Short Presentations 2006

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https://diglib.eg.org/handle/10.2312/255

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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 Hansen
In 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.
Simulating Drilling on Tetrahedral Meshes
(The Eurographics Association, 2006) Turini, G.; Ganovelli, F.; Montani, C.; Dieter Fellner and Charles Hansen
Bone drilling is a fundamental task in several surgical procedures, including mastoidectomy, cochlear implantation, orbital surgery. It consists in eroding the part of the bone in contact with the tip of the surgical tool when a sufficient pressure is exerted. Since the bone is an almost rigid material, the bone drilling simulations usually employ voxel-based representations of the bone, so that it is easy to show material removal by playing with material density in the voxels. Unfortunately, there are cases in which drilling is only a part of the task, and parts of the same object are also cut away or, worse, the bone is slightly deformable and therefore voxel-based representations do not work well. We propose a novel method to simulate drilling on objects represented explicitly by means of a tetrahedral mesh. The key idea of our method is to create an alternative representation of the tetrahedron when it is partially eroded. Such representation consists of a set of smaller tetrahedra obtained by a hierarchical decomposition of the original one, and combined to represent the current status of the erosion.
Magical Mirrors
(The Eurographics Association, 2006) Michelis, D.; Send, H.; Resatsch, F.; Schildhauer, T.; Dieter Fellner and Charles Hansen
This article describes the multi-media art installation MAGICAL MIRRORS with which the tradition of the mirror, as a medium of visual simulation, is carried over into the world of digital mediums. As theoretical framework, the basic principle of remediation as described by Bolter and Grusin is utilized. According to this theory new media technologies always represent the advancements of prior media that are either enhanced in order to upgrade the features or replaced entirely. MAGICAL MIRRORS follows in the tradition of the magical mirror found in palaces or amusement parks. Like their predecessors they awaken the curiosity of the viewer and invite him or her on a trip into virtual worlds.
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 Hansen
We 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.
Preface and Table of Contents
(The Eurographics Association, 2006) -; Dieter Fellner and Charles Hansen
Preface and Table of Contents
Articulated Video Sprites
(The Eurographics Association, 2006) Vanaken, C.; Gerrits, M.; Bekaert, P.; Dieter Fellner and Charles Hansen
In 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.
SpringLens Distributed Nonlinear Magnifications
(The Eurographics Association, 2006) Germer, T.; Götzelmann, T.; Spindler, M.; Strothotte, Th.; Dieter Fellner and Charles Hansen
We present a flexible, distributed and effective technique to model custom distortions of images. The main idea is to use a mass-spring model to create a flexible surface and to create distortions by changing the rest-lengths. A physical simulation works out the displacements of this particle grid. We provide intuitive tools to interactively design such nonlinear magnifications. In addition, our system enables data-driven distortions which allows us to use it for automatic nonlinear magnifications. We demonstrate this with an application for labeling of 3D scenes.
Evaluation of Different Diffuse Surface Reflection Models for Global Illumination
(The Eurographics Association, 2006) Diepstraten, Joachim; Borgo, Rita; Dieter Fellner and Charles Hansen
One common goal nearly all global illumination algorithms aim for is solving the light transport problem. The most visual noticeable one in the general case is the diffuse-diffuse light transport between surfaces. Most global illumination algorithms are very good at solving it. In many global illumination solutions the Lambertian diffuse surface reflection model is assumed. However, over the years several other diffuse models have been introduced mostly outside of the computer graphics community that according to their authors mimic real surface behaviour more accurately. In this paper we evaluate some of the better known models and place them into the context of solving global illumination problems.
Rapid Modeling of Complex Building Façades
(The Eurographics Association, 2006) Finkenzeller, D.; Schmitt, A.; Dieter Fellner and Charles Hansen
Architectural settings occur in many virtual environments. Modeling such highly detailed structures manually is a time-consuming and tedious task. Therefore we propose a system for the rapid modeling of building façades. The designer just has to provide some coarse information, the building outline, its type and style and the computer takes care of creating the exact geometry. Adjacent architectural structures are adapted automatically, e. g. walls are adapted to exactly fit quoins made of different stone blocks. Also highly detailed façade elements like window frames made of single bricks, cornices, etc. are generated. Even at this point the designer can still interfere and change the building outline, the style, as well as window or door frame styles. Such a tool will relieve the designer of the burden of tedious, recurring and over all time-consuming modeling tasks.
Virtual See-through Displays: Interactive Visualization Method in Ubiquitous Computing Environments
(The Eurographics Association, 2006) Shin, Seonhyung; Lee, Gun A.; Yang, Ungyeon; Son, Wookho; Dieter Fellner and Charles Hansen
Cooperation between multiple information devices is necessary in ubiquitous computing environments. Consequently, visual display interfaces also need to cooperate with each other to help users to understand virtual information in a consistent way. In this point of view, we propose a concept of 'virtual seethrough' visualization which supports not only context consistency between multiple visual displays, but also supports personalized and quality supplemented visualizations. We also describe various interaction methods available with virtual see-through displays. By adding information and participant management, we expect 'virtual see-through' will be one of the popular visualization methods for visual display interfaces in ubiquitous computing environments.
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 Hansen
A 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.
GPU-Based Hierarchical Texture Decompression
(The Eurographics Association, 2006) Stachera, J.; Rokita, P.; Dieter Fellner and Charles Hansen
We 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.
Fast Skeletal Animation by skinned Arc-Spline based Deformation
(The Eurographics Association, 2006) Forstmann, Sven; Ohya, Jun; Dieter Fellner and Charles Hansen
Presented is a novel skeletal animation system for providing high quality geometric deformations in real-time. Each bone of the skeleton is therefore represented by a spline, rather than using conventional matrix rotation. In our approach, each vertex of the animated character can be influenced by a maximum of three spline-curves, which is sufficient for skinned animation. One spline is parameterized by three control points and a possible twist. As opposed to conventional Bézier curves does our arc-spline rely on trigonometric functions for providing better curvatures. The optimized implementation using the OpenGL-shading language shows very promising results for real-time character animation, as even about 1 Million vertices were able to be transformed at interactive 43 frames per second on a GeForce 7800 GTX graphics card.
Enhanced Cartoon and Comic Rendering
(The Eurographics Association, 2006) Spindler, Martin; Röber, Niklas; Döhring, Robert; Masuch, Maic; Dieter Fellner and Charles Hansen
In 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.
Modeling Real-time Rendering
(The Eurographics Association, 2006) Wong, Chee-Kien Gabriyel; Wang, Jianliang; Dieter Fellner and Charles Hansen
The 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.
Multiresolution GPU Mesh Painting
(The Eurographics Association, 2006) Ritschel, Tobias; Botsch, Mario; Müller, Stefan; Dieter Fellner and Charles Hansen
Mesh painting is a well accepted and very intuitive metaphor for adding high-resolution detail to a given 3D model: Using a brush interface, the designer simply paints fine-scale texture or geometry information onto the surface. In this paper we propose a fully GPU-accelerated mesh painting technique, which provides real-time feedback even for highly complex meshes. Our method can handle arbitrary input meshes, which are considered as base meshes for Catmull-Clark subdivision. Representing the surface by an atlas of geometry images and exploiting programmable vertex and fragment shaders allows for highly efficient LoD rendering and surface manipulation. Our painting metaphor supports real-time texturing, sculpting, smoothing, and multiresolution surface deformations.
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 Hansen
This 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.
Digital HPO Hologram Rendering Pipeline
(The Eurographics Association, 2006) Janda, M.; Hanák, I.; Skala, V.; Dieter Fellner and Charles Hansen
This 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.
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 Hansen
Ultimately, 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.
Elastic Facial Caricature Warping
(The Eurographics Association, 2006) Clarke, Lyndsey; Chen, Min; Townsend, Peter; Mora, Benjamin; Dieter Fellner and Charles Hansen
Caricatures are usually created by skilled artists, and, due to their amusing appearance, they serve mainly as a source of entertainment and humour. This short paper is therefore concerned with a means for generating facial caricatures from given photographs using image warping. In particular, we propose to assign virtual physical and material properties to various facial features in order to specify and render exaggerated transformations in an intuitive manner. Though our objective is not for creating physically accurate photorealism, our physically-based approach enables users to associate virtual displacements in caricatures, with common physical phenomena.

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