EG2009

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https://diglib.eg.org/handle/10.2312/269

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Scalable real-time animation of rivers
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Yu, Qizhi; Neyret, Fabrice; Bruneton, Eric; Holzschuch, Nicolas
Many recent games and applications target the interactive exploration of realistic large scale worlds. These worlds consist mostly of static terrain models, as the simulation of animated fluids in these virtual worlds is computationally expensive. Adding flowing fluids, such as rivers, to these virtual worlds would greatly enhance their realism, but causes specific issues: as the user is usually observing the world at close range, small scale details such as waves and ripples are important. However, the large scale of the world makes classical methods impractical for simulating these effects. In this paper, we present an algorithm for the interactive simulation of realistic flowing fluids in large virtual worlds. Our method relies on two key contributions: the local computation of the velocity field of a steady flow given boundary conditions, and the advection of small scale details on a fluid, following the velocity field, and uniformly sampled in screen space.
Shadowing Dynamic Scenes with Arbitrary BRDFs
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Nowrouzezahrai, Derek; Kalogerakis, Evangelos; Fiume, Eugene
We present a real-time relighting and shadowing method for dynamic scenes with varying lighting, view and BRDFs. Our approach is based on a compact representation of reflectance data that allows for changing the BRDF at run-time and a data-driven method for accurately synthesizing self-shadows on articulated and deformable geometries. Unlike previous self-shadowing approaches, we do not rely on local blocking heuristics. We do not fit a model to the BRDF-weighted visibility, but rather only to the visibility that changes during animation. In this manner, our model is more compact than previous techniques and requires less computation both during fitting and at run-time. Our reflectance product operators can re-integrate arbitrary low-frequency view-dependent BRDF effects on-the-fly and are compatible with all previous dynamic visibility generation techniques as well as our own data-driven visibility model. We apply our reflectance product operators to three different visibility generation models, and our data-driven model can achieve framerates well over 300Hz.
An Analytical Solution to Single Scattering in Homogeneous Participating Media
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Pegoraro, Vincent; Parker, Steven G.
Despite their numerous applications, efficiently rendering participating media remains a challenging task due to the intricacy of the radiative transport equation. As they provide a generic means of solving a wide variety of problems, numerical methods are most often used to solve the air-light integral even under simplifying assumptions. In this paper, we present a novel analytical approach to single scattering from isotropic point light sources in homogeneous media. We derive the first closed-form solution to the air-light integral in isotropic media and extend this formulation to anisotropic phase functions. The technique relies neither on pre-computation nor on storage, and we provide a practical implementation allowing for an explicit control on the accuracy of the solutions. Finally, we demonstrate its quantitative and qualitative benefits over both previous numerical and analytical approaches.
Does Brief Exposure to a Self-avatar Effect Common Human Behaviors in Immersive Virtual Environments?
(The Eurographics Association, 2009) Streuber, Stephan; Rosa, Stephan de la; Trutoiu, Laura; Bülthoff, Heinrich H.; Mohler, Betty J.; P. Alliez and M. Magnor
A plausible assumption is that self-avatars increase the realism of immersive virtual environments (VEs), because self-avatars provide the user with a visual representation of his/her own body. Consequently having a self-avatar might lead to more realistic human behavior in VEs. To test this hypothesis we compared human behavior in VE with and without providing knowledge about a self-avatar with real human behavior in real-space. This comparison was made for three tasks: a locomotion task (moving through the content of the VE), an object interaction task (interacting with the content of the VE), and a social interaction task (interacting with other social entities within the VE). Surprisingly, we did not find effects of a self-avatar exposure on any of these tasks. However, participant s VE and real world behavior differed significantly. These results challenge the claim that knowledge about the self-avatar substantially influences natural human behavior in immersive VEs.
A Statistical Model of Human Pose and Body Shape
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Hasler, N.; Stoll, C.; Sunkel, M.; Rosenhahn, B.; Seidel, H.-P.
Generation and animation of realistic humans is an essential part of many projects in today s media industry. Especially, the games and special effects industry heavily depend on realistic human animation. In this work a unified model that describes both, human pose and body shape is introduced which allows us to accurately model muscle deformations not only as a function of pose but also dependent on the physique of the subject. Coupled with the model s ability to generate arbitrary human body shapes, it severely simplifies the generation of highly realistic character animations. A learning based approach is trained on approximately 550 full body 3D laser scans taken of 114 subjects. Scan registration is performed using a non-rigid deformation technique. Then, a rotation invariant encoding of the acquired exemplars permits the computation of a statistical model that simultaneously encodes pose and body shape. Finally, morphing or generating meshes according to several constraints simultaneously can be achieved by training semantically meaningful regressors.
TopoPlan: a topological path planner for real time human navigation under floor and ceiling constraints
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Lamarche, F.
In this article we present TopoPlan, a topological planner dedicated to real-time humanoid path-planning and motion adaptation to floor and ceiling constraints inside complex static environments. This planner analyzes unstructured 3D triangular meshes in order to automatically determine their topology. The analysis is based on a prismatic spatial subdivision which is analyzed, taking into account humanoid characteristics, in order to extract navigable surfaces and precisely identify environmental constraints such as floors, ceilings, walls, steps and bottlenecks. The technique also provides a lightweight roadmap computation covering all accessible free space. We demonstrate the properties of our topological planner within the context of two reactive motion control processes: an on-the-fly trajectory optimization and foot print generation process that correctly handles climbing of complex staircases, and a reactive ceiling adaptation process that handles beam avoidance and motion adaptation to irregular floors and ceilings. We further show that the computation cost of these processes is compatible with the real time animation of several dozens of virtual humans.
Computer Animation Curriculum: An Interdisciplinary Approach
(The Eurographics Association, 2009) Larboulette, Caroline; G. Domik and R. Scateni
This paper presents a Computer Animation curriculum worth 2.5 ECTS intended for graduate students enrolled in a Master s degree of Computer Graphics, Video Games and Virtual Reality. The content of the lecture fits the recommendations made for the topic of Animation I at the Computer Graphics Education Workshop [BCFH06] that was held in Vienna in 2006. The main novelty is, in addition to presenting a detailed curriculum, its interdis- ciplinary aspect. Indeed, while it is intended for a Computer Science degree, it also aims at teaching some artistic and software use aspects.
Interactive Geometric Simulation of 4D Cities
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Weber, Basil; Mueller, Pascal; Wonka, Peter; Gross, Markus
We present a simulation system that can simulate a three-dimensional urban model over time. The main novelty of our approach is that we do not rely on land-use simulation on a regular grid, but instead build a complete and inherently geometric simulation that includes exact parcel boundaries, streets of arbitrary orientation, street widths, 3D street geometry, building footprints, and 3D building envelopes. The second novelty is the fast simulation time and user interaction at interactive speed of about 1 second per time step.
A web-enabled Geovisual Analytics tool applied to OECD Regional Data
(The Eurographics Association, 2009) Jern, Mikael; Brezzi, Monica; Thygesen, Lars; D. Ebert and J. Krüger
Recent advances in web-enabled graphics technologies have the potential to make a dramatic impact on developing highly interactive Geovisual Analytics applications for the Internet. An emerging and challenging application domain is geovisualization of regional (sub-national) statistics. Higher integration driven by institutional processes and economic globalisation is eroding national borders and creating competition along regional lines in the world market. Sound information at sub-national level and benchmarking of regions across countries, therefore, has increased in importance in the policy agenda of many countries. In this paper, we introduce "OECD eXplorer" an interactive tool for analyzing and communicating gained insights and discoveries about spatial-temporal and multivariate OECD regional data. This database is a potential treasure chest for policy-makers, researchers and citizens to gain a better understanding of a region's structure and performance and to carry out analysis of territorial trends and disparities based on sound information comparable across countries. Many approaches and tools have been developed in spatial-related knowledge discovery but generally they do not scale well with dynamic visualization of larger spatial data on the Internet. In this context, we introduce a web-compliant Geovisual Analytics toolkit that supports a broad collection of functional components for analysis and validation, hypothesis generation, communicating and finally collaborating gained insights and knowledge based on a snapshot mechanism that captures, re-uses and shares task-related explorative events. An important ambition is to develop a generic highly interactive web "eXplorer" platform that can be the foundation for easy customization of similar dynamic web applications using different geographical boundaries and indicators and be publicly available. Given this global dimension, the dream of building a repository "statistical Wiki" of progress indicators, where experts and public users can use these generic tools to compare situations for two or more countries, regions or local communities, could be accomplished.
How to Write a Visualization Research Paper: The Art and Mechanics
(The Eurographics Association, 2009) Laramee, Robert S.; G. Domik and R. Scateni
This paper attempts to explain the mechanics of writing a research paper in visualization. This serves as a useful starting point for those who have never written a research paper before or have very little previous experience. Afterall, no one is born knowing how to write one. And yet, there are certain elements, a commonality, that should be found in virtually all good visualization research papers. We give our recommendations as to each section a good research paper consists of as well as what each section contains. This manuscript itself follows our recommended structure. We believe that paper writing should start with the abstract. The abstract can be approximately 6-12 sentences. It s a difficult starting point, but it forces the author to write down a concise description of what they re researching and what the benefits are. Chances are, if the author can t start out by writing an abstract, then it is not clear in the author s mind what the paper should be about. Of course the abstract will be refined and updated during the paper writing process. The abstract should concisely (1) identify the research topic, (2) describe the novelty of the presented work, and (3) identify the benefits and advantages that result.
On the Provision of a Comprehensive Computer Graphics Education in the Context of Computer Games: An Activity-Led Instruction Approach
(The Eurographics Association, 2009) Anderson, Eike Falk; Peters, Christopher E.; G. Domik and R. Scateni
Over the past decade the development of computer games which originated in academia with the creation of Spacewar at MIT in 1961 has evolved into an accepted academic discipline, closely related to the field of computer graphics. Games courses can be found embedded in traditional computer science degrees or as dedicated degree programmes for students aiming to work in the games industry. In this paper we present a studentcentred, activity-led approach to teaching computer graphics in the context of a computer games technology undergraduate degree. We describe our computer graphics related courses and demonstrate how they are formed by the activity-led teaching methodology.
A Hybrid GPU Rendering Pipeline for Alias-Free Hard Shadows
(The Eurographics Association, 2009) Hertel, Stefan; Hormann, Kai; Westermann, Rüdiger; D. Ebert and J. Krüger
We present a new GPU pipeline for rendering per-pixel exact shadows that are cast by point lights and parallel lights. Our approach is hybrid in that it uses kD-tree accelerated ray-tracing to determine shadow-ray intersections, and rasterization to effectively reduce both the number of shadow rays to be traversed and the number of sub-spaces to be considered along each of these rays. To achieve this we introduce conservative shadow maps, which store a conservative estimate of the first intersection with the scene for each possible shadow ray. A novel approach to build such a map is presented, which uses rasterization to compute for every shadow-map pixel the triangles intersecting this pixel. By exploiting the rasterization capacities of recent GPUs in combination with accurate ray-triangle intersection tests, we are able to efficiently compute alias-free shadows in high-resolution and spatially extended scenes where classical shadow mapping techniques have severe difficulties.
Implicit Contact Handling for Deformable Objects
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Otaduy, Miguel A.; Tamstorf, Rasmus; Steinemann, Denis; Gross, Markus
We present an algorithm for robust and efficient contact handling of deformable objects. By being aware of the internal dynamics of the colliding objects, our algorithm provides smooth rolling and sliding, stable stacking, robust impact handling, and seamless coupling of heterogeneous objects, all in a unified manner. We achieve dynamicsawareness through a constrained dynamics formulation with implicit complementarity constraints, and we present two major contributions that enable an efficient solution of the constrained dynamics problem: a time stepping algorithm that robustly ensures non-penetration and progressively refines the formulation of constrained dynamics, and a new solver for large mixed linear complementarity problems, based on iterative constraint anticipation. We show the application of our algorithm in challenging scenarios such as multi-layered cloth moving at high velocities, or colliding deformable solids simulated with large time steps.
A Cost Metric for Scene-Interior Ray Origins
(The Eurographics Association, 2009) Fabianowski, Bartosz; Fowler, Colin; Dingliana, John; P. Alliez and M. Magnor
Acceleration structures reducing the number of intersection tests are crucial for high ray tracing performance. The best acceleration structures are currently obtained using the surface area heuristic (SAH) which greedily optimizes a cost metric based on a series of heuristic assumptions about the rays. Noting that rays in many cases originate within the scene's bounding box, we assume a uniform distribution of their origins throughout the scene and derive alternative cost metrics. Our experimental results show that at a slight increase in acceleration structure build time, an improvement in ray tracing speed over the SAH is achieved for most scenes. A more accurate metric based on our assumptions yields even more reliable speed-ups at the cost of higher construction time. We conclude that making more realistic assumptions than the SAH is a promising route for better ray tracing acceleration.
Teaching Quaternions is not Complex
(The Eurographics Association, 2009) McDonald, John; G. Domik and R. Scateni
Quaternions are used in many fields of science and computing, but teaching them remains challenging. Students can have a great deal of trouble understanding essentially what quaternions are and how they can represent rotation matrices. In particular, the similarity transform qvq-1 which actually achieves rotation, can often be baffling even after they ve seen a full derivation. This paper outlines a constructive method for teaching quaternions, which allows students to build intuition about what quaternions are, and why simple multiplication is not adequate to represent a rotation. Through a set of examples, it demonstrates exactly how quaternions relate to rotation matrices, what goes wrong when qv is naively used to rotate vectors, and how the similarity transform fixes the problem.
Physically Guided Animation of Trees
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Habel, Ralf; Kusternig, Alexander; Wimmer, Michael
This paper presents a new method to animate the interaction of a tree with wind both realistically and in real time. The main idea is to combine statistical observations with physical properties in two major parts of tree animation. First, the interaction of a single branch with the forces applied to it is approximated by a novel efficient two step nonlinear deformation method, allowing arbitrary continuous deformations and circumventing the need to segment a branch to model its deformation behavior. Second, the interaction of wind with the dynamic system representing a tree is statistically modeled. By precomputing the response function of branches to turbulent wind in frequency space, the motion of a branch can be synthesized efficiently by sampling a 2D motion texture.Using a hierarchical form of vertex displacement, both methods can be combined in a single vertex shader, fully leveraging the power of modern GPUs to realistically animate thousands of branches and ten thousands of leaves at practically no cost.
EUROGRAPHICS Tutorial on Sketch Recognition
(The Eurographics Association, 2009) Hammond, T.; Paulson, B.; Eoff, B.; K. Museth and D. Weiskopf
Sketch recognition is the automated understanding of hand-drawn diagrams. Despite the prevalence of keyboards and mice, hand-drawings still pervade in education, design, and other diagrams. This full day tutorial explains why sketch recognition is important, the underlying algorithms, how sketch recognition can be used in traditional interfaces, and the field s experiences with sketch recognition used in different domains.
Time-of-Flight Sensors in Computer Graphics
(The Eurographics Association, 2009) Kolb, Andreas; Barth, Erhardt; Koch, Reinhard; Larsen, Rasmus; M. Pauly and G. Greiner
A growing number of applications depend on accurate and fast 3D scene analysis. Examples are model and lightfield acquisition, collision prevention, mixed reality, and gesture recognition. The estimation of a range map by image analysis or laser scan techniques is still a time-consuming and expensive part of such systems. A lower-priced, fast and robust alternative for distance measurements are Time-of-Flight (ToF) cameras. Recently, significant improvements have been made in order to achieve low-cost and compact ToF-devices, that have the potential to revolutionize many fields of research, including Computer Graphics, Computer Vision and Man Machine Interaction (MMI). These technologies are starting to have an impact on research and commercial applications. The upcoming generation of ToF sensors, however, will be even more powerful and will have the potential to become "ubiquitous real-time geometry devices" for gaming, web-conferencing, and numerous other applications. This STAR gives an account of recent developments in ToF-technology and discusses the current state of the integration of this technology into various graphics-related applications.
Arches: a Framework for Modeling Complex Terrains
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Peytavie, A.; Galin, E.; Grosjean, J.; Merillou, S.
In this paper, we present a framework for representing complex terrains with such features as overhangs, arches and caves and including different materials such as sand and rocks. Our hybrid model combines a volumetric discrete data structure that stores the different materials and an implicit representation for sculpting and reconstructing the surface of the terrain. Complex scenes can be edited and sculpted interactively with high level tools. We also propose an original rock generation technique that enables us to automatically generate complex rocky sceneries with piles of rocks without any computationally demanding physically-based simulation.
Deblurring by Matching
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Ancuti, Cosmin; Ancuti, Codruta Orniana; Bekaert, Philippe
Restoration of the photographs damaged by the camera shake is a challenging task that manifested increasing attention in the recent period. Despite of the important progress of the blind deconvolution techniques, due to the ill-posed nature of the problem, the finest details of the kernel blur cannot be recovered entirely. Moreover, the additional constraints and prior assumptions make these approaches to be relative limited.In this paper we introduce a novel technique that removes the undesired blur artifacts from photographs taken by hand-held digital cameras. Our approach is based on the observation that in general several consecutive photographs taken by the users share image regions that project the same scene content. Therefore, we took advantage of additional sharp photographs of the same scene. Based on several invariant local feature points, filtered from the given blurred/non-blurred images, our approach matches the keypoints and estimates the blur kernel using additional statistical constraints.We also present a simple deconvolution technique that preserves edges while minimizing the ringing artifacts in the restored latent image. The experimental results prove that our technique is able to infer accurately the blur kernel while reducing significantly the artifacts of the spoilt images.

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