EG2010

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https://diglib.eg.org/handle/10.2312/277

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3D Isocontours Real-time Generation and Visualization of 3D Stepped Terrain Models
(The Eurographics Association, 2010) Glander, Tassilo; Trapp, Matthias; Döllner, Jürgen; H. P. A. Lensch and S. Seipel
Isocontours (also isopleths, isolines, level sets) are commonly used to visualize real-valued data defined over a 2D plane according to a set of given isovalues. To support the 3D landscape metaphor for information visualization, a 3D stepped terrain can be derived by lifting and extruding isolines to their particular isovalue, but typically requires triangulation of the resulting surface representation in a preprocessing step. We present a concept and rendering technique for triangle-based terrain models that provide interactive, adaptive generation and visualization of such stepped terrains without preprocessing. Our fully hardware-accelerated rendering technique creates additional step geometry for each triangle intersecting an iso-plane on-the-fly. Further, an additional interpolation schema facilitates smooth transition between established 3D terrain visualization and its stepped variant.
Accelerated Deterministic Simulation of X-ray Attenuation Using Graphics Hardware
(The Eurographics Association, 2010) Vidal, Franck; Garnier, M.; Freud, N.; Létang, J.M.; John, N.W.; Anders Hast and Ivan Viola
In this paper, we propose a deterministic simulation of X-ray transmission imaging on graphics hardware. Only the directly transmitted photons are simulated, using the Beer-Lambert law. Our previous attempt to simulate Xray attenuation from polygon meshes utilising the GPU showed significant increase of performance, with respect to a validated software implementation, without loss of accuracy. However, the simulations were restricted to monochromatic X-rays and finite point sources. We present here an extension to our method to perform physically more realistic simulations by taking into account polychromatic X-rays and focal spots causing blur.
Ad-Hoc Multi-Displays for Mobile Interactive Applications
(The Eurographics Association, 2010) Schmitz, Arne; Li, Ming; Schönefeld, Volker; Kobbelt, Leif; Matthew Cooper and Kari Pulli
We present a framework which enables the combination of different mobile devices into one multi-display such that visual content can be shown on a larger area consisting, e.g., of several mobile phones placed arbitrarily on the table. Our system allows the user to perform multi-touch interaction metaphors, even across different devices, and it guarantees the proper synchronization of the individual displays with low latency. Hence from the user s perspective the heterogeneous collection of mobile devices acts like one single display and input device. From the system perspective the major technical and algorithmic challenges lie in the co-calibration of the individual displays and in the low latency synchronization and communication of user events. For the calibration we estimate the relative positioning of the displays by visual object recognition and an optional manual calibration step.
Adapting Precomputed Radiance Transfer to Real-time Spectral Rendering
(The Eurographics Association, 2010) Schwenk, Karsten; Franke, Tobias; Drevensek, Timm; Kuijper, Arjan; Bockholt, Ulrich; Fellner, Dieter W.; H. P. A. Lensch and S. Seipel
Spectral rendering takes the full visible spectrum into account when calculating light-surface interaction and can overcome the well-known deficiencies of rendering with tristimulus color models. We present a variant of the precomputed radiance transfer algorithm that is tailored towards real-time spectral rendering on modern graphics hardware. Our method renders diffuse, self-shadowing objects with spatially varying spectral reflectance properties under distant, dynamic, full-spectral illumination. To achieve real-time frame rates and practical memory requirements we split the light transfer function into an achromatic part that varies per vertex and a wavelengthdependent part that represents a spectral albedo texture map. As an additional optimization, we project reflectance and illuminant spectra into an orthonormal basis. One area of application for our research is virtual design applications that require relighting objects with high color fidelity at interactive frame rates.Spectral rendering takes the full visible spectrum into account when calculating light-surface interaction and can overcome the well-known deficiencies of rendering with tristimulus color models. We present a variant of the precomputed radiance transfer algorithm that is tailored towards real-time spectral rendering on modern graphics hardware. Our method renders diffuse, self-shadowing objects with spatially varying spectral reflectance properties under distant, dynamic, full-spectral illumination. To achieve real-time frame rates and practical memory requirements we split the light transfer function into an achromatic part that varies per vertex and a wavelengthdependent part that represents a spectral albedo texture map. As an additional optimization, we project reflectance and illuminant spectra into an orthonormal basis. One area of application for our research is virtual design applications that require relighting objects with high color fidelity at interactive frame rates.
Adaptive Collapsing on Bounding Volume Hierarchies for Ray-Tracing
(The Eurographics Association, 2010) Pinto, André Susano; H. P. A. Lensch and S. Seipel
Ray tracing is a computationally intensive process, several tree data structures and heuristics have been developed to optimize it. This paper presents a new heuristic in the area, based on collapsing some nodes in order to achieve a smaller expected number of node-tests. Two ways of using this heuristic in Bounding Volume Hierarchies are presented as well as the cost-model used to drive the heuristic development and measure it s efficiency. Some procedures on integrating this heuristic with other optimizations are also discussedRay tracing is a computationally intensive process, several tree data structures and heuristics have been developed to optimize it. This paper presents a new heuristic in the area, based on collapsing some nodes in order to achieve a smaller expected number of node-tests. Two ways of using this heuristic in Bounding Volume Hierarchies are presented as well as the cost-model used to drive the heuristic development and measure it s efficiency. Some procedures on integrating this heuristic with other optimizations are also discussed
Adding Depth to Cartoons Using Sparse Depth (In)equalities
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Sykora, D.; Sedlacek, D.; Jinchao, S.; Dingliana, J.; Collins, S.
This paper presents a novel interactive approach for adding depth information into hand-drawn cartoon images and animations. In comparison to previous depth assignment techniques our solution requires minimal user effort and enables creation of consistent pop-ups in a matter of seconds. Inspired by perceptual studies we formulate a custom tailored optimization framework that tries to mimic the way that a human reconstructs depth information from a single image. Its key advantage is that it completely avoids inputs requiring knowledge of absolute depth and instead uses a set of sparse depth (in)equalities that are much easier to specify. Since these constraints lead to a solution based on quadratic programming that is time consuming to evaluate we propose a simple approximative algorithm yielding similar results with much lower computational overhead. We demonstrate its usefulness in the context of a cartoon animation production pipeline including applications such as enhancement, registration, composition, 3D modelling and stereoscopic display.
Advanced Material Appearance Models
(The Eurographics Association, 2010) Dorsey, Julie; Rushmeier, Holly; U. Assarsson and D. Weiskopf
This tutorial will cover the foundational elements of advanced material appearance models. For many years appearance models in computer graphics focused on general models for reflectance functions coupled with texture maps. However, even very common materials such as hair, skin, fabric, and rusting metal require more sophisticated models to appear realistic. In the tutorial we will begin by briefly reviewing basic reflectance models and the use of texture maps. We will then describe some common themes in advanced material models that include combining the effects of layers, groups of particles and or fibers. We will survey the detailed models necessary needed to model materials such as (but not limited to) skin (including pigmentation, pores, subsurface scattering), plants (including internal structure affecting scattering and characteristic shapes) and paints (including color flop and sparkle effects in automotive paints). In the next section of the tutorial we will treat the modeling of complex appearance due to aging and weathering processes. A general taxonomy of these effects will be presented, as well as methods to simulate and to capture these effects. The tutorial will close with a look at current trends in material modeling research. Important new trends include new interfaces for modeling materials, insights into material perception, and the availability of code and data for material models.
Animating Sand as a Surface Flow
(The Eurographics Association, 2010) Zhu, Bo; Yang, Xubo; H. P. A. Lensch and S. Seipel
This paper presents a new efficient method for animating sand and other granular materials in 3D scenes. Our method couples 2D and 3D simulation techniques in a physically based way. A surface flow model of granular material-the BCRE model-is used to separate sand piles into two layers: a surface flowing layer and a static layer. The surface layer is simulated using discrete element method (DEM) to capture the detailed flowing behavior, while the invisible and static layer is represented by a height field for efficiency. The matter transfer between the two layers is modeled based on the surface flow equations through a particle interface. We demonstrate that our method leads to significant improvements of computational efficiency compared to standard discrete element method, without sacrificing the rich 3D animation effects.
Articulated Billboards for Video-based Rendering
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Germann, Marcel; Hornung, Alexander; Keiser, Richard; Ziegler, Remo; Wuermlin, Stephan; Gross, Markus
We present a novel representation and rendering method for free-viewpoint video of human characters based on multiple input video streams. The basic idea is to approximate the articulated 3D shape of the human body using a subdivision into textured billboards along the skeleton structure. Billboards are clustered to fans such that each skeleton bone contains one billboard per source camera. We call this representation articulated billboards.In the paper we describe a semi-automatic, data-driven algorithm to construct and render this representation, which robustly handles even challenging acquisition scenarios characterized by sparse camera positioning, inaccurate camera calibration, low video resolution, or occlusions in the scene. First, for each input view, a 2D pose estimation based on image silhouettes, motion capture data, and temporal video coherence is used to create a segmentation mask for each body part. Then, from the 2D poses and the segmentation, the actual articulated billboard model is constructed by a 3D joint optimization and compensation for camera calibration errors. The rendering method includes a novel way of blending the textural contributions of each billboard and features an adaptive seam correction to eliminate visible discontinuities between adjacent billboards textures.Our articulated billboards do not only minimize ghosting artifacts known from conventional billboard rendering, but also alleviate restrictions to the setup and sensitivities to errors of more complex 3D representations and multiview reconstruction techniques. Our results demonstrate the flexibility and the robustness of our approach with high quality free-viewpoint video generated from broadcast footage of challenging, uncontrolled environments.
Automated Astrophysical Modeling with Shape
(The Eurographics Association, 2010) Wenger, S.; Steffen, W.; Koning, N.; Morisset, C.; Magnor, M.; Anders Hast and Ivan Viola
Three-dimensional models of complex astrophysical objects like galaxies or planetary nebulae have numerous applications in science, education and entertainment. The large distance of these objects, however, makes it difficult to obtain depth information, and conventional image-based 3D reconstruction algorithms and modeling tools are most often not able to faithfully reproduce their structure. Modeling is therefore typically performed manually by trained astronomers using specialized tools that incorporate additional information like spectral Doppler shift measurements into the modeling process. We present an extension to one such tool, Shape, that alleviates the most tedious part of the modeling process by automatically optimizing consistency of the models with observational data. Our contribution significantly reduces the necessary time for obtaining high-quality models and will be incorporated into future releases of Shape.
Automatic Composition of Motion Capture Animation for Music Synchronization
(The Eurographics Association, 2010) Xu, Jianfeng; Takagi, Koichi; Kawada, Ryoichi; H. P. A. Lensch and S. Seipel
To enrich the music experience, automatic generation of a CG music visualizer is attracting more and more attention, where 3D animation is composed to synchronize with the music using motion capture data. In this paper, we present a novel approach for the above purpose, where both beat and intensity are employed to synchronize the motion with the music.We extend the conventional unstructured motion graphs to structured motion graphs (called weighted motion graphs) using motion beat and intensity, where a best path is searched by dynamic programming to obtain beat-level synchronization. Our objective function is designed for the following three aspects: motion quality, cost from beat synchronization, and cost from intensity synchronization. Our experiments with a user study demonstrate that the proposed approach can effectively generate attractive animations for music synchronization with much less computational cost than the state-of-the-art alternative.
BetweenIT: An Interactive Tool for Tight Inbetweening
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Whited, Brian; Noris, Gioacchino; Simmons, Maryann; Sumner, Robert W.; Gross, Markus; Rossignac, Jarek
The generation of inbetween frames that interpolate a given set of key frames is a major component in the production of a 2D feature animation. Our objective is to considerably reduce the cost of the inbetweening phase by offering an intuitive and effective interactive environment that automates inbetweening when possible while allowing the artist to guide, complement, or override the results. Tight inbetweens, which interpolate similar key frames, are particularly time-consuming and tedious to draw. Therefore, we focus on automating these high-precision and expensive portions of the process. We have designed a set of user-guided semi-automatic techniques that fit well with current practice and minimize the number of required artist-gestures. We present a novel technique for stroke interpolation from only two keys which combines a stroke motion constructed from logarithmic spiral vertex trajectories with a stroke deformation based on curvature averaging and twisting warps. We discuss our system in the context of a feature animation production environment and evaluate our approach with real production data.
Bidirectional Search for Interactive Motion Synthesis
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lo, Wan-Yen; Zwicker, Matthias
We present an approach to improve the search efficiency for near-optimal motion synthesis using motion graphs. An optimal or near-optimal path through a motion graph often leads to the most intuitive result. However, finding such a path can be computationally expensive. Our main contribution is a bidirectional search algorithm. We dynamically divide the search space evenly and merge two search trees to obtain the final solution. This cuts the maximum search depth almost in half and leads to significant speedup. To illustrate the benefits of our approach, we present an interactive sketching interface that allows users to specify complex motions quickly and intuitively.
CAVER Viewer - the explorer of behaviour of tunnels in proteins
(The Eurographics Association, 2010) Kozlíková, Barbora; Sochor, Jirí; Anders Hast and Ivan Viola
Protein exploration in order to discover new medication has been the principal aim of biochemists. In combination with informatics the solution of this task can be faster, more accurate and also more intuitive and straightforward in comparison with traditional methods. Our CAVER Viewer application allows the exploration of protein structures and the visualization of results. It enables to find certain paths from the outer space around the molecule to the specific site inside the protein called the active site. The existence of these important paths (also called tunnels or channels) is crucial in the process of transferring some small molecule of substrate into this active site. Namely, the substrate enters the active site via these precomputed tunnels. There the chemical reaction between the substrate and protein can undergo. The product of this reaction can form the basis of a new medication. This poster describes the key aim of our research in the field of protein visualization, when we have to visualize the protein dynamics - movements of the molecule as well as the behaviour of its tunnels in time space.
A Computer Animation System for Creating Deaf-Accessible Math and Science Curriculum Materials
(The Eurographics Association, 2010) Hayward, Kyle; Adamo-Villani, Nicoletta; Lestina, Jason; L. Kjelldahl and G. Baronoski
In this paper we report the development and initial evaluation of the ASL system. The ASL system is an innovative software tool that allows educators of the Deaf to add sign language translation, in the form of 3D character animations, to digital learning content. Although this first iteration of the system is designed specifically to improve deaf students access to K-3 math educational materials, the system s open architecture allows supporting additional age groups and additional subjects. Results of an initial evaluation with educators of the Deaf and native ASL users show that the subjects were able to produce accurate and realistic animated ASL discourse using the system. However, the majority of the subjects found the system difficult to use; future work will focus on design and development of an intuitive, sketch-based user interface.
Computer Graphics for Information System Programmers
(The Eurographics Association, 2010) Linares-Pellicer, Jordi; Carrasquer-Moya, Empar; Esparza-Peidro, Javier; Micó-Tormos, Pau; L. Kjelldahl and G. Baronoski
An introductory computer graphics course is always a challenge. It is even more so if computer graphics is an additional component to a general computer science degree. In this instance, it is really important to discuss which computer graphics topics are relevant for tomorrow s programmers and engineers who are going to work mainly in Information Systems developments and data management software. The objective of this this paper is to consider what should be taught to future professionals who, not being directly involved in the development of specific computer graphics applications, will possibly need to use computer graphics in their developments. We will describe how this objective can be achieved by a carefully selected set of programming assignments.
Consensus Skeleton for Non-rigid Space-time Registration
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Zheng, Q.; Sharf, A.; Tagliasacchi, A.; Chen, B.; Zhang, H.; Sheffer, A.; Cohen-Or, D.
We introduce the notion of consensus skeletons for non-rigid space-time registration of a deforming shape. Instead of basing the registration on point features, which are local and sensitive to noise, we adopt the curve skeleton of the shape as a global and descriptive feature for the task. Our method uses no template and only assumes that the skeletal structure of the captured shape remains largely consistent over time. Such an assumption is generally weaker than those relying on large overlap of point features between successive frames, allowing for more sparse acquisition across time. Building our registration framework on top of the low-dimensional skeleton-time structure avoids heavy processing of dense point or volumetric data, while skeleton consensusization provides robust handling of incompatibilities between per-frame skeletons. To register point clouds from all frames, we deform them by their skeletons, mirroring the skeleton registration process, to jump-start a non-rigid ICP. We present results for non-rigid space-time registration under sparse and noisy spatio-temporal sampling, including cases where data was captured from only a single view.
Continuum Traffic Simulation
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Sewall, J.; Wilkie, D.; Merrell, P.; Lin, M. C.
We present a novel method for the synthesis and animation of realistic traffic flows on large-scale road networks. Our technique is based on a continuum model of traffic flow we extend to correctly handle lane changes and merges, as well as traffic behaviors due to changes in speed limit. We demonstrate how our method can be applied to the animation of many vehicles in a large-scale traffic network at interactive rates and show that our method can simulate believable traffic flows on publicly-available, real-world road data. We furthermore demonstrate the scalability of this technique on many-core systems.
Contrast-aware Halftoning
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Li, Hua; Mould, David
This paper proposes two variants of a simple but efficient algorithm for structure-preserving halftoning. Our algorithm extends Floyd-Steinberg error diffusion; the goal of our extension is not only to produce good tone similarity but also to preserve structure and especially contrast, motivated by our intuition that human perception is sensitive to contrast. By enhancing contrast we attempt to preserve and enhance structure also.Our basic algorithm employs an adaptive, contrast-aware mask. To enhance contrast, darker pixels should be more likely to be chosen as black pixels while lighter pixels should be more likely to be set as white. Therefore, when the positive error is diffused to nearby pixels in a mask, the dark pixels absorb less error and the light pixels absorb more. Conversely, negative error is distributed preferentially to dark pixels. We also propose using a mask with values that drop off steeply from the centre, intended to promote good spatial distribution. It is a very fast method whose speed mainly depends on the size of the mask. But this method suffers from distracting patterns.We then propose a variant on the basic idea which overcomes the first algorithm s shortcomings while maintaining its advantages through a priority-aware scheme. Rather than proceeding in random or raster order, we sort the image first; each pixel is assigned a priority based on its up-to-date distance to black or to white, and pixels with extreme intensities are processed earlier. Since we use the same mask strategy as before, we promote good spatial distribution and high contrast.We use tone similarity, structure similarity, and contrast similarity to validate our algorithm. Comparisons with recent structure-aware algorithms show that our method gives better results without sacrificing speed.
A curvature based lightning model for quasi-global diffuse illumination
(The Eurographics Association, 2010) Seipel, S.; Liu, F.; Ericsson, M.; Anders Hast and Ivan Viola
In this paper we present extensions to local illumination models that take into account light transport and shadowmasking effects in the neighborhood of the surface point under evaluation. Central to our approach is the idea that local curvature represents geometric features in the surrounding neighborhood of this point which have an attenuating or enhancing effect regarding the diffuse illumination of this point. We introduce a lighting model that controls the amount of locally scattered light from the neighborhood based on a local curvature metric. The properties we aim at modeling with this curvature-based illumination model can be found in highly diffuse reflecting materials such as for example snow.

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