EG2009

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https://diglib.eg.org/handle/10.2312/269

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Wind projection basis for real-time animation of trees
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Diener, Julien; Rodriguez, Mathieu; Baboud, Lionel; Reveret, Lionel
This paper presents a real-time method to animate complex scenes of thousands of trees under a user-controllable wind load. Firstly, modal analysis is applied to extract the main modes of deformation from the mechanical model of a 3D tree. The novelty of our contribution is to precompute a new basis of the modal stress of the tree under wind load. At runtime, this basis allows to replace the modal projection of the external forces by a direct mapping for any directional wind. We show that this approach can be efficiently implemented on graphics hardware. This modal animation can be simulated at low computation cost even for large scenes containing thousands of trees.
Interactive Modeling of Virtual Ecosystems
(The Eurographics Association, 2009) Benes, Bedrich; Andrysco, Nathan; Stava, Ondrej; Eric Galin and Jens Schneider
We present a novel technique for interactive, intuitive, and efficient modeling of virtual plants and plant ecosystems. Our approach is biologically-based, but shades the user from overwhelming input parameters by simplifying them to intuitive controls. Users are able to create scenes that are populated by virtual plants. Plants communicate actively with the environment and attempt to generate an optimal spatial distribution that dynamically adapts to neighboring plants, to user defined obstacles, light, and gravity. We demonstrate simulations of ecosystems composed of up to 140 trees that are computed in less than two minutes. Various phenomena previously available for non-realtime procedural approaches are created interactively, such as plants competing for space, topiary, plant lighting, virtual forests, etc. Results are aimed at architectural modeling, the entertainment industry, and everywhere that quick and fast creation of believable biological plant models is necessary.
A Dynamic Caching System for Rendering an Animated Crowd in Real-Time
(The Eurographics Association, 2009) Lister, Wayne; Laycock, Robert G.; Day, Andrew M.; P. Alliez and M. Magnor
We present a method to accelerate the rendering of large crowds of animated characters. Recent trends have seen matrix-palette skinning become the prevalent approach due to its low memory overhead and fully dynamic geometry. However, the performance of skeletal animation remains modest in comparison to static rendering since neither temporal nor intra-frame coherency can be exploited. We cast crowd rendering as a memory-management problem and allocate a small geometry cache on the GPU within which animated characters can be stored. This serves to augment matrix-palette skinning with baked geometry and allows animation frames to be re-used by multi-pass rendering, between multiple agents and across multiple frames. Our method builds its cache dynamically and adapts to the current simulation state through use of the page-replacement algorithms traditionally employed by virtual-memory systems. In many cases this negates the need for skinning altogether and enables thousands of characters to be rendered in real-time, each independently animated and without loss of fidelity.
Energy Aware Color Sets
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Chuang, Johnson; Weiskopf, Daniel; Moeller, Torsten
We present a design technique for colors with the purpose of lowering the energy consumption of the display device. Our approach is based on a screen space variant energy model. The result of our design is a set of distinguishable iso-lightness colors guided by perceptual principles. We present two variations of our approach. One is based on a set of discrete user-named (categorical) colors, which are analyzed according to their energy consumption. The second is based on the constrained continuous optimization of color energy in the perceptually uniform CIELAB color space. We quantitatively compare our two approaches with a traditional choice of colors, demonstrating that we typically save approximately 40 percent of the energy. The color sets are applied to examples from the 2D visualization of nominal data and volume rendering of 3D scalar fields.
A Real-time Interactive Tool for Image Cutout
(The Eurographics Association, 2009) Liu, Chen; Li, Fengxia; Zhang, Yan; Zhan, Shouyi; P. Alliez and M. Magnor
We present an interactive tool for extracting foreground objects from image in real-time. As seen from the object boundary, the segmentation is to split pixel-pairs right on the boundary. The system utilizes the user input while the user roughly paints the stroke along the object boundary. Either side of the stroke is assumed to lie in foreground or background, and the mouse trace is supposed to coarsely indicate the object contour. We use the appearance, gradient and contour information to formulate the segmentation problem to an energy minimization problem, which is solved by graph cut. The appearance model is built via local sampling, since it often provides more discriminative model in local areas than that from global sampling. In addition, our system can dynamically adjust the stroke and the optimization region for which segmentation needs to be computed. The optimization region is much smaller than the whole image. This greatly reduces the computational complexity in each iteration and also gives the system the ability of incrementally segmenting. Experiments show the effectiveness of our methods in improving the segmentation performance.
Motion Compression using Principal Geodesics Analysis
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Tournier, M.; Wu, X.; Courty, N.; Arnaud, E.; Reveret, L.
Due to the growing need for large quantities of human animation data in the entertainment industry, it has become a necessity to compress motion capture sequences in order to ease their storage and transmission. We present a novel, lossy compression method for human motion data that exploits both temporal and spatial coherence. Given one motion, we first approximate the poses manifold using Principal Geodesics Analysis (PGA) in the configuration space of the skeleton. We then search this approximate manifold for poses matching end-effectors constraints using an iterative minimization algorithm that allows for real-time, data-driven inverse kinematics. The compression is achieved by only storing the approximate manifold parametrization along with the end-effectors and root joint trajectories, also compressed, in the output data. We recover poses using the IK algorithm given the end-effectors trajectories. Our experimental results show that considerable compression rates can be obtained using our method, with few reconstruction and perceptual errors.
Continuous Search and Replace in Vector Graphics
(The Eurographics Association, 2009) Loviscach, Joern; P. Alliez and M. Magnor
Many types of vector graphics comprise large numbers of almost identical partial shapes such as serifs in typeface design, ornaments in illustrations, and stylistic elements in icon design. As of today, later design changes of such shapes require the user to edit every instance on its own. Standard features of vector graphics software help with the automated replacement of stand-alone graphical objects, but do not cover partial shapes. Hence, a geometric search & replace function is needed, which is exacerbated by the circumstance that the repeated shapes construction from curve segments tends to vary from instance to instance, which requires a continuous approach that does not rely on a fixed division of a path into segments. This paper presents a geometric search and replace function that addresses these issues, possesses adjustable tolerance against orientation and size changes between the search pattern shape and the retrieved shapes, and is integrated with a standard vector graphics program.
Example-Based Rendering of Eye Movements
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Banf, Michael and Blanz, Volker
This paper describes a model for example-based, photo-realistic rendering of eye movements in 3D facial animation. Based on 3D scans of a face with different gaze directions, the model captures the motion of the eyeball along with the deformation of the eyelids and the surrounding skin. These deformations are represented in a 3D morphable model.Unlike the standard procedure in facial animation, the eyeball is not modeled as a rotating 3D sphere located behind the skin surface. Instead, the visible region of the eyeball is part of a continuous face mesh, and displacements of the iris as well as occlusions by the lids are modeled in a texture mapping approach. The algorithm avoids artifacts that are widely encountered in 3D facial animation, and it presents a new concept of handling occlusions and discontinuities in morphing algorithms.
Preface and Table of Contents
(The Eurographics Association, 2009) Bühler, K.; Bartz, D.; K. Bühler and D. Bartz
Preface and Table of Contents
Real Time Animation of Virtual Humans: A Trade-off Between Naturalness and Control
(The Eurographics Association, 2009) Welbergen, H. van; Basten, B. J. H. van; Egges, A.; Ruttkay, Zs.; Overmars, M. H.; M. Pauly and G. Greiner
Virtual humans are employed in many interactive applications using 3D virtual environments, including (serious) games. The motion of such virtual humans should look realistic (or natural ) and allow interaction with the surroundings and other (virtual) humans. Current animation techniques differ in the trade-off they offer between their motion naturalness and the amount of control that can be exerted over the motion. We give an overview of these techniques, focusing on the exact trade-offs made. We show how to parameterize, combine (on different body parts) and concatenate motions to gain control. We discuss several aspects of motion naturalness and show how it can be evaluated. We conclude by showing the promise of combinations of different animation paradigms to enhance both naturalness and control.
Frontmatter
(The Eurographics Association and Blackwell Publishing Ltd, 2009)
Temporal Glare: Real-Time Dynamic Simulation of the Scattering in the Human Eye
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Ritschel, T.; Ihrke, M.; Frisvad, J. R.; Coppens, J.; Myszkowski, K.; Seidel, H.-P.
Glare is a consequence of light scattered within the human eye when looking at bright light sources. This effect can be exploited for tone mapping since adding glare to the depiction of high-dynamic range (HDR) imagery on a low-dynamic range (LDR) medium can dramatically increase perceived contrast. Even though most, if not all, subjects report perceiving glare as a bright pattern that fluctuates in time, up to now it has only been modeled as a static phenomenon. We argue that the temporal properties of glare are a strong means to increase perceived brightness and to produce realistic and attractive renderings of bright light sources. Based on the anatomy of the human eye, we propose a model that enables real-time simulation of dynamic glare on a GPU. This allows an improved depiction of HDR images on LDR media for interactive applications like games, feature films, or even by adding movement to initially static HDR images. By conducting psychophysical studies, we validate that our method improves perceived brightness and that dynamic glare-renderings are often perceived as more attractive depending on the chosen scene.
Positional, Metric, and Curvature Control for Constraint-Based Surface Deformation
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Eigensatz, Michael; Pauly, Mark
We present a geometry processing framework that allows direct manipulation or preservation of positional, metric, and curvature constraints anywhere on the surface of a geometric model. Target values for these properties can be specified point-wise or as integrated quantities over curves and surface patches embedded in the shape. For example, the user can draw several curves on the surface and specify desired target lengths, manipulate the normal curvature along these curves, or modify the area or principal curvature distribution of arbitrary surface patches. This user input is converted into a set of non-linear constraints. A global optimization finds the new deformed surface that best satisfies the constraints, while minimizing adaptable measures for metric and curvature distortion that provide explicit control of the deformation semantics. We illustrate how this approach enables flexible surface processing and shape editing operations not available in current systems.
Heightfield and spatially varying BRDF Reconstruction for Materials with Interreflections
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Ruiters, Roland; Klein, Reinhard
Photo-realistic reproduction of material appearance from images has widespread use in applications ranging from movies over advertising to virtual prototyping. A common approach to this task is to reconstruct the small scale geometry of the sample and to capture the reflectance properties using spatially varying BRDFs. For this, multi-view and photometric stereo reconstruction can be used, both of which are limited regarding the amount of either view or light directions and suffer from either low- or high-frequency artifacts, respectively. In this paper, we propose a new algorithm combining both techniques to recover heightfields and spatially varying BRDFs while at the same time overcoming the above mentioned drawbacks. Our main contribution is a novel objective function which allows for the reconstruction of a heightfield and high quality SVBRDF including view dependent effects. Thereby, our method also avoids both low and high frequency artifacts. Additionally, our algorithm takes inter-reflections into account allowing for the reconstruction of undisturbed representations of the underlying material. In our experiments, including synthetic and real-world data, we show that our approach is superior to state-of-the-art methods regarding reconstruction error as well as visual impression. Both the reconstructed geometry and the recovered SVBRDF are highly accurate, resulting in a faithful reproduction of the materials characteristic appearance, which is of paramount importance in the context of material rendering.
Range Scan Registration Using Reduced Deformable Models
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Chang, W.; Zwicker, M.
We present an unsupervised method for registering range scans of deforming, articulated shapes. The key idea is to model the motion of the underlying object using a reduced deformable model. We use a linear skinning model for its simplicity and represent the weight functions on a regular grid localized to the surface geometry. This decouples the deformation model from the surface representation and allows us to deal with the severe occlusion and missing data that is inherent in range scan data. We formulate the registration problem using an objective function that enforces close alignment of the 3D data and includes an intuitive notion of joints. This leads to an optimization problem that we solve using an efficient EM-type algorithm. With our algorithm we obtain smooth deformations that accurately register pairs of range scans with significant motion and occlusion. The main advantages of our approach are that it does not require user specified markers, a template, nor manual segmentation of the surface geometry into rigid parts.
Continuum-based Strain Limiting
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Thomaszewski, Bernhard; Pabst, Simon; Strasser, Wolfgang
We present Continuum-based Strain Limiting (CSL) - a new method for limiting deformations in physically-based cloth simulations. Despite recent developments for nearly inextensible materials, the efficient simulation of general biphasic textiles and their anisotropic behavior remains challenging. Many approaches use soft materials and enforce limits on edge elongations, leading to discretization-dependent behavior. Moreover, they offer no explicit control over shearing and stretching unless specifically aligned meshes are used. Based on a continuum deformation measure, our method allows accurate control over all strain components using individual thresholds. We impose deformation limits element-wise and cast the problem as a 6x6 system of linear equations. CSL can be combined with any cloth simulator and, as a velocity filter, integrates seamlessly into standard collision handling.
Character Motion Synthesis by Topology Coordinates
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Ho, Edmond S.L.; Komura, Taku
In this paper, we propose a new method to efficiently synthesize character motions that involve close contacts such as wearing a T-shirt, passing the arms through the strings of a knapsack, or piggy-back carrying an injured person. We introduce the concept of topology coordinates, in which the topological relationships of the segments are embedded into the attributes. As a result, the computation for collision avoidance can be greatly reduced for complex motions that require tangling the segments of the body. Our method can be combinedly used with other prevalent frame-based optimization techniques such as inverse kinematics.
Course: Modeling Individualities in Groups and Crowds
(The Eurographics Association, 2009) Donikian, Stéphane; Magnenat-Thalmann, Nadia; Pettré, Julien; Thalmann, Daniel; K. Museth and D. Weiskopf
Crowds are part of our everyday life experience and essential when working with realistic interactive environments. Domains of application for such simulations range from populating artificial cities to entertainment, and virtual reality exposure therapy for crowd phobia. We mainly focus on real-time applications where the visual uniqueness of the characters composing a crowd is paramount. On the one hand, it is required to display several thousands of virtual humans at high frame rates. On the other hand, each character has to be different from all others, and its visual quality highly detailed. Variety in rendering is defined as having different forms or types and is necessary to create believable and reliable crowds in opposition to uniform crowds. For a human crowd, variation can come from the following aspects: gender, age, morphology, head, kind of clothes, color of clothes and behaviors.
Dent Removal: Geodesic Curve-Based Mesh Fairing
(The Eurographics Association, 2009) Pinskiy, Dmitriy; P. Alliez and M. Magnor
This paper presents a novel mesh fairing method to remove unwanted geometric artifacts such as dents. The key element of the proposed method is our unique algorithm for the assignment of weights in the discrete Laplacian. Our weights reflect the orientation of the first ring of vertices around a given vertex with respect to the whole dented region, rather than the ring's local geometry (e.g. Gauss or mean curvature flow that needs to be reestimated per each iteration). To establish the dent region s global behavior, we perform principal curvature analysis to determine representative geodesic curves for the surface. Our method is efficient as it only needs to compute the geodesic curves once, and then it uses them to guide subsequent iterations of anisotropic relaxation.
Over Two Decades of Integration-Based, Geometric Flow Visualization
(The Eurographics Association, 2009) McLoughlin, Tony; Laramee, Robert S.; Peikert, Ronald; Post, Frits H.; Chen, Min; M. Pauly and G. Greiner
Flow visualization is a fascinating sub-branch of scientific visualization. With ever increasing computing power, it is possible to process ever more complex fluid simulations. However, a gap between data set sizes and our ability to visualize them remains. This is especially true for the field of flow visualization which deals with large, timedependent, multivariate simulation datasets. In this paper, geometry based flow visualization techniques form the focus of discussion. Geometric flow visualization methods place discrete objects in the vector field whose characteristics reflect the underlying properties of the flow. A great amount of progress has been made in this field over the last two decades. However, a number of challenges remain, including placement, speed of computation, and perception. In this survey, we review and classify geometric flow visualization literature according to the most important challenges when considering such a visualization, a central theme being the seeding object upon which they are based. This paper details our investigation into these techniques with discussions on their applicability and their relative merits and drawbacks. The result is an up-to-date overview of the current state-of-the-art that highlights both solved and unsolved problems in this rapidly evolving branch of research. It also serves as a concise introduction to the field of flow visualization research.

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