EG2010

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

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Seamless Montage for Texturing Models
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Gal, Ran; Wexler, Yonatan; Ofek, Eyal; Hoppe, Hugues; Cohen-Or, Daniel
We present an automatic method to recover high-resolution texture over an object by mapping detailed photographs onto its surface. Such high-resolution detail often reveals inaccuracies in geometry and registration, as well as lighting variations and surface reflections. Simple image projection results in visible seams on the surface. We minimize such seams using a global optimization that assigns compatible texture to adjacent triangles. The key idea is to search not only combinatorially over the source images, but also over a set of local image transformations that compensate for geometric misalignment. This broad search space is traversed using a discrete labeling algorithm, aided by a coarse-to-fine strategy. Our approach significantly improves resilience to acquisition errors, thereby allowing simple and easy creation of textured models for use in computer graphics.
A Data-driven Segmentation for the Shoulder Complex
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Hong, Q Youn; Park, Sang Il; Hodgins, Jessica K.
The human shoulder complex is perhaps the most complicated joint in the human body being comprised of a set of three bones, muscles, tendons, and ligaments. Despite this anatomical complexity, computer graphics models for motion capture most often represent this joint as a simple ball and socket. In this paper, we present a method to determine a shoulder skeletal model that, when combined with standard skinning algorithms, generates a more visually pleasing animation that is a closer approximation to the actual skin deformations of the human body. We use a data-driven approach and collect ground truth skin deformation data with an optical motion capture system with a large number of markers (200 markers on the shoulder complex alone). We cluster these markers during movement sequences and discover that adding one extra joint around the shoulder improves the resulting animation qualitatively and quantitatively yielding a marker set of approximately 70 markers for the complete skeleton. We demonstrate the effectiveness of our skeletal model by comparing it with ground truth data as well as with recorded video. We show its practicality by integrating it with the conventional rendering/animation pipeline.
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.
Simple and Robust Iterative Importance Sampling of Virtual Point Lights
(The Eurographics Association, 2010) Georgiev, Iliyan; Slusallek, Philipp; H. P. A. Lensch and S. Seipel
We present a simple and practical algorithm for importance sampling virtual point lights (VPLs) [Kel97], suitable for multi-pass rendering. During VPL distribution, a Russian roulette decision accepts each VPL proportionally to its estimated contribution to the final image. As a result, more VPLs are concentrated in areas that illuminate the visible parts of the scene, at the cost of a negligible performance overhead in the preprocessing phase. As VPLs are sampled independently and proportionally to their camera importance, the algorithm is trivial to parallelize and remains efficient for low sampling rates. We show that this sampling scheme is well suited to both well illuminated scenes as well as for difficult visibility conditions. Moreover, in contrast to bidirectional and Metropolis VPL sampling [SIMP06, SIP07], the algorithm is fast and very simple to implement, and uses a single Monte Carlo sampler, making it easier to maintain good stratification.We present a simple and practical algorithm for importance sampling virtual point lights (VPLs) [Kel97], suitable for multi-pass rendering. During VPL distribution, a Russian roulette decision accepts each VPL proportionally to its estimated contribution to the final image. As a result, more VPLs are concentrated in areas that illuminate the visible parts of the scene, at the cost of a negligible performance overhead in the preprocessing phase. As VPLs are sampled independently and proportionally to their camera importance, the algorithm is trivial to parallelize and remains efficient for low sampling rates. We show that this sampling scheme is well suited to both well illuminated scenes as well as for difficult visibility conditions. Moreover, in contrast to bidirectional and Metropolis VPL sampling [SIMP06, SIP07], the algorithm is fast and very simple to implement, and uses a single Monte Carlo sampler, making it easier to maintain good stratification.
Global Illumination Compensation for Spatially Augmented Reality
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Sheng, Yu; Yapo, Theodore C.; Cutler, Barbara
When projectors are used to display images on complex, non-planar surface geometry, indirect illumination between the surfaces will disrupt the final appearance of this imagery, generally increasing brightness, decreasing contrast, and washing out colors. In this paper we predict through global illumination simulation this unintentional indirect component and solve for the optimal compensated projection imagery that will minimize the difference between the desired imagery and the actual total illumination in the resulting physical scene. Our method makes use of quadratic programming to minimize this error within the constraints of the physical system, namely, that negative light is physically impossible. We demonstrate our compensation optimization in both computer simulation and physical validation within a table-top spatially augmented reality system. We present an application of these results for visualization of interior architectural illumination. To facilitate interactive modifications to the scene geometry and desired appearance, our system is accelerated with a CUDA implementation of the QP optimization method.
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.
Theory and Methods of Lightfield Photography
(The Eurographics Association, 2010) Georgiev, Todor; Lumsdaine, Andrew; U. Assarsson and D. Weiskopf
Computational photography is based on capturing and processing discrete representations of all the light rays in the 3D space of a scene. Compared to conventional photography, which captures 2D images, computational photography captures the entire 4D 'lightfield' - the full 4D radiance. To multiplex the 4D radiance onto conventional 2D sensors, light-field photography demands sophisticated optics and imaging technology. At the same time, 2D image creation is based on creating 2D projections of the 4D radiance. <br>This course presents light-field analysis in a rigorous, yet accessible, mathematical way, which often leads to surprisingly direct solutions. The mathematical foundations will be used to develop computational methods for lightfield processing and image rendering, including digital refocusing and perspective viewing. While emphasizing theoretical understanding, we also explain approaches and engineering solutions to practical problems in computational photography. <br>As part of the course, we will demonstrate a number of working light-field cameras that implement different methods for radiance capture, including the microlens approach of Lippmann and the plenoptic camera; the focused plenoptic camera, the Adobe lens-prism camera; and a new camera using a mosquito net mask. Various computational techniques for processing captured light-fields will also be demonstrated, including the focused plenoptic camera and real-time radiance rendering.
A Framework for Simulation-Event Triggered Animations
(The Eurographics Association, 2010) Hauck, R.; Künzler, U.; Anders Hast and Ivan Viola
We present a generic framework which uses a CAVE virtual environment for the optimization of surgical workflows and operation room medical equipment arrangements. The framework combines an event-driven simulation with 3D character animations and focuses on the separation of the workflow logic from the geometrical representation of the 3D objects.
Simplex and Diamond Hierarchies: Models and Applications
(The Eurographics Association, 2010) Weiss, K.; Floriani, L. De; Helwig Hauser and Erik Reinhard
Hierarchical spatial decompositions are a basic modeling tool in a variety of application domains. Several papers on this subject deal with hierarchical simplicial decompositions generated through simplex bisection. Such decompositions, originally developed for finite elements, are extensively used as the basis for multiresolution models of scalar fields, such as terrains, and static or time-varying volume data. They have also been used as an alternative to quadtrees and octrees as spatial access structures and in other applications. In this state of the art report, we distinguish between approaches that focus on a specific dimension and those that apply to all dimensions. The primary distinction among all such approaches is whether they treat the simplex or clusters of simplexes, called diamonds, as the modeling primitive. This leads to two classes of data structures and to different query approaches. We present the hierarchical models in a dimension independent manner, and organize the description of the various applications, primarily interactive terrain rendering and isosurface extraction, according to the dimension of the domain.
Undoing Subpixel Rendering for Better Screenshots
(The Eurographics Association, 2010) Loviscach, J.; Anders Hast and Ivan Viola
Subpixel rendering employs the spatial layout of the red, green, and blue slices of a single square pixel on a screen to enhance the horizontal resolution. This method has become the de-facto standard for displaying text. Printed screenshots and screen magnifier software, however, reveal color seams. This is particularly vexing when screenshots are to be printed in color at a larger-than-normal scale, for instance in a tutorial article in a computing magazine. Hence, this work introduces a method for automatic correction.
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.
Progress in Rendering and Modeling for Digital Planetariums
(The Eurographics Association, 2010) Magnor, Marcus; Sen, Pradeep; Kniss, Joe; Angel, Edward; Wenger, Stephan; Matthew Cooper and Kari Pulli
Contemporary challenges in the production of digital planetarium shows include real-time rendering realism as well as the creation of authentic content. While interactive, live performance is a standard feature of professional digital-dome planetarium software today, support for physically correct rendering of astrophysical phenomena is still often limited. Similarly, the tools currently available for planetarium show production do not offer much assistance towards creating scientifically accurate models of astronomical objects. Our paper presents recent results from computer graphics research, offering solutions to contemporary challenges in digital planetarium rendering and modeling. Incorporating these algorithms into the next generation of dome display software and production tools will help advance digital planetariums toward make full use of their potential.
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.
Human Motion Synthesis with Optimization-based Graphs
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Ren, Cheng; Zhao, Liming; Safonova, Alla
Continuous constrained optimization is a powerful tool for synthesizing novel human motion segments that are short. Graph-based motion synthesis methods such as motion graphs and move trees are popular ways to synthesize long motions by playing back a sequence of existing motion segments. However, motion graphs only support transitions between similar frames, and move trees only support transitions between the end of one motion segment and the start of another. In this paper, we introduce an optimization-based graph that combines continuous constrained optimization with graph-based motion synthesis. The constrained optimization is used to create a vast number of complex realistic-looking transitions in the graph. The graph can then be used to synthesize long motions with non-trivial transitions that for example allow the character to switch its behavior abruptly while retaining motion naturalness. We also propose to build this graph semi-autonomously by requiring a user to classify generated transitions as acceptable or not and explicitly minimizing the amount of required classifications. This process guarantees the quality consistency of the optimization-based graph at the cost of limited user involvement.
Printed Patterns for Enhanced Shape Perception of Papercraft Models
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Xue, Su; Chen, Xuejin; Dorsey, Julie; Rushmeier, Holly
Papercraft models can serve as inexpensive prototypes in shape design applications. However, in making the models some geometric detail is necessarily lost, and artificial creases may be visible, thereby limiting the utility of these models. To compensate for these practical limitations, we introduce the use of printed patterns on papercraft models to enhance the perception of the shape they are intended to represent. We propose pattern generation schemes that modulate the sizes, directions, and densities of glyphs of patterns based on geometric attributes. We present a psychophysical experiment designed to explore the effect that printed patterns have on the perception of the papercraft model shapes. We find that models with printed patterns are perceived to represent the intended shape more accurately, and, further, that the type of printed pattern has an impact on the perceived shape.
Real-time Realistic Ocean Lighting using Seamless Transitions from Geometry to BRDF
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Bruneton, Eric; Neyret, Fabrice; Holzschuch, Nicolas
Realistic animation and rendering of the ocean is an important aspect for simulators, movies and video games. By nature, the ocean is a difficult problem for Computer Graphics: it is a dynamic system, it combines wave trains at all scales, ranging from kilometric to millimetric. Worse, the ocean is usually viewed at several distances, from very close to the viewpoint to the horizon, increasing the multi-scale issue, and resulting in aliasing problems. The illumination comes from natural light sources (the Sun and the sky dome), is also dynamic, and often underlines the aliasing issues. In this paper, we present a new algorithm for modelling, animation, illumination and rendering of the ocean, in real-time, at all scales and for all viewing distances. Our algorithm is based on a hierarchical representation, combining geometry, normals and BRDF. For each viewing distance, we compute a simplified version of the geometry, and encode the missing details into the normal and the BRDF, depending on the level of detail required. We then use this hierarchical representation for illumination and rendering. Our algorithm runs in real-time, and produces highly realistic pictures and animations.
Efficient Free Path Sampling in Inhomogeneous Media
(The Eurographics Association, 2010) Szirmay-Kalos, László; Tóth, Balázs; Magdics, Milán; Csébfalvi, Balázs; Anders Hast and Ivan Viola
This paper presents an efficient algorithm to sample free path in inhomogeneous participating media. The method is based on the concept of mixing virtual particles to the medium, that complete the extinction coefficient to a piece-wise constant function. We use the sampling formulae developed for piece-wise homogeneous medium, but decide randomly whether a real or a virtual particle is hit.
Real-time Rendering of Heterogeneous Translucent Objects with Arbitrary Shapes
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Wang, Yajun; Wang, Jiaping; Holzschuch, Nicolas; Subr, Kartic; Yong, Jun-Hai; Guo, Baining
We present a real-time algorithm for rendering translucent objects of arbitrary shapes. We approximate the scattering of light inside the objects using the diffusion equation, which we solve on-the-fly using the GPU. Our algorithm is general enough to handle arbitrary geometry, heterogeneous materials, deformable objects and modifications of lighting, all in real-time. In a pre-processing step, we discretize the object into a regular 4-connected structure (QuadGraph). Due to its regular connectivity, this structure is easily packed into a texture and stored on the GPU. At runtime, we use the QuadGraph stored on the GPU to solve the diffusion equation, in real-time, taking into account the varying input conditions: Incoming light, object material and geometry. We handle deformable objects, provided the deformation does not change the topological structure of the objects.
Fitted BVH for Fast Raytracing of Metaballs
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Gourmel, Olivier; Pajot, Anthony; Paulin, Mathias; Barthe, Loic; Poulin, Pierre
Raytracing metaballs is a problem that has numerous applications in the rendering of dynamic soft objects such as fluids. However, current techniques are either limited in the visual effects that they can render or their performance drops as the number of metaballs and their density increase. We present a new acceleration structure based on BVH and kd-tree for efficient raytracing of a large number of metaballs. This structure is built from an adapted SAH using a fast greedy algorithm and allows the visualization of several hundreds of thousands metaballs at interactive-to-real-time framerates. Our method can handle arbitrary rays to simulate any complex secondary effects such as reflections or soft shadows, and is robust with respect to the density of metaballs. We achieve this performance thanks to a balanced CPU-GPU (using CUDA) implementation of the animation, structure creation, and rendering.
GPU Destruction: Real-Time Procedural Demolition of Virtual Environments
(The Eurographics Association, 2010) Morris, Derek John; Anderson, Eike Falk; Anders Hast and Ivan Viola
We introduce a method for the real-time simulation of destructible materials for use within videogame environ- ments. Our system combines a number of existing techniques in a Graphics Processing Unit (GPU) based imple- mentation that employs procedural geometry generation to reduce content creation times while retaining artist control

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