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Item RTSG: Ray Tracing for X3D via a Flexible Rendering Framework(The Eurographics Association, 2009) Rubinstein, Dmitri; Georgiev, Iliyan; Schug, Benjamin; Slusallek, Philipp; Dieter W. Fellner and Alexei Sourin and Johannes Behr and Krzysztof WalczakVRML and X3D are the most widely adopted standards for interactive 3D content interchange. However, they are both designed around the common restricted functionality available in hardware graphics processors. Thus, most existing scene graph implementations are tightly integrated with rasterization APIs, which have difficulties simulating advanced global lighting effects. Conversely, complex photo-realistic effects are naturally supported by ray tracing based rendering algorithms [Glassner 1989]. Due to recent research advances and the constantly increasing computing power of commodity PCs, ray tracing is emerging as an interesting alternative for interactive applications. In this paper we present RTSG (Real-Time Scene Graph), a flexible scene management and rendering system. RTSG is X3D-compliant and has been designed to efficiently support both ray tracing and rasterization using a backend-independent rendering infrastructure. We describe two ray tracing and one rasterization backends and demonstrate that they achieve real-time rendering performance.Item Experiment-based Modeling, Simulation and Validation of Interactions between VirtualWalkers(ACM SIGGRAPH / Eurographics Association, 2009) Pettré, Julien; Ondrej, Jan; Olivier, Anne-Hélène; Cretual, Armel; Donikian, Stéphane; Eitan Grinspun and Jessica HodginsAn interaction occurs between two humans when they walk with converging trajectories. They need to adapt their motion in order to avoid and cross one another at respectful distance. This paper presents a model for solving interactions between virtual humans. The proposed model is elaborated from experimental interactions data. We first focus our study on the pair-interaction case. In a second stage, we extend our approach to the multiple interactions case. Our experimental data allow us to state the conditions for interactions to occur between walkers, as well as each one's role during interaction and the strategies walkers set to adapt their motion. The low number of parameters of the proposed model enables its automatic calibration from available experimental data. We validate our approach by comparing simulated trajectories with real ones. We also provide comparison with previous solutions. We finally discuss the ability of our model to be extended to complex situations.Item Extending X3D for Distributed Multimedia Processing and Control(The Eurographics Association, 2009) Repplinger, Michael; Löffler, Alexander; Schug, Benjamin; Slusallek, Philipp; Dieter W. Fellner and Alexei Sourin and Johannes Behr and Krzysztof WalczakWeb-based applications of interactive 3D computer graphics are showing a tendency to get more interconnected and visually complex. Virtual communities like Second Life demand realism not only in terms of realistic rendering, but also in terms of integrated multimedia content. For these Web-based applications, X3D is the ISO-standard way to specify and manipulate scene descriptions. In terms of multimedia integration, however, X3D offers to specify content only in the form of URLs pointing to files. Modern middleware for distributed multimedia, on the other hand, allows applications to harness the full range of multimedia processing as well as transparent use and full control of both local and remote components. Integrating a full multimedia processing pipeline into X3D would enable Web authors to use, for example, streaming media, post-processing on media streams, or routing between scene elements (e.g., sensors) and elements of multimedia processing (e.g., TV cards). A full integration of multimedia in X3D is yet missing. In this paper, we propose X3D extensions for a seamless mapping of a distributed multimedia flow graph onto an X3D scene graph, making all the features of a distributed multimedia middleware accessible and usable within an X3D scene. We present our proposed specification and implementation of multimedia nodes for X3D. Using examples and implemented X3D application scenarios, we show the simplicity and feasibility of our approach.Item A Point-based Method for Animating Incompressible Flow(ACM SIGGRAPH / Eurographics Association, 2009) Sin, Funshing; Bargteil, Adam W.; Hodgins, Jessica K.; Eitan Grinspun and Jessica HodginsIn this paper, we present a point-based method for animating incompressible flow. The advection term is handled by moving the sample points through the flow in a Lagrangian fashion. However, unlike most previous approaches, the pressure term is handled by performing a projection onto a divergence-free field. To perform the pressure projection, we compute a Voronoi diagram with the sample points as input. Borrowing from Finite Volume Methods, we then invoke the divergence theorem and ensure that each Voronoi cell is divergence free. To handle complex boundary conditions, Voronoi cells are clipped against obstacle boundaries and free surfaces. The method is stable, flexible and combines many of the desirable features of point-based and grid-based methods. We demonstrate our approach on several examples of splashing and streaming liquid and swirling smoke.Item Spatial Deformation Transfer(ACM SIGGRAPH / Eurographics Association, 2009) Ben-Chen, Mirela; Weber, Ofir; Gotsman, Craig; Eitan Grinspun and Jessica HodginsMuch effort is invested in generating natural deformations of three-dimensional shapes. Deformation transfer simplifies this process by allowing to infer deformations of a new shape from existing deformations of a similar shape. Current deformation transfer methods can be applied only to shapes which are represented as a single component manifold mesh, hence their applicability to real-life 3D models is somewhat limited. We propose a novel deformation transfer method, which can be applied to a variety of shape representations tet-meshes, polygon soups and multiple-component meshes. Our key technique is deformation of the space in which the shape is embedded. We approximate the given source deformation by a harmonic map using a set of harmonic basis functions. Then, given a sparse set of user-selected correspondence points between the source and target shapes, we generate a deformation of the target shape which has differential properties similar to those of the source deformation. Our method requires only the solution of linear systems of equations, and hence is very robust and efficient. We demonstrate its applicability on a wide range of deformations, for different shape representations.Item ADML: A framework for representing inhabitants in 3D Virtual Worlds(The Eurographics Association, 2009) Oyarzun, David; Ortiz, Amalia; Carretero, Maria del Puy; Gelissen, Jean; Garcia-Alonso, Alex; Sivan, Yesha; Dieter W. Fellner and Alexei Sourin and Johannes Behr and Krzysztof WalczakLast years, a new fashion over Internet and computer networks has been established: the 3D virtual worlds. Reports about Future Internet predict virtual worlds will play a major role in the configuration of the future network. They bet on those virtual environments will encompass the ability to become highly adaptive to user preferences (having into account eInclusion aspects), and they will provide a high level of interoperability. However, current 3D virtual worlds are far from cover these issues. This work is focused in providing a preliminary solution about customization and interoperability in the field of avatars representation. They are a key element in the 3D virtual worlds because using 3D avatars is a common way for representing virtual world inhabitants. First of all, nowadays there is not a way for defining all the avatar features that are important for simulating a real person, and for defining their identity. Besides, features that can be specified are usually defined in a closed and proprietary format that does not allow migration among virtual worlds. Thirdly, eInclusion aspects are not taken into account. This work proposes a preliminary framework for specifying a complete avatar identity by means of features that are not dependent on the virtual world context or interaction events. Those are appearance, personality and communication skills. Moreover, for providing a tool that describes the framework, the base for a new XML-based language -ADML- has been created. The language will allow specify avatar identity features taking into account eInclusion aspects and it will allow migration among worlds. Part of this language has been accepted into the new MPEG-V standard proposal.Item A Point-Based Method for Animating Elastoplastic Solids(ACM SIGGRAPH / Eurographics Association, 2009) Gerszewski, Dan; Bhattacharya, Haimasree; Bargteil, Adam W.; Eitan Grinspun and Jessica HodginsIn this paper we describe a point-based approach for animating elastoplastic materials. Our primary contribution is a simple method for computing the deformation gradient for each particle in the simulation. The deformation gradient is computed for each particle by finding the affine transformation that best approximates the motion of neighboring particles over a single timestep. These transformations are then composed to compute the total deformation gradient that describes the deformation around a particle over the course of the simulation. Given the deformation gradient we can apply arbitrary constitutive models and compute the resulting elastic forces. Our method has two primary advantages: we do not store or compare to an initial rest configuration and we work directly with the deformation gradient. The first advantage avoids poor numerical conditioning and the second naturally leads to a multiplicative model of deformation appropriate for finite deformations. We demonstrate our approach on a number of examples that exhibit a wide range of material behaviors.Item X3DOM - A DOM-based HTML5/ X3D Integration Model(The Eurographics Association, 2009) Behr, Johannes; Eschler, Peter; Jung, Yvonne; Zöllner, Michael; Dieter W. Fellner and Alexei Sourin and Johannes Behr and Krzysztof WalczakWe present a model that allows to directly integrate X3D nodes into HTML5 DOM content. This model tries to fulfill the promise of the HTML5 specification, which references X3D for declarative 3D scenes but does not define a specific integration mode. The goal of this model is to ease the integration of X3D in modern web applications by directly mapping and synchronizing live DOM elements to a X3D scene model. This is a very similar approach to the current SVG integration model for 2D graphics. Furthermore, we propose a framework that includes a new X3D Profile for the DOM integration. This profile should make implementation simple, but in addition we show that the current X3D runtime model still scales well. A detailed discussion includes DOM integration issues like events, namespaces and scripting. We finally propose an implementation framework that should work with multiple browser frontends (e.g. Firefox andWebKit) and different X3D runtime backends. We hope to connect the technologies and the X3D/ W3C communities with this proposal and outline a model, how an integration without plugins could work. Moreover, we hope to inspire further work, which could lead to a native X3D implementation in browsers similar to the SVG implementations today.Item Exact volume preserving skinning with shape control(ACM SIGGRAPH / Eurographics Association, 2009) Rohmer, Damien; Hahmann, Stefanie; Cani, Marie-Paule; Eitan Grinspun and Jessica HodginsIn the real world, most objects do not loose volume when they deform: they may for instance compensate a local compression by inflating in the orthogonal direction, or, in the case of a character, preserve volume through specific bulges and folds. This paper presents a novel extension to smooth skinning, which not only offers an exact control of the object volume, but also enables the user to specify the shape of volume-preserving deformations through intuitive 1D profile curves. The method, a geometric post-processing to standard smooth skinning, perfectly fits into the usual production pipeline. It can be used whatever the desired locality of volume correction and does not bring any constraint on the original mesh. Several behaviors mimicking the way rubber-like materials and organic shapes respectively deform can be modeled. An improved algorithm for robustly computing skinning weights is also provided, making the method directly usable on complex characters, even for non-experts.Item An Incremental SMLAOI Algorithm for Progressive Downloading Large Scale WebVR Scenes(The Eurographics Association, 2009) Wang, Wei; Jia, Jinyuan; Dieter W. Fellner and Alexei Sourin and Johannes Behr and Krzysztof WalczakInteractive downloading huge virtual scenes on Internet is always a challenging task of large scale DVE(Distributed Virtual Environment) systems. Along classical progressive transmission mechanism based on AOI (Area of Interest), this paper proposes a new concept SMLAOI (Scalable Multi-Layer AOI). Then,presents an integer incremental SMLAOI culling algorithm without multiplication, divisions and floating calculations, which allows the WebVR regions nearer to current viewpoint to download with higher delivery priority, and reduces time that a user need to wait for initial scenes. Finally a framework of progressive downloading large scale WebVR scenes based C/S is designed.