EG2003
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Item Open Issues in Photo-realistic Rendering(Eurographics Association, 2003) Purgathofer, WernerFor more than two decades Computer graphics researchers have tried to achieve photo-realism in their images as reliable as possible, mainly by simulating the physical laws of light and adding one effect after the other. The recent years have brought a change of efforts towards real-time methods, easy-to-use systems, integration with vision, modelling tools and the like. The quality of images is mostly accepted as sufficient for real world applications, but where are we really? There are still numerous problems to be solved, and there is notable progress in these areas. No question, the plug-in philosophy of some commercial products has enabled several of these new techniques to be distributed quite fast. But unfortunately, many other of these developments happen in isolated systems for the pure purpose of publication, and never make it into commercial software. This presentation wants to make people more aware of such activities, and evaluate the steps we still have to go towards perfect photo-realism. The talk will start with an attempt to give a brief overview of the rendering history, highlighting the main research directions at different times. It will explain the driving forces of the developments, which are complexity, speed, and accuracy, and maybe also expression in recent years. Solved and unsolved areas are examined, and compared to practically solved but theoretically incomplete topics such as translucency, tone mapping, light source and BTF descriptions, and error metrics for image quality evaluation. The difference lies mainly in the difference between believable, correct, and predictive images. Also, for really realistic images modelling complexity is still an issue. Finally, some recent work on polarization and fluorescence is presented.Item Automatic High Level Avatar Guidance Based on Affordance of Movement(Eurographics Association, 2003) Michael, Despina; Chrysanthou, YiorgosAs virtual cities become ever more common and more extensive, the need to populate them with virtual pedestrians grows. One of the problems to be resolved for the virtual population is the behaviour simulation. Currently specifying the behaviour requires a lot of laborious work. In this paper we propose a method for automatically deriving the high level behaviour of the avatars. We introduce to the Graphics community a new method adapted from ideas recently presented in the Architecture literature. In this method, the general avatar movements are derived from an analysis of the structure of the architectural model. The analysis tries to encode Gibsons 7 principle of affordance, interpreted here as: pedestrians are more attracted towards directions with greater available walkable surface. We have implemented and tested the idea in a 2x2 km2 model of the city of Nicosia. Initial results indicate that the method, although simple, can automatically and efficiently populate the model with realistic results.Item On the characterization of avatars in Distributed Virtual Worlds(Eurographics Association, 2003) Morillo, Pedro; Fernandez, Marcos; Orduna, Juan ManuelCurrent Distributed Virtual Environment (DVE) systems run simulations based on a server-network architecture, where the population of avatars should be properly assigned to the servers in the DVE. This goal, called partitioning problem, is a hot research problem in the field of networked 3D real time graphics. Some approaches have been proposed for resolving this problem, all of them based on a very basic model which describes the behaviour of an avatar in a virtual world. This model estimates the workload that a given avatar adds to its server as an independent and static value. In order to design scalable and accurate partitioning schemes we propose a new characterization of the workload generated by the avatars in the system. In this model, the workload is computed as a function of two factors: avatar movement rate and factor of presence. Evaluation results show that this proposed model correlates with real systems properly, providing an accurate abstraction of avatars for load balancing purposes.Item Research Problems for Creating Digital Actors(Eurographics Association, 2003) Ko, Hyeong-Seok; Choi, Kwang-Jin; Choi, Min Gyu; Tak, Seyoon; Choe, Byoungwon; Song, Oh-YoungAn interesting challenge for the computer graphics community is to use computer graphics technology to simulate digital actors that seem so real that people cannot tell whether they are animated or real. Our group is engaged in an ongoing project to develop and integrate the techniques required for creating digital actors. In particular, our research has been focused on components such as facial animation, hair animation, clothing animation, and body animation, which are crucial to the successful realization of digital actors. This article summarizes the results of our research on those topics, reviews other approaches that have been taken in digital actor research, and outlines the challenges that must be overcome in this area.Item Persepolis: Recovering history with a handheld camera(Eurographics Association, 2003) Sainz, M.; Susin, A.; Cervantes, A.; Bagherzadeh, N.In this paper we present new improvements to our novel pipeline for image based modeling of objects using a camcorder. Our system takes an uncalibrated sequence of images recorded around a scene, it automatically recovers the underlying 3D structure and camera path and then a volumetric scene reconstruction is performed using a hardware accelerated voxel carving approach. Finally a triangular mesh is obtained and the available information from the images is combined to generate a full 3D photo-realistic reconstruction. As an application, we use this system to reconstruct parts of the archeological site of Persepolis (Iran).Item Combining 3D Scans and Motion Capture for Realistic Facial Animation(Eurographics Association, 2003) Breidt, Martin; Wallraven, Christian; Cunningham, Douglas W.; Buelthoff, Heinrich H.We present ongoing work on the development of new methods for highly realistic facial animation. One of the main contributions is the use of real-world, high-precision data for both the timing of the animation and the deformation of the face geometry. For animation, a set of morph shapes acquired through a 3D scanner is linearly morphed according to timing extracted from point tracking data recorded with an optical motion capture system.Item Large XML Document Manager and Visualizer(Eurographics Association, 2003) Merienne, J. P.; Jacquemin, C.This work presents an interactive Graphical User Interface used to display and manipulate collection of large XML documents. It relies on a geometrical model that combines hierarchical and sequential representations. In this interface, XML structures are displayed on an inclined plane in a 3D environment. This interface provides users with a visualization that speeds up searches in collection of documents through simple interaction techniques. Document browsing is facilitated through display space optimization and direct manipulation of document structures. Besides, this approach tries to take advantage of 3D by engaging human 3D spatial cognitive capabilities while using 2D interaction to not disrupt user's habits. A user evaluation for document access is reported that shows that our interface tends to be faster than 2D interface in data searching while taking advantage of the user's natural attraction to 3D interface.Item Curve Synthesis from Learned Refinement Models(Eurographics Association, 2003) Simhon, Saul; Dudek, GregoryWe present a method for generating refined 2D illustrations from hand drawn outlines consisting of only curve strokes. The system controllably synthesizes novel illustrations by augmenting the hand drawn curves’ shape, thickness, color and surrounding texture. These refinements are learned from a training ensemble. Users can select several examples that depict the desired idealized look and train the system for that type of refinement. Further, given several types of refinements, our system automatically recognizes the curve and applies the appropriate refinement. Recognition is accomplished by evaluating the likelihood the curve belongs to a particular class based on both its shape and context in the illustration.Item Preface(Eurographics Association, 2003)Item Goniometric Diagram Mapping for Hemisphere(Eurographics Association, 2003) Havran, Vlastimil; Dmitriev, Kirill; Seidel, Hans-PeterDescribing the light intensity over the hemisphere using a goniometric diagram is a common practice in the lighting industry and is prescribed for instance by IESNA (Illuminating Engineering Society of North America) standards. Goniometric diagram specifies the spatial distribution of the emitted power via a hemispherical surface subdivided by meridians and parallels. Similar tabulated representations are extensively used for complex bidirectional refiectance distribution functions (BRDF) that are difficult to approximate with analytical models. We present an approximative bicontinuous mapping from the unit square to a goniometric diagram on the hemisphere. This mapping has low distortion and the error of the approximation is low. The proposed mapping algorithm is obtained as a composition of four mappings. We outline its use for importance sampling of light sources described by goniometric diagrams and for the representation of BRDF.Item Extending the Immediate Buckling Model to Triangular Meshes for Simulating Complex Clothes(Eurographics Association, 2003) Choi, Kwang-Jin; Ko, Hyeong-SeokThe immediate buckling model is an essential element for simulating realistic cloth animations without introducing buckling instability. The original model is restricted to structured regular quad meshes, by which its use is severely limited. This paper extends the immediate buckling model from its original formulation in terms of regular quad meshes to irregular triangular meshes, thereby significantly increasing the applicability of the technique. Using a model that included cloth-specific buckling and anisotropy, we produced realistic animations of quite complex clothes.Item Efficient Sampling of Textured Scenes in Vertex Tracing(Eurographics Association, 2003) Ullmann, Thomas; Preidel, Thomas; Bruderlin, BeatWe present vertex tracing, an adaptive progressive ray tracing approach for efficient sampling of the radiance function, based on refinement in object space and subsequent reconstruction, using standard 3D graphics accelerator hardware. The main focus of this paper is the reconstruction of reflected and transmitted texture maps. By taking advantage of the newest graphics hardware features (such as the pixel shader) even higher levels of recursion can be supported without explicit sampling of the textures. In addition, the graphics hardware is used for an efficient visibility test, which leads to a further reduction of ray samples, and for the rendering of diffuse local illumination effects, as well as for progressive rendering of the global illumination effects, which are superimposed over the hardware-rendered scene in object space. With this approach, interactive performance for realistically rendered illumination effects of scenes of average complexity, can be achieved on a standard PC with off-the-shelf 3D graphics accelerators.Item Real-time Obscurances with Color Bleeding (the three cubes demo)(Eurographics Association, 2003) Méndez, Àlex; Sbert, Mateu; Catà, JordiHere we present an animation that demonstrates the power of the obscurances technique and how it can be used in a video-game context when moving objects are in the scene. Obscurances is a powerful technique that simulates diffuse illumination, i.e. radiosity, with a much lower cost. Its advantage is based in that it considers only neighbour interactions instead of considering global ones, and in being decoupled from direct illumination computation. The implementation of this technique is made on a 3D game engine that allows real-time recomputation of obscurances for moving objects. Extensions to deal with color bleeding can also be appreciated.Item Reconstruction of Animatable Personalized 3D Faces by Adaptation-based Modeling(Eurographics Association, 2003) Zhang, Yu; Sim, Terence; Tan, Chew LimWe present an efficient method for the construction of an animatable 3D facial model of a specific person with minimal user interaction. The method is based on adapting an anatomy-based prototype facial model that is suitable for physically-based facial animation to the geometry of a real persons face recovered from laser-scanned range data. Starting with specification of a set of anthropometric landmarks on the 2D images, we automatically recover the 3D positions of the landmark points on the facial surface. A global shape adaptation is then carried out to align the prototype model to the target geometry using the transformation parameters estimated from measurements between recovered 3D landmark points. A local shape adaptation follows to deform the prototype model for fitting all of its vertices to the scanned surface data. The reconstructed 3D face portrays the geometry and color of the individual face and can be animated immediately with the given muscle parameters.Item Occlusion Culling for Image-Based Rendering withWarping(Eurographics Association, 2003) Soner, I. Sen; Atalay, VolkanThe basic idea of the proposed algorithm is to reduce the number of depth pixels in Layer Depth Images (LDI) by culling the occluded ones before warping. The method combines the octree spatial subdivision concept with LDI concept, using the implicit geometry stored in depth pixels. The algorithm uses an octree to group depth pixels in a hierarchical way. The proposed algorithm is very effective when used in highly occluded scenes, and the density of the depth pixels should be high enough to get a high performance from the algorithmItem Freeform Shape Representations for Efficient Geometry Processing(Eurographics Association, 2003) Kobbelt, LeifThe most important concepts for the handling and storage of freeform shapes in geometry processing applications are parametric representations and volumetric representations. Both have their specific advantages and drawbacks. While the algebraic complexity of volumetric representations is independent from the shape complexity, the domain of a parametric representation usually has to have the same structure as the surface itself (which sometimes makes it necessary to update the domain when the surface is modified). On the other hand, the topology of a parametrically defined surface can be controlled explicitly while in a volumetric representation, the surface topology can change accidentally during deformation. A volumetric representation reduces distance queries or inside/outside tests to mere function evaluations but the geodesic neighborhood relation between surface points is difficult to resolve. As a consequence, it seems promising to combine parametric and volumetric representations to effectively exploit both advantages. In this talk, a number of projects are presented and discussed in which such a combination leads to efficient and numerically stable algorithms for the solution of various geometry processing tasks. Applications include global error control for mesh decimation and smoothing, topology control for level-set surfaces, and shape modeling with unstructured point clouds.Item A Refereed Server for Educational CG Content(Eurographics Association, 2003) Figueiredo, Frederico C.; Eber, Dena E.; Jorge, Joaquim A.Computer graphics has evolved considerably over the past few decades. As computer science, digital arts, and other areas of study that use computer graphics continue to evolve and gain new substance, educators have come to master new content and achieve deeper understandings of computers and imagery. As the core field becomes more mature, educators in all computer graphics disciplines have a greater need for high-quality curricular resources. Offering excellent educational materials is an important service to the community of educators. Such support will empower both young and seasoned educators alike to benefit from and contribute to the work of others. In this way, we can achieve a higher standard of teaching worldwide. The purpose of our work is to provide tools to foster such a community of computer graphics educators. We will present a system that will act as the means for their work to be appraised, assessed and made available to others through an online server for refereed educational content in computer graphics. In this paper we describe the basis for and highlight some of the starting requirements of CGEMS, the online Computer Graphics Educational Materials Server. This is organized around a web-based groupware application that supports the submission, review, acquisition, and archiving of curricular resources.Item Trans-Polygon Stroke Method for Frame Coherent Pastel Images(Eurographics Association, 2003) Murakami, Kyoko; Tsuruno, ReijiWe propose Trans-Polygon Stroke Method (TPSM) for creating pastel-like animation that keeps frame-to-frame coherence. There are several variable factors in hand-drawn pastel such as paper roughness and pigments. When these factors are simulated in computer graphics animation, they cause flickers, which reduces visibility. To increase the visibility of pastel-like animation by reducing the flickers, it is need to fix the factors. The procedure of the TPSM is to (1) model objects with quadrilateral polygons, (2) generate particles on the polygons, (3) give a vector direction to each particle, and (4) draw a line from the particle to the n-th polygon along with the direction. Besides the TPSM, the amount of pigments used for one stroke is read from a given table to fix this variable factor. We demonstrate several types of drawn strokes, such as hatching, stipple, and blending, using the proposed method.Item Particle-based Collision Detection(Eurographics Association, 2003) Senin, Mikhail; Nikita, Kojekine; Savchenko, Vladimir; Hagiwara, IchiroIn the paper we present a novel algorithm for collision detection between complex geometric objects represented by polygonal models and undergoing rigid motions and deformations. Most algorithms described in the literature deal with rigid bodies and are based on some kind of hierarchical representations. We present the alternative approach. The algorithm relies on the idea of "sensor particles": interacting particles distributed on a surface. Two types of particles that interact in a special way are used for determining the minimum distance between two models. The algorithm has been implemented and used in real time simulation of dynamic interaction between geometric objects. A detailed description of the algorithm, animation examples, and benchmarks are included in the paper. A potential application of this software algorithm is collision detection for animation of bodies with deformable surfaces.Item ActiveInk(Eurographics Association, 2003) Tobita, Hiroaki; Rekimoto, JunThe ActiveInk system integrates the advantages of real world painting techniques with computer graphics (CG) effects such as natural phenomenon animations (e.g., water, fire, snow, and clouds), attributes (e.g., rubber, cloth, and land), surface materials (e.g., texture effects, metal, and glass), and so on. Most conventional paint systems mainly allow users to set a simple and static color. Also, they require users to control many parameters if the user applies complex effects. However, the ActiveInk system treats many behaviors as separate behavior inks (e.g., water, cloud, and cloth ink), so a user can add effects by selecting a behavior ink and painting it onto objects to realize CG effects. Moreover, the system has a palette area that is similar in function to an actual painters palette, so the user can create a new ink by mixing different types of behavior ink and can control the behavior in the palette area directly. In this paper, we describe a prototype of the ActiveInk system, explain how it allows CG effects to be applied through simple and easy manipulations, and discuss its implementation.