Volume 23 (2004)

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Network Service
(2004)
Image Interpolation by Pixel-Level Data-Dependent Triangulation
(The Eurographics Association and Blackwell Publishing Ltd., 2004) Su, Dan; Willis, Philip
We present a novel image interpolation algorithm. The algorithm can be used in arbitrary resolution enhancement, arbitrary rotation and other applications of still images in continuous space. High-resolution images are interpolated from the pixel-level data-dependent triangulation of lower-resolution images. It is simpler than other methods and is adaptable to a variety of image manipulations. Experimental results show that the new 'mesh image' algorithm is as fast as the bilinear interpolation method. We assess the interpolated images' quality visually and also by the MSE measure which shows our method generates results comparable in quality to slower established methods. We also implement our method in graphics card hardware using OpenGL which leads to real-time high-quality image reconstruction. These features give it the potential to be used in gaming and image-processing applications.
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
Fast Multipath Radiosity using Hierarchical Subscenes
(The Eurographics Association and Blackwell Publishing Ltd., 2004) Castro, F.; Sbert, M.; Neumann, L.
This paper presents an efficient acceleration technique for the global line radiosity Multipath method. In this approach, the scene is subdivided in a hierarchy of box bounded subscenes, the boxes subdivided in a grid of virtual patches which store angular information. A new recursive (according to the hierarchy of subscenes) function allows to execute the Multipath algorithm at different levels of the hierarchy. A speed up factor up to 3-4 has been obtained on some of the tested scenes.
Placement of Deformable Objects
(The Eurographics Association and Blackwell Publishing Ltd., 2004) S. Schein; G. Elber
With the increasing complexity of photorealistic scenes, the question of building and placing objects in three-dimensional scenes is becoming ever more difficult. While the question of placement of rigid objects has captured the attention of researchers in the past, this work presents an intuitive and interactive scheme to properly place deformable objects with the aid of free-form deformation tools. The presented scheme can also be used to animate the locomotion of nonrigid objects, most noticeably animals, and adapt the motion to arbitrary terrain. The automatic construction of our free-form deformation tool is completely hidden from the end user, and hence, circumvents the difficulties typically faced in manipulating these deformation functions. Further, a precise bound on the error that is introduced by applying free-form deformations to polygonal models is presented, along with an almost-optimal adaptive refinement algorithm to achieve a certain accuracy in the mapping.
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
Siggraph 2004
(The Eurographics Association and Blackwell Publishing Ltd., 2004) Laycock, S. D.; Laycock, R. G.; Ryder, G.; Juarez-Comboni, J.; Montes de Oca, C.
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
Computer Graphics forum
(The Eurographics Association and Blackwell Publishing, Inc, 2004) Duke, David; Scopigno, Roberto
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
The State of the Art in Flow Visualization: Dense and Texture-Based Techniques
(The Eurographics Association and Blackwell Publishing Ltd., 2004) Laramee, Robert S.; Hauser, Helwig; Doleisch, Helmut; Vrolijk, Benjamin; Post, Frits H. and Weiskopf, Daniel
Flow visualization has been a very attractive component of scientific visualization research for a long time. Usually very large multivariate datasets require processing. These datasets often consist of a large number of sample locations and several time steps. The steadily increasing performance of computers has recently become a driving factor for a reemergence in flow visualization research, especially in texture-based techniques. In this paper, dense, texture-based flow visualization techniques are discussed. This class of techniques attempts to provide a complete, dense representation of the flow field with high spatio-temporal coherency. An attempt of categorizing closely related solutions is incorporated and presented. Fundamentals are shortly addressed as well as advantages and disadvantages of the methods.
Compression of Large-Scale Terrain Data for Real-Time Visualization Using a Tiled Quad Tree
(The Eurographics Association and Blackwell Publishing Ltd., 2004) Platings, M.; Day, A. M.
The aim of the rapid world modeling project is to implement a system to visualize the topography of the entire world on consumer-level hardware. This presents a significant problem in terms of both storage requirements and rendering speed. This paper presents the a??Tiled Quad Treea??, a technique and format for the storage of digital terrain models, to work as part of an integrated system for the visualization of global terrain data. We show how this format efficiently stores and compresses elevation data, in a way that allows the data to be read very rapidly from hard disk or similar storage medium, to facilitate real-time rendering. The results of compressing several distinct data sets are presented.
Editorial
(2004)
Smooth Surface Reconstruction Using Tensor Fields as Structuring Elements
(The Eurographics Association and Blackwell Publishing Ltd., 2004) Vieira, M. B.; Martins, P. P.; Araujo, A. A.; Cord, M.; Philipp-Foliguet, S.
We propose a new strategy to estimate surface normal information from highly noisy sparse data. Our approach is based on a tensor field morphologically adapted to infer normals. It acts as a three-dimensional structuring element of smooth surfaces. Robust orientation inference for all input elements is performed by morphological operations using the tensor field. A general normal estimator is defined by combining the inferred normals, their confidences and the tensor field. This estimator can be used to directly reconstruct the surface or give input normals to other reconstruction methods. We present qualitative and quantitative results to show the behavior of the original methods and ours. A comparative discussion of these results shows the efficiency of our propositions.

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