23-Issue 3

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/10150

Browse

Now showing 1 - 20 of 47

Quadric Transfer for Immersive Curved Screen Displays
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Raskar, Ramesh; van Baar, Jeroen; Willwacher, Thomas; Rao, Srinivas
Curved screens are increasingly being used for high-resolution immersive visualization environments. We describe a new technique to display seamless images using overlapping projectors on curved quadric surfaces such as spherical or cylindrical shape. We exploit a quadric image transfer function and show how it can be used to achieve sub-pixel registration while interactively displaying two or three-dimensional datasets for a head-tracked user. Current techniques for automatically registered seamless displays have focused mainly on planar displays. On the other hand, techniques for curved screens currently involve cumbersome manual alignment to make the installation conform to the intended design. We show a seamless real-time display system and discuss our methods for smooth intensity blending and efficient rendering.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism- Virtual reality
Real-time Rigid Body Simulation for Haptic Interactions Based on Contact Volume of Polygonal Objects
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Hasegawa, S.; Sato, M.
This paper proposes a new method for real-time rigid body simulations for haptic interactions based on a penalty method regarding contact volume. Analytical methods for calculation of contact forces require too much time to maintain fast update rates for haptic controls. In addition, they prohibit direct connection of haptic interfaces.Penalty methods, which employ spring-damper models for calculation of contact forces, offer a very rapid rate of iterations. In addition, they permit direct connection of haptic interfaces. Penalty methods are good for haptic interactions. However, previous penalty methods do not regard distribution of contact forces over the contact area. For that reason, they can't calculate normal and friction forces on face-face contacts correctly.We propose a distributed spring-damper model on a contact area to solve these problems. We analyze three-dimensional geometries of the intersecting portion on the polyhedral objects. Then, we integrate forces and torques of distributed spring-damper models.We implement a proposed simulator and compare it with a point-based penalty method and constraint method. The comparison shows that the proposed simulator improves accuracy of the simulation of face-face contact and friction forces and the simulation speed. In addition, we attach a six degree-of-freedom (6-DOF) haptic interface to the simulator. Users can feel 6-DOF force feedback and input 6-DOF motions.Categories and Subject Descriptors (according to ACM CCS): I.6.5 [Model Development]: Modeling methodologies, H.5.2 [User Interfaces]: Haptic I/O, I.3.6 [Methodology and Techniques]: Interaction techniques
Interference Detection for Subdivision Surfaces
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Wu, Xiaobin; Peters, Joerg
Accurate and robust interference detection and ray-tracing of subdivision surfaces requires safe linear approximations. Approximation of the limit surface by the subdivided control polyhedron can be both inaccurate and, due to the exponential growth of the number of facets, costly.This paper shows how a standard intersection hierarchy, such as an OBB tree, can be made safe and efficient for subdivision surface interference detection. The key is to construct, on the fly, optimally placed facets, whose spherical offsets tightly enclose the limit surface. The spherically offset facets can be locally subdivided and they can be efficiently intersected based on standard triangle-triangle interference detection.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling
Implicit Visualization and Inverse Modeling of Growing Trees
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Galbraith, Callum; Muendermann, Lars; Wyvill, Brian
A method is proposed for photo-realistic modeling and visualization of a growing tree. Recent visualization methods have focused on producing smoothly blending branching structures, however, these methods fail to account for the inclusion of non-smooth features such as branch bark ridges and bud scale scars. These features constitute an important visual aspect of a living tree, and are also observed to vary over time. The proposed method incorporates these features by using an hierarchical implicit modeling system, which provides a variety of tools for combining surface components in both smooth and non smooth configurations. A procedural interface to this system supports the use of inverse modeling, which is a global-to-local methodology, where the local properties of plant organs are described in terms of their global position within the tree architecture. Inverse modeling is used to define both the tree structure at any time, and a continuous developmental sequence for the tree from a seedling. These techniques provide an intuitive paradigm for the definition of complex tree growth sequences and their subsequent visualization, based solely on observed phenomena. Thus, a key advantage is that they do not require any knowledge of, or simulation of, the underlying biological processes.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Curve, surface, solid, and object representations I.3.7 [Computer Graphics]: Animation
Crowd of Virtual Humans: a New Approach for Real Time Navigation in Complex and Structured Environments
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Lamarche, Fabrice; Donikian, Stephane
The navigation activity is an every day practice for any human being capable of locomotion. Our objective in this work is to reproduce this crucial human activity inside virtual environments. Putting together the high complexity of a realistic environment such as a city, a big amount of virtual humans and the real-time constraint requires to optimize each aspect of the animation process. In this paper, we present a suitable topological structuring of the geometric environment to allow fast path finding as well as an efficient reactive navigation algorithm for virtual humans evolving inside a crowd.
The Design of an Inexpensive Very High Resolution Scan Camera System
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Wang, Shuzhen; Heidrich, Wolfgang
Balancing Considered Harmful - Faster Photon Mapping using the Voxel Volume Heuristic -
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Wald, Ingo; Guenther, Johannes; Slusallek, Philipp
Photon mapping is one of the most important algorithms for computing global illumination. Especially for efficiently producing convincing caustics, there are no real alternatives to photon mapping. On the other hand, photon mapping is also quite costly: Each radiance lookup requires to find the k nearest neighbors in a kd-tree, which can be more costly than shooting several rays. Therefore, the nearest-neighbor queries often dominate the rendering time of a photon map based renderer.In this paper, we present a method that reorganizes - i.e. un balances - the kd-tree for storing the photons in a way that allows for finding the k-nearest neighbors much more efficiently, thereby accelerating the radiance estimates by a factor of 1.2-3.4. Most importantly, our method still finds exactly the same k-nearest-neighbors as the original method, without introducing any approximations or loss of accuracy. The impact of our method is demonstrated with several practical examples.Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Global Illumination I.3.7 [Computer Graphics]: Raytracing
Scalable behaviors for crowd simulation
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Sung, Mankyu; Gleicher, Michael; Chenney, Stephen
Crowd simulation for virtual environments offers many challenges centered on the trade-offs between rich behavior, control and computational cost. In this paper we present a new approach to controlling the behavior of agents in a crowd. Our method is scalable in the sense that increasingly complex crowd behaviors can be created without a corresponding increase in the complexity of the agents. Our approach is also more authorable; users can dynamically specify which crowd behaviors happen in various parts of an environment. Finally, the character motion produced by our system is visually convincing. We achieve our aims with a situation-based control structure. Basic agents have very limited behaviors. As they enter new situations, additional, situation-specific behaviors are composed on the fly to enable agents to respond appropriately. The composition is done using a probabilistic mechanism. We demonstrate our system with three environments including a city street and a theater.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Animation
Procedural Texture Matching and Transformation
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Bourque, Eric; Dudek, Gregory
We present a technique for creating a smoothly varying sequence of procedural textures that interpolates between arbitrary input samples of texture. This texture transformation uses a library of procedural shaders and selects the correct shaders and associated parameters to accomplish the task.In general, selecting a procedural texture from a library, or finding the correct parameters to produce a smooth texture transition can be complex and time consuming. We propose a strategy for automating this process. While superficially this problem appears intractable for both humans and computational systems, its natural characteristics make a computational solution feasible. We present an algorithm and experimental results demonstrating this approach.Transformation between two textures can then be achieved procedurally, while enforcing perceptual similarity constraints between adjacent texture frames. We describe a technique for efficiently sampling the parameter domain of a shader based on a texture similarity function to create a smooth path through its texture range. In the case of evolving between several shaders, a method is described to obtain the best jump-points which can be used to connect different shaders smoothly in texture space. Several examples of the technique are shown, and future directions as well as potential problems are discussed.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Texture
Single-Strip Triangulation of Manifolds with Arbitrary Topology
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Gopi, M.; Eppstien, David
Anisotropic Filtering of Non-Linear Surface Features
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Hildebrandt, Klaus; Polthier, Konrad
A new method for noise removal of arbitrary surfaces meshes is presented which focuses on the preservation and sharpening of non-linear geometric features such as curved surface regions and feature lines. Our method uses a prescribed mean curvature flow (PMC) for simplicial surfaces which is based on three new contributions: 1. the definition and efficient calculation of a discrete shape operator and principal curvature properties on simplicial surfaces that is fully consistent with the well-known discrete mean curvature formula, 2. an anisotropic discrete mean curvature vector that combines the advantages of the mean curvature normal with the special anisotropic behaviour along feature lines of a surface, and 3. an anisotropic prescribed mean curvature flow which converges to surfaces with an estimated mean curvature distribution and with preserved non-linear features. Additionally, the PMC flow prevents boundary shrinkage at constrained and free boundary segments.
Synthesizing Sound from Turbulent Field using Sound Textures for Interactive Fluid Simulation
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Dobashi, Yoshinori; Yamamoto, Tsuyoshi; Nishita, Tomoyuki
Sound is an indispensable element for the simulation of a realistic virtual environment. Therefore, there has been much recent research focused on the simulation of realistic sound effects. This paper proposes a method for creating sound for turbulent phenomena such as fire. In a turbulent field, the complex motion of vortices leads to the generation of sound. This type of sound is called a vortex sound. The proposed method simulates a vortex sound by computing vorticity distributions using computational fluid dynamics. Sound textures for the vortex sound are first created in a pre-process step. The sound is then created at interactive rates by using these sound textures. The usefulness of the proposed method is demonstrated by applying it to the simulation of the sound of fire and other turbulent phenomena.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism - Animation; I.6.8 [Simulation and Modeling]: Types of Simulation - Animation; I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism; I.6.3 [Simulation and Modeling]: Applications; H.5.5 [Information Interfaces and Presentation]: Sound and Music Computing - Methodologies and techniques, Modeling.
GPU-Based Nonlinear Ray Tracing
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Weiskopf, Daniel; Schafhitzel, Tobias; Ertl, Thomas
In this paper, we present a mapping of nonlinear ray tracing to the GPU which avoids any data transfer back to main memory. The rendering process consists of the following parts: ray setup according to the camera parameters, ray integration, ray-object intersection, and local illumination. Bent rays are approximated by polygonal lines that are represented by textures. Ray integration is based on an iterative numerical solution of ordinary differential equations whose initial values are determined during ray setup. To improve the rendering performance, we propose acceleration techniques such as early ray termination and adaptive ray integration. Finally, we discuss a variety of applications that range from the visualization of dynamical systems to the general relativistic visualization in astrophysics and the rendering of the continuous refraction in media with varying density.Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Picture/Image Generation I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism
Real-time Light Animation
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Sbert, Mateu; Szecsi, Laszlo; Szirmay-Kalos, Laszlo
Light source animation is a particularly hard field of real-time global illumination algorithms since moving light sources result in drastic illumination changes and make coherence techniques less effective. However, the animation of small (point-like) light sources represents a special but practically very important case, for which the reuse of the results of other frames is possible. This paper presents a fast light source animation algorithm based on the virtual light sources illumination method. The speed up is close to the length of the animation, and is due to reusing paths in all frames and not only in the frame where they were obtained. The possible applications of this algorithm are the lighting design and systems to convey shape and features with relighting.
Approximated Centroidal Voronoi Diagrams for Uniform Polygonal Mesh Coarsening
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Valette, Sebastien; Chassery, Jean-Marc
We present a novel clustering algorithm for polygonal meshes which approximates a Centroidal Voronoi Diagram construction. The clustering provides an efficient way to construct uniform tessellations, and therefore leads to uniform coarsening of polygonal meshes, when the output triangulation has many fewer elements than the input mesh. The mesh topology is also simplified by the clustering algorithm. Based on a mathematical framework, our algorithm is easy to implement, and has low memory requirements. We demonstrate the efficiency of the proposed scheme by processing several reference meshes having up to 1 million triangles and very high genus within a few minutes on a low- end computer.
Computing Maximal Tiles and Application to Impostor-Based Simplification
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Andujar, C.; Brunet, P.; Chica, A.; Navazo, I.; Rossignac, J.; Vinacua, A.
The computation of the largest planar region approximating a 3D object is an important problem with wide applications in modeling and rendering. Given a voxelization of the 3D object, we propose an efficient algorithm to solve a discrete version of this problem. The input of the algorithm is the set of grid edges connecting the interior and the exterior of the object (called sticks). Using a voting-based approach, we compute the plane that slices the largest number of sticks and is orientation-compatible with these sticks. The robustness and efficiency of our approach rests on the use of two different parameterizations of the planes with suitable properties. The first of these is exact and is used to retrieve precomputed local solutions of the problem. The second one is discrete and is used in a hierarchical voting scheme to compute the global maximum. This problem has diverse applications that range from finding object signatures to generating simplified models. Here we demonstrate the merits of the algorithm for efficiently computing an optimized set of textured impostors for a given polygonal model.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling
Hierarchical Retargetting of Fine Facial Motions
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Na, Kyunggun; Jung, Moonryul
We present a novel technique for retargetting captured facial animation to new facial models. We use dense motion data that can express fine motions such as wrinkles. We use a normal mesh, which is a special multi-resolution mesh, to represent source and target models. A normal mesh is defined by the base mesh and sequence of normal offsets from it. Our retargetting consists of two steps: base mesh and detail mesh retargetting. For base mesh retargetting, we use an example-based technique to take advantage of the intuition of the user in specifying the similarity between source and target expressions. In detail mesh retargetting, the variations of normal offsets in the source mesh are hierarchically computed and transferred to the target mesh. Our retargetting scheme is able to produce robust and delicate results for unusual target models from highly detailed motion data.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three Dimensional Graphics and Realism - Animation; I.3.5 [Computer Graphics]: Computational Geometry and Object Modelling - hierarchy and geometric transformation, object hierarchy
Topological Construction and Visualization of Higher Order 3D Vector Fields
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Weinkauf, Tino; Theisel, Holger; Hege, Hans-Christian; Seidel, Hans-Peter
We present the first algorithm for constructing 3D vector fields based on their topological skeleton. The skeleton itself is modeled by interactively moving a number of control polygons. Then a piecewise linear vector field is automatically constructed which has the same topological skeleton as modeled before. This approach is based on a complete segmentation of the areas around critical points into sectors of different flow behavior. Based on this, we present the first approach to visualizing higher order critical points of 3D vector fields.Categories and Subject Descriptors (according to ACM CCS): I.3.3 [Computer Graphics]: Line and Curve Generation I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism
High Resolution Acquisition, Learning and Transfer of Dynamic 3-D Facial Expressions
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Wang, Yang; Huang, Xiaolei; Lee, Chan-Su; Zhang, Song; Li, Zhiguo; Samaras, Dimitris; Metaxas, Dimitris; Elgammal, Ahmed; Huang, Peisen
Synthesis and re-targeting of facial expressions is central to facial animation and often involves significant manual work in order to achieve realistic expressions, due to the difficulty of capturing high quality dynamic expression data. In this paper we address fundamental issues regarding the use of high quality dense 3-D data samples undergoing motions at video speeds, e.g. human facial expressions. In order to utilize such data for motion analysis and re-targeting, correspondences must be established between data in different frames of the same faces as well as between different faces. We present a data driven approach that consists of four parts: 1) High speed, high accuracy capture of moving faces without the use of markers, 2) Very precise tracking of facial motion using a multi-resolution deformable mesh, 3) A unified low dimensional mapping of dynamic facial motion that can separate expression style, and 4) Synthesis of novel expressions as a combination of expression styles. The accuracy and resolution of our method allows us to capture and track subtle expression details. The low dimensional representation of motion data in a unified embedding for all the subjects in the database allows for learning the most discriminating characteristics of each individual's expressions as that person's 'expression style'. Thus new expressions can be synthesized, either as dynamic morphing between individuals, or as expression transfer from a source face to a target face, as demonstrated in a series of experiments.Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Animation; I.3.5 [Computer Graphics]: Curve, surface, solid, and object representations; I.3.3 [Computer Graphics]: Digitizing and scanning; I.2.10 [Artificial intelligence]: Motion ; I.2.10 [Artificial intelligence]: Representations, data structures, and transforms; I.2.10 [Artificial intelligence]: Shape; I.2.6 [Artificial intelligence]: Concept learning
Instant Volumetric Understanding with Order-Independent Volume Rendering
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Mora, Benjamin; Evert, David S.
Rapid, visual understanding of volumetric datasets is a crucial outcome of a good volume rendering application, but few current volume rendering systems deliver this result. Our goal is to reduce the volumetric surfing that is required to understand volumetric features by conveying more information in fewer images. In order to achieve this goal, and in contrast with most current methods which still use optical models and alpha blending, our approach reintroduces the order-independent contribution of every sample along the ray in order to have an equiprobable visualization of all the volume samples. Therefore, we demonstrate how order independent sampling can be suitable for fast volume understanding, show useful extensions to MIP and X-ray like renderings, and, finally, point out the special advantage of using stereo visualization in these models to circumvent the lack of depth cues.Categories and Subject Descriptors: I.3.3 [Computer Graphics]: Picture/Image, Generation,I.3.7 [Computer Graphics]: Three-Dimensional graphics and realism.

Browse

Browsing 23-Issue 3 by Issue Date

Results Per Page

Sort Options