Volume 22 (2003)
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Item Efficient Modeling of An Anatomy-Based Face and Fast 3D Facial Expression Synthesis(Blackwell Publishers, Inc and the Eurographics Association, 2003) Zhang, Yu; Prakash, Edmond C.; Sung, EricThis paper presents new methods for efficient modeling and animation of an hierarchical facial model that conforms to the human face anatomy for realistic and fast 3D facial expression synthesis. The facial model has a skin-muscle-skull structure. The deformable skin model directly simulates the nonlinear visco-elastic behavior of soft tissue and effectively prevents model collapse. The construction of facial muscles is achieved by using an efficient muscle mapping approach. Based on a cylindrical projection of the texture-mapped facial surface and wire-frame skin and skull meshes, this approach ensures different muscles to be located at the anatomically correct positions between the skin and skull layers. For computational efficiency, we devise an adaptive simulation algorithm which uses either a semi-implicit integration scheme or a quasi-static solver to compute the relaxation by traversing the designed data structures in a breadth-first order. The algorithm runs in real-time and has successfully synthesized realistic facial expressions.ACM CSS: I.3.5 Computer Graphics: Computational Geometry and Object Modelling-physically based modelling; I.3.7 Computer Graphics: Three-Dimensional Graphics and Realism-animation;Item Join Now!(Blackwell Publishers, Inc and the Eurographics Association, 2003)Item Fast Photo-Realistic Rendering of Trees in Daylight(Blackwell Publishers, Inc and the Eurographics Association, 2003) Qin, Xueying; Nakamae, Eihachiro; Tadamura, Katsumi; Nagai, YasuoWe propose a fast approach for photo-realistic rendering of trees under various kinds of daylight, which is particularlyuseful for the environmental assessment of landscapes. In our approach the 3D tree models are transformedto a quasi-3D tree database registering geometrical and shading information of tree surfaces, i.e. their normalvectors, relative depth, and shadowing of direct sunlight and skylight, by using a combination of 2D buffers.Thus the rendering speed of quasi-3D trees depends on their display sizes only, regardless of the complexity oftheir original 3D tree models. By utilizing a two-step shadowing algorithm, our proposed method can create highquality forest scenes illuminated by both sunlight and skylight at a low cost. It can generate both umbrae andpenumbrae on a tree cast by other trees and any other objects such as buildings or clouds. Transparency, specularreflection and inter-reflection of leaves, which influence the delicate shading effects of trees, can also be simulatedwith verisimilitude.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three dimensional Graphics and RealismItem The State of the Art in Flow Visualisation: Feature Extraction and Tracking(Blackwell Publishing, Inc and Eurographics Association, 2003) Post, Frits H.; Vrolijk, Benjamin; Hauser, Helwig; Laramee, Robert S.; Doleisch, HelmutFlow visualisation is an attractive topic in data visualisation, offering great challenges for research. Very large data sets must be processed, consisting of multivariate data at large numbers of grid points, often arranged in many time steps. Recently, the steadily increasing performance of computers again has become a driving force for new advances in flow visualisation, especially in techniques based on texturing, feature extraction, vector field clustering, and topology extraction.In this article we present the state of the art in feature-based flow visualisation techniques. We will present numerous feature extraction techniques, categorised according to the type of feature. Next, feature tracking and event detection algorithms are discussed, for studying the evolution of features in time-dependent data sets. Finally, various visualisation techniques are demonstrated.ACM CSS: I.3.8 Computer Graphics-applicationsItem Rendering and Affect(Blackwell Publishers, Inc and the Eurographics Association, 2003) Duke, D.J.; Barnard, P.J.; Halper, N.; Mellin, M.Previous studies at the intersection between rendering and psychology have concentrated on issues such as realismand acuity. Although such results have been useful in informing development of realistic rendering techniques,studies have shown that the interpretation of images is influenced by factors that have little to do with realism. Inthis paper, we summarize a series of experiments, the most recent of which are reported in a separate paper, thatinvestigate affective (emotive) qualities of images. These demonstrate significant effects that can be utilized withininteractive graphics, particularly via non-photorealistic rendering (NPR). We explain how the interpretation ofthese results requires a high-level model of cognitive information processing, and use such a model to account forrecent empirical results on rendering and judgement.Categories and Subject Descriptors (according to ACM CCS): I.3.m [Computer Graphics]: MiscellaneousItem Auditor-s Report(Blackwell Publishing, Inc and Eurographics Association, 2003)Item Recent Developments and Applications of Haptic Devices(Blackwell Publishers, Inc and the Eurographics Association, 2003) Laycock, S. D.; Day, A. M.Over recent years a variety of haptic feedback devices have been developed and are being used in a number of important applications. They range from joysticks used in the entertainment industry to specialised devices used in medical applications. This paper will describe the recent developments of these devices and show how they have been applied. It also examines how haptic feedback has been combined with visual display devices, such as virtual reality walls and workbenches, in order to improve the immersive experience.ACM CSS: H.5.2 Information Interfaces and Presentation-Haptic I/O; I.3.8 Computer Graphics-Applications; I.6 Simulation and Modelling-ApplicationsItem Interactive Rendering with Bidirectional Texture Functions(Blackwell Publishers, Inc and the Eurographics Association, 2003) Suykens, Frank; Berge, Karl; Lagae, Ares; Dutre, PhilipWe propose a new technique for efficiently rendering bidirectional texture functions (BTFs). A 6D BTF describesthe appearance of a material as a texture that depends on the lighting and viewing directions. As such, a BTFaccommodates self-shadowing, interreflection, and masking effects of a complex material without needing anexplicit representation of the small scale geometry. Our method represents the BTF as a set of spatially varyingapparent BRDFs, that each encode the reflectance field of a single pixel in the BTF. Each apparent BRDF isdecomposed into a product of three or more two-dimensional positive factors using a novel factorization technique,which we call chained matrix factorization (CMF). The proposed factorization technique is fully automatic andsuitable for both BRDFs and apparent BRDFs (which typically exhibit off-specular peaks and non-reciprocity).The main benefit of CMF is that it delivers factors well suited for the limited dynamic range of conventionaltexture maps. After factorization, an efficient representation of the BTF is obtained by clustering the factors intoa compact set of 2D textures. With this compact representation, BTFs can be rendered on recent consumer levelhardware with arbitrary viewing and lighting directions at interactive rates.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three-DimensionalGraphics and RealismItem Fourth Eurographics Workshop on Parallel Graphics and Visualisation(Blackwell Publishers, Inc and the Eurographics Association, 2003) Reinhard, ErikItem Field Functions for Blending Range Controls on Soft Objects(Blackwell Publishers, Inc and the Eurographics Association, 2003) Hsu, P. C.; Lee, C.This paper proposes new field functions that have adjustable inner radius and outer radius of influence. Incorporatingthe proposed field functions with soft object modeling, soft blending, Ricci's super-ellipsoid blends, Perlin'sset operations, and R-functions, etc. can have blending range controls by adjusting the inner and the outer radiiof influence of given field functions. As a result, the sizes of the resulting blending surfaces on soft objects willnot be restricted by the sizes of the blended primitive soft objects and can be enlarged and shrunk freely withoutdeforming the overall shapes of blended primitive soft objects. In addition, a small soft object can have a largeblending region, and a large one can have a small blending regionCategories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling - Curve, surface, solid and object representationsItem Narrative Use of Sign Language by a Virtual Character for the Hearing Impaired(Blackwell Publishers, Inc and the Eurographics Association, 2003) Rieger, Thomas; Braun, NorbertThis paper describes the concept and control of a 3d virtual character system with facial expressions and gesturesas a conversational user interface with narrative expressiveness for the hearing impaired. The gestures and facialexpressions are based on morphing techniques. The system allows the generation of sign language and mouthmotion in real time from text at the level of lip reading quality. The concept of Narrative Extended Speech Acts(NESA) is introduced, based on Interactive Storytelling techniques and the concepts of Narrative Conflict andSuspense Progression. We define a choice of annotation tags to be used with NESAs. We use the NESAs to classifyconversation fragments and to enhance computer generated sign language. We note, how the sign language gesturesare generated and show the possibilities for editing sign language gestures. Furthermore, we give details onhow the NESAs are mapped to gestures. We show the possibilities of controlling the virtual character's behaviourand gestures in a human-oriented way and provide an outlook on future work.Categories and Subject Descriptors (according to ACM CCS): 1.3.6 [Computer Graphics]: Methodology and TechniquesItem COMPUTER GRAPHICS forum(Blackwell Publishers, Inc and the Eurographics Association, 2003)Eurographics and Computer Graphics forum offer a variety of services on the international networks. You can find details of our latest events, how to prepare a paper for the conference or for the journal and much more besides. This information can be accessed mainly through the EG website but we also offer some support for ftp and mail server access.Item Interactive Cutaway Illustrations(Blackwell Publishers, Inc and the Eurographics Association, 2003) Diepstraten, J.; Weiskopf, D.; Ertl, T.In this paper we discuss different approaches to generate cutaway illustrations. The purpose of such a drawingis to allow the viewer to have a look into an otherwise solid opaque object. Traditional methods to draw thesekinds of illustrations are evaluated to extract a small and effective set of rules for a computer-based renderingof cutaway illustrations. We show that our approaches are not limited to a specific rendering style but can besuccessfully combined with a great variety of well-known artistic or technical illustration techniques. All methodsof this paper make use of modern graphics hardware functionality to achieve interactive frame rates.Item Particle-Based Simulation of Fluids(Blackwell Publishers, Inc and the Eurographics Association, 2003) Premzoe, Simon; Tasdizen, Tolga; Bigler, James; Lefohn, Aaron; Whitaker, Ross T.Due to our familiarity with how fluids move and interact, as well as their complexity, plausible animation of fluidsremains a challenging problem. We present a particle interaction method for simulating fluids. The underlyingequations of fluid motion are discretized using moving particles and their interactions. The method allows simulationand modeling of mixing fluids with different physical properties, fluid interactions with stationary objects, andfluids that exhibit significant interface breakup and fragmentation. The gridless computational method is suitedfor medium scale problems since computational elements exist only where needed. The method fits well into thecurrent user interaction paradigm and allows easy user control over the desired fluid motion.Item Creation and Control of Real-time Continuous Level of Detail on Programmable Graphics Hardware(Blackwell Publishers, Inc and the Eurographics Association, 2003) Southern, Richard; Gain, JamesContinuity in level of detail sequences is essential in hiding visual artefacts that occur when switching between discrete levels of detail. However, construction and implementation of these sequences is prohibitively complex. We present a new structure, the g-mesh, which greatly simplifies the implementation of continuous level of detail in large scenes. We also introduce a novel greedy predictive level of detail control system suited to the g-mesh. Finally we achieve a dramatic improvement in the rendering of morphing sequences by exploiting current graphics hardware.ACM CSS: I.3.5 Computational Geometry and Object Modeling-Geometric Transformations, Object Hierarchies, I.3.6 Methodology and Techniques-Graphics Data StructuresItem A Scalable Approach to Interactive Global Illumination(Blackwell Publishers, Inc and the Eurographics Association, 2003) Benthin, Carsten; Wald, Ingo; Slusallek, PhilippThe addition of global illumination can dramatically increase the realism achievable when rendering virtual environments.In particular with interactive applications we expect the environment to reflect changes in the scenedue to global lighting effects instead of it being just a static backdrop. However, a sufficiently fast and accuratecomputation of global illumination at interactive rates has been difficult even with recent approaches based onrealtime ray tracing.In this paper we present a highly scalable approach to interactive global illumination. It fully recomputes a high-qualitysolution for each frame and thus offers immediate feedback even for dynamic scenes, achieving more than20 fps for simple scenes. Compared to previous systems we increased the raw performance by a factor of up toeight and removed the bottlenecks that were limiting scalability. The system now scales linearly in quality andavailable computing resources, tested with up to 48 CPUs in a commodity PC-cluster. Due to its logarithmicscaling property with respect to scene complexity it even supports lighting simulation in complex scenes with morethan 50 million triangles. This scalability allows applications to perform flexible performance trade-offs. We alsoargue that the realism achievable through interactive global illumination will make it a standard feature of future3D graphics systems once the required computing resources are readily available.Item Hierarchical Context-based Pixel Ordering(Blackwell Publishers, Inc and the Eurographics Association, 2003) Bar-Joseph, Ziv; Cohen-Or, DanielWe present a context-based scanning algorithm which reorders the input image using a hierarchical representationof the image. Our algorithm optimally orders (permutes) the leaves corresponding to the pixels, by minimizing thesum of distances between neighboring pixels. The reordering results in an improved autocorrelation betweennearby pixels which leads to a smoother image. This allows us, for the first time, to improve image compressionrates using context-based scans. The results presented in this paper greatly improve upon previous work in bothcompression rate and running time.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometryand Object Modeling I.3.6 [Computer Graphics]: Methodology and TechniquesItem A Fast Rendering Method for Refractive and Reflective Caustics Due to Water Surfaces(Blackwell Publishers, Inc and the Eurographics Association, 2003) Iwasaki, Kei; Dobashi, Yoshinori; Nishita, TomoyukiIn order to synthesize realistic images of scenes that include water surfaces, the rendering of optical effectscaused by waves on the water surface, such as caustics and reflection, is necessary. However, rendering causticsis quite complex and time-consuming. In recent years, the performance of graphics hardware has made significantprogress. This fact encourages researchers to study the acceleration of realistic image synthesis. We present herea method for the fast rendering of refractive and reflective caustics due to water surfaces. In the proposed method,an object is expressed by a set of texture mapped slices. We calculate the intensities of the caustics on the objectby using the slices and store the intensities as textures. This makes it possible to render caustics at interactive rateby using graphics hardware. Moreover, we render objects that are reflected and refracted due to the water surfaceby using reflection/refraction mapping of these slices.Categories and Subject Descriptors (according to ACM CCS): I.3.1 [Computer Graphics]: Hardware Architecture I.3.7 [Computer Graphics]: Three-Dimensional Graphics and RealismItem Siggraph 2003(Blackwell Publishing, Inc and Eurographics Association, 2003) Laycock, S. D.; Laycock, R. G.Item Adaptive Ray Tracing of Subdivision Surfaces(Blackwell Publishers, Inc and the Eurographics Association, 2003) Müller, Kerstin; Techmann, Torsten; Fellner, Dieter W.Subdivision Surfaces as well as (interactive) ray tracing have become an important issue in computer graphics.But ray tracing of subdivision surfaces has received only little attention. We present a new approach for raytracing of subdivision surfaces. The algorithm uses a projection of the ray onto the surface and works mainly intwo dimensions along this projection. While proceeding from patch to patch, we examine the bounding volume oftheir borders: the lower the distance between ray and subdivision surface, the more refinement steps are adaptivelyapplied to the surface but only along the projection of the ray. The adaptive refinement of a patch is controlled bycurvature, size, its membership to the silhouette, and its potential contribution to the light transport. The algorithmis simple and mainly consists of elementary geometric computations. Hence it is fast and easy to implementwithout the need for elaborate preprocessing. The algorithm is robust in the sense that it deals with all features ofsubdivision surfaces like creases and corners.Categories and Subject Descripters (according to ACM CCS): I.3.7 [Computer Graphics]: Raytracing