics Association, 2006) Dias, Paulo; Madeira, Joaquim; Santos, Beatriz Sousa; Judy Brown and Werner HansmannDuring the first semester of 2005/2006 we used the Visualization Toolkit (VTK) as a tool for teaching and applying Computer Graphics, both for Computer Engineering students who chose to attend the 3D Modeling and Visualization course, and for M.Sc. students specializing in Computer Graphics. In both cases, students had not only to use VTK in about half of their lab classes, in order to accomplish some tasks and gain some knowledge on VTK s features and functionalities, but they were also required to develop a visualization application based on VTK. We describe first the motivation for using VTK in these two different scenarios, as well as the main course topics where we used the toolkit. Afterwards, we present some of the most successful projects developed by our students. Finally, we state some conclusions.Item Real-time Reflection using Ray Tracing with Geometry Field(The Eurographics Association, 2006) Li, Shengying; Fan, Zhe; Yin, Xiaotian; Mueller, Klaus; Kaufman, Arie E.; Gu, Xianfeng; Dieter Fellner and Charles HansenA novel method for accurate reflections in real time is introduced using ray tracing in geometry fields, which combine light fields with geometry images. The geometry field of a surface is defined ray space, mapping a ray to its intersection point with the surface, represented as the uv coordinates on the geometry image. It makes intersection tests much more efficient using lookups within a fragment shader, and allows conventional textures to be applied, such as normal maps, to enhance geometric subtleties. Our method can be generalized to also handle refraction and self-reflection. Experimental results demonstrate its capability for accurate reflection for complex scenes in real-time.Item Digital HPO Hologram Rendering Pipeline(The Eurographics Association, 2006) Janda, M.; Hanák, I.; Skala, V.; Dieter Fellner and Charles HansenThis paper describes a rendering pipeline for digital hologram synthesis. The pipeline is capable of handling triangle meshes, directional light sources, texture coordinates, and advanced illumination models. Due to the huge computational requirements of hologram synthesis only the HPO holograms are considered.Item Toward the Light Field Display: Autostereoscopic Rendering via a Cluster of Projectors(The Eurographics Association, 2006) Yang, Ruigang; Huang, Xinyu; Li, Sifang; Jaynes, Christopher; Dieter Fellner and Charles HansenUltimately, a display device should be capable of reproducing the visual effects that are produced by reality. In this paper we introduce an autostereoscopic display that uses a scalable array of digital light projectors and a projection screen augmented with microlenses to simulate a light field for a given three-dimensional scene. Physical objects emit or reflect light in all directions to create a light field that can be approximated by the light field display. The display can simultaneously provide many viewers from different viewpoints a stereoscopic effect without head-tracking or special mechanical devices. We present a solution to automatically calibrate the light field display and an efficient algorithm to render the special multi-view images it requires by exploiting their spatial coherence. The effectiveness of our approach is demonstrated with a four-projector prototype that can display dynamic imagery with full parallax.Item Enhanced Cartoon and Comic Rendering(The Eurographics Association, 2006) Spindler, Martin; Röber, Niklas; Döhring, Robert; Masuch, Maic; Dieter Fellner and Charles HansenIn this work we present an extension to common cel shading techniques, and describe four new cartoon-like rendering styles applicable for real-time implementations: stylistic shadows, double contour lines, soft cel shading, and pseudo edges. Our work was mainly motivated by the rich set of stylistic elements and expressional possibilities within the medium comic. In particular, we were inspired by Miller s Sin City and McFarlane s Spawn . We designed algorithms for these styles, developed a real-time implementation and integrated it into a regular 3D game engine.Item Modeling Real-time Rendering(The Eurographics Association, 2006) Wong, Chee-Kien Gabriyel; Wang, Jianliang; Dieter Fellner and Charles HansenThe real-time rendering process is well known to be extremely dynamic and complex. This paper presents a novel approach to modeling this process via the system identification methodology. Given the process s dynamic nature arising from the possible myriad variations of render states, polygon streams and the non-linearities involved, we describe a modeling approach using neural networks with supervised training from application-generated data. By comparing the outputs of the neural network model s representation of the rendering process with actual empirical data, we discuss the accuracy of our approach in relation to the practical issues of integrating this study to real-world applications.Item GPU-Based Hierarchical Texture Decompression(The Eurographics Association, 2006) Stachera, J.; Rokita, P.; Dieter Fellner and Charles HansenWe propose a hierarchical texture compression algorithm for real-time decompression on the GPU. Our algorithm is characterized by low computational complexity, random access and hierarchical structure which allow us to access first three levels of encoded mip-map pyramid. The hierarchical texture compression algorithm HiTCg is based on block-wise approach, where each block is subject to local fractal transform.Item Graphics-Based Learning in First-Year Computer Science(The Eurographics Association, 2006) Davis, Timothy A.; Judy Brown and Werner HansmannThis paper proposes a method for teaching a first-year course in computer science using graphicsbased problems as the teaching medium. Specifically, we present a method for instruction in programming using a semester-long project of developing a ray tracer. This effort is part of a larger project, in which a broad range of undergraduate courses are taught using computer graphics as the motivating application. An overview of this project is provided, along with description and results from the first trial CS2 course instructed using this technique.Item Lighting-Up Geometry: Accurate 3D Modelling of Museum Artifacts with a Torch and a Camera(The Eurographics Association, 2006) Vogiatzis, G.; Hernández, C.; Cipolla, R.; Dieter Fellner and Charles HansenThis paper addresses the problem of obtaining complete, very detailed reconstructions of shiny objects such as glazed ceramics. We present an algorithm which uses silhouettes of the object, as well as images obtained under changing illumination conditions. In contrast with previous photometric stereo techniques, ours is not limited to a single viewpoint but produces accurate reconstructions in full 3D. A number of images of the object are obtained from multiple viewpoints, under varying lighting conditions. Starting from the silhouettes, the algorithm recovers camera motion and constructs the object s visual hull. This is then used to recover the illumination and initialise a multi-view photometric stereo scheme to obtain a closed surface reconstruction. The algorithm has been implemented as a practical model acquisition system. Here, we present a number of complete reconstructions of challenging real objects.