Volume 28 (2009)

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https://diglib.eg.org/handle/10.2312/142

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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.
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.
Scalable, Versatile and Simple Constrained Graph Layout
(The Eurographics Association and Blackwell Publishing Ltd., 2009) Dwyer, Tim; H.-C. Hege, I. Hotz, and T. Munzner
We describe a new technique for graph layout subject to constraints. Compared to previous techniques the proposed method is much faster and scalable to much larger graphs. For a graph with n nodes, m edges and c constraints it computes incremental layout in time O(nlogn+m+c) per iteration. Also, it supports a much more powerful class of constraint: inequalities or equalities over the Euclidean distance between nodes.We demonstrate the power of this technique by application to a number of diagramming conventions which previous constrained graph layout methods could not support. Further, the constraint-satisfaction method inspired by recent work in position-based dynamics is far simpler to implement than previous methods.
Interactive Visualization of Function Fields by Range-Space Segmentation
(The Eurographics Association and Blackwell Publishing Ltd., 2009) Anderson, John C.; Gosink, Luke J.; Duchaineau, Mark A.; Joy, Ken I.; H.-C. Hege, I. Hotz, and T. Munzner
We present a dimension reduction and feature extraction method for the visualization and analysis of function field data. Function fields are a class of high-dimensional, multi-variate data in which data samples are onedimensional scalar functions. Our approach focuses upon the creation of high-dimensional range-space segmentations, from which we can generate meaningful visualizations and extract separating surfaces between features. We demonstrate our approach on high-dimensional spectral imagery, and particulate pollution data from air quality simulations.
Frontmatter
(The Eurographics Association and Blackwell Publishing Ltd, 2009)
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.
Texture Splicing
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Liu, Yiming; Wang, Jiaping; Xue, Su; Tong, Xin; Kang, Sing Bing; Guo, Baining
We propose a new texture editing operation called texture splicing. For this operation, we regard a texture as having repetitive elements (textons) seamlessly distributed in a particular pattern. Taking two textures as input, texture splicing generates a new texture by selecting the texton appearance from one texture and distribution from the other. Texture splicing involves self-similarity search to extract the distribution, distribution warping, context-dependent warping, and finally, texture refinement to preserve overall appearance. We show a variety of results to illustrate this operation.
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.
Interactive Graphics for Computer Adaptive Testing
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Cheng, I.; Basu, A.
Interactive graphics are commonly used in games and have been shown to be successful in attracting the general audience. Instead of computer games, animations, cartoons, and videos being used only for entertainment, there is now an interest in using interactive graphics for innovative testing . Rather than traditional pen-and-paper tests, audio, video and graphics are being conceived as alternative means for more effective testing in the future. In this paper, we review some examples of graphics item types for testing. As well, we outline how games can be used to interactively test concepts; discuss designing chemistry item types with interactive 3D graphics; suggest approaches for automatically adjusting difficulty level in interactive graphics based questions; and propose strategies for giving partial marks for incorrect answers. We study how to test different cognitive skills, such as music, using multimedia interfaces; and also evaluate the effectiveness of our model. Methods for estimating difficulty level of a mathematical item type using Item Response Theory (IRT) and a molecule construction item type using Graph Edit Distance are discussed. Evaluation of the graphics item types through extensive testing on some students is described. We also outline the application of using interactive graphics over cell phones. All of the graphics item types used in this paper are developed by members of our research group.
Frontmatter
(The Eurographics Association and Blackwell Publishing Ltd, 2009)
Expression Synthesis and Transfer in Parameter Spaces
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Shin, Hyun Joon; Lee, Yunjin
In this paper, we introduce a novel framework that allows users to synthesize the expression of a 3D character by providing a intuitive set of parametric controls. Assuming that human face movements are formed by a set of basis actuation, we analyze a set of real expressions to extract this set together with skin deformation due to the actuation of face. To do this, we first decompose the movement of each marker into a set of distinctive movements. Independent component analysis technique is then adopted to find a independent set of actuations. Our simple and efficient skin deformation model are learned to reproduce the realistic movements of facial parts due to the actuations. In this framework, users can animate characters faces by controlling the amount actuation or by directly manipulating the face geometry. In addition, the proposed method can be applied to expression transfer which reproduces one character s expression in another character s face. Experimental results demonstrate that our method can produce realistic expression efficiently.
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.
Editing Object Behaviour in Video Sequences
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Scholz, Volker; El-Abed, Sascha; Seidel, Hans-Peter; Magnor, Marcus
While there are various commercial-strength editing tools available today for still images, object-based manipulation of real-world video footage is still a challenging problem. In this system paper, we present a framework for interactive video editing. Our focus is on footage from a single, conventional video camera. By relying on spatio-temporal editing techniques operating on the video cube, we do not need to recover 3D scene geometry. Our framework is capable of removing and inserting objects, object motion editing, non-rigid object deformations, keyframe interpolation, as well as emulating camera motion. We demonstrate how movie shots with moderate complexity can be persuasively modified during post-processing.
Frontmatter
(The Eurographics Association and Blackwell Publishing Ltd, 2009)
Fast Isosurface Rendering on a GPU by Cell Rasterization
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Liu, B.; Clapworthy, G. J.; Dong, F.
This paper presents a fast, high-quality, GPU-based isosurface rendering pipeline for implicit surfaces defined by a regular volumetric grid. GPUs are designed primarily for use with polygonal primitives, rather than volume primitives, but here we directly treat each volume cell as a single rendering primitive by designing a vertex program and fragment program on a commodity GPU. Compared with previous raycasting methods, ours has a more effective memory footprint (cache locality) and better coherence between multiple parallel SIMD processors. Furthermore, we extend and speed up our approach by introducing a new view-dependent sorting algorithm to take advantage of the early-z-culling feature of the GPU to gain significant performance speed-up. As another advantage, this sorting algorithm makes multiple transparent isosurfaces rendering available almost for free. Finally, we demonstrate the effectiveness and quality of our techniques in several real-time rendering scenarios and include analysis and comparisons with previous work.
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.
Resolution Independent NPR-Style 3D Line Textures
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Potter, Kristin; Gooch, Amy; Gooch, Bruce; Willemsen, Peter; Kniss, Joe; Riesenfeld, Richard; Shirley, Peter
This work introduces a technique for interactive walk-throughs of non-photorealistically rendered (NPR) scenes using three-dimensional (3D) line primitives to define architectural features of the model, as well as indicate textural qualities. Line primitives are not typically used in this manner in favour of texture mapping techniques which can encapsulate a great deal of information in a single texture map, and take advantage of GPU optimizations for accelerated rendering. However, texture mapped images may not maintain the visual quality or aesthetic appeal that is possible when using 3D lines to simulate NPR scenes such as hand-drawn illustrations or architectural renderings. In addition, line textures can be modified interactively, for instance changing the sketchy quality of the lines. The technique introduced here extracts feature edges from a model, and using these edges, generates a reduced set of line textures which indicate material properties while maintaining interactive frame rates. A clipping algorithm is presented to enable 3D lines to reside only in the interior of the 3D model without exposing the underlying triangulated mesh. The resulting system produces interactive illustrations with high visual quality that are free from animation artifacts.
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.
Selecting Good Views of High-dimensional Data using Class Consistency
(The Eurographics Association and Blackwell Publishing Ltd., 2009) Sips, Mike; Neubert, Boris; Lewis, John P.; Hanrahan, Pat; H.-C. Hege, I. Hotz, and T. Munzner
Abstract Many visualization techniques involve mapping high-dimensional data spaces to lower-dimensional views. Unfortunately, mapping a high-dimensional data space into a scatterplot involves a loss of information; or, even worse, it can give a misleading picture of valuable structure in higher dimensions. In this paper, we propose class consistency as a measure of the quality of the mapping. Class consistency enforces the constraint that classes of n D data are shown clearly in 2 D scatterplots. We propose two quantitative measures of class consistency, one based on the distance to the class s center of gravity, and another based on the entropies of the spatial distributions of classes. We performed an experiment where users choose good views, and show that class consistency has good precision and recall. We also evaluate both consistency measures over a range of data sets and show that these measures are efficient and robust.

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