Volume 26 (2007)

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https://diglib.eg.org/handle/10.2312/128

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12th Eurographics Symposium on Virtual Environments
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Hubbold, Roger; Jorge, Joaquim; Lin, Ming
28th EUROGRAPHICS General Assembly
(The Eurographics Association and Blackwell Publishing Ltd, 2007)
2nd EG workshop on Natural Phenomena September 5th, 2007 Vienna (Austria)
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Chiba, Norishige; Galin, Eric
3D Lip-Synch Generation with Data-Faithful Machine Learning
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Kim, Ig-Jae; Ko, Hyeong-Seok
This paper proposes a new technique for generating three-dimensional speech animation. The proposed technique takes advantage of both data-driven and machine learning approaches. It seeks to utilize the most relevant part of the captured utterances for the synthesis of input phoneme sequences. If highly relevant data are missing or lacking, then it utilizes less relevant (but more abundant) data and relies more heavily on machine learning for the lip-synch generation. This hybrid approach produces results that are more faithful to real data than conventional machine learning approaches, while being better able to handle incompleteness or redundancy in the database than conventional data-driven approaches. Experimental results, obtained by applying the proposed technique to the utterance of various words and phrases, show that (1) the proposed technique generates lip-synchs of different qualities depending on the availability of the data, and (2) the new technique produces more realistic results than conventional machine learning approaches.
3D Video Billboard Clouds
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Waschbuesch, Michael; Wuermlin, Stephan; Gross, Markus
3D video billboard clouds reconstruct and represent a dynamic three-dimensional scene using displacement-mapped billboards. They consist of geometric proxy planes augmented with detailed displacement maps and combine the generality of geometry-based 3D video with the regularization properties of image-based 3D video. 3D video billboards are an image-based representation placed in the disparity space of the acquisition cameras and thus provide a regular sampling of the scene with a uniform error model. We propose a general geometry filtering framework which generates time-coherent models and removes reconstruction and quantization noise as well as calibration errors. This replaces the complex and time-consuming sub-pixel matching process in stereo reconstruction with a bilateral filter. Rendering is performed using a GPU-accelerated algorithm which generates consistent view-dependent geometry and textures for each individual frame. In addition, we present a semi-automatic approach for modeling dynamic three-dimensional scenes with a set of multiple 3D video billboards clouds.
Accelerating Refractive Rendering of Transparent Objects
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Hui, K. C.; Lee, A. H. C.; Lai, Y. H.
In this paper, a technique is proposed for the rendering of transparent objects interactively using the method of refractive rendering. In the proposed technique, the refractive rendering algorithm is performed in two stages, namely the pre-computation stage and the shading stage. In the pre-computation stage, ray-traced information, including directions and positions of rays, are generated by a ray tracing process and are stored in a set of ray lists. In the shading stage, these data are retrieved from the ray lists for computing the shading of an object. Using the proposed technique, photorealistic image of transparent objects and gemstones with various cuttings, material properties, lighting and background can be rendered interactively. By combining the refractive rendering technique with conventional shading techniques, jewelry and crystal designs can be rendered at a much higher speed comparing with conventional ray tracing techniques.
Accurate Depth of Field Simulation in Real Time
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Zhou, Tianshu; Chen, Jim X.; Pullen, Mark
We present a new post processing method of simulating depth of field based on accurate calculations of circles of confusion. Compared to previous work, our method derives actual scene depth information directly from the existing depth buffer, requires no specialized rendering passes, and allows easy integration into existing rendering applications. Our implementation uses an adaptive, two-pass filter, producing a high quality depth of field effect that can be executed entirely on the GPU, taking advantage of the parallelism of modern graphics cards and permitting real time performance when applied to large numbers of pixels.
Adaptive Space Deformations Based on Rigid Cells
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Botsch, Mario; Pauly, Mark; Wicke, Martin; Gross, Markus
We propose a new adaptive space deformation method for interactive shape modeling. A novel energy formulation based on elastically coupled volumetric cells yields intuitive detail preservation even under large deformations. By enforcing rigidity of the cells, we obtain an extremely robust numerical solver for the resulting nonlinear optimization problem. Scalability is achieved using an adaptive spatial discretization that is decoupled from the resolution of the embedded object. Our approach is versatile and easy to implement, supports thin-shell and solid deformations of 2D and 3D objects, and is applicable to arbitrary sample-based representations, such as meshes, triangle soups, or point clouds.
Automatic Light Source Placement for Maximum Visual Information Recovery
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Vazquez, P.-P.
The automatic selection of good viewing parameters is a very complex problem. In most cases, the notion of good strongly depends on the concrete application. Moreover, when an intuitive definition of good view is available, it is often difficult to establish a measure that brings it to the practice. Commonly, two kinds of viewing parameters must be set: camera parameters (position and orientation) and lighting parameters (number of light sources, its position and eventually the orientation of the spot). The first parameters will determine how much of the geometry can be captured and the latter will influence on how much of it is revealed (i.e., illuminated) to the user. Unfortunately, ensuring that certain parts of a scene are lit does not make sure that the details will be communicated to the user, as the amount of illumination might be too small or too high. In this paper we define a metric to calculate the amount of information relative to an object that is effectively communicated to the user given a fixed camera position. This measure is based on an information-based concept, the Shannon entropy, and will be applied to the problem of automatic selection of light positions in order to adequately illuminate an object. In order to validate the results, we have carried out an experiment on users, this experiment helped us to explore other related measures.
A Bidirectional Light Field - Hologram Transform
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Ziegler, Remo; Bucheli, Simon; Ahrenberg, Lukas; Magnor, Marcus; Gross, Markus
In this paper, we propose a novel framework to represent visual information. Extending the notion of conventional image-based rendering, our framework makes joint use of both light fields and holograms as complementary representations. We demonstrate how light fields can be transformed into holograms, and vice versa. By exploiting the advantages of either representation, our proposed dual representation and processing pipeline is able to overcome the limitations inherent to light fields and holograms alone. We show various examples from synthetic and real light fields to digital holograms demonstrating advantages of either representation, such as speckle-free images, ghosting-free images, aliasing-free recording, natural light recording, aperture-dependent effects and real-time rendering which can all be achieved using the same framework. Capturing holograms under white light illumination is one promising application for future work.
Bitmask Soft Shadows
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Schwarz, Michael; Stamminger, Marc
Recently, several real-time soft shadow algorithms have been introduced which all compute a single shadow map and use its texels to obtain a discrete scene representation. The resulting micropatches are backprojected onto the light source and the light areas occluded by them get accumulated to estimate overall light occlusion. This approach ignores patch overlaps, however, which can lead to objectionable artifacts. In this paper, we propose to determine the visibility of the light source with a bit field where each bit tracks the visibility of a sample point on the light source. This approach not only avoids overlapping-related artifacts but offers a solution to the important occluder fusion problem. Hence, it also becomes possible to correctly incorporate information from multiple depth maps. In addition, a new interpretation of the shadow map data is suggested which often provides superior visual results. Finally, we show how the search area for potential occluders can be reduced substantially.
Boundary Constrained Swept Surfaces for Modelling and Animation
(The Eurographics Association and Blackwell Publishing Ltd, 2007) You, L. H.; Yang, X. S.; Pachulski, M.; Zhang, Jian J.
Due to their simplicity and intuitiveness, swept surfaces are widely used in many surface modelling applications. In this paper, we present a versatile swept surface technique called the boundary constrained swept surfaces. The most distinct feature is its ability to satisfy boundary constraints, including the shape and tangent conditions at the boundaries of a swept surface. This permits significantly varying surfaces to be both modelled and smoothly assembled, leading to the construction of complex objects. The representation, similar to an ordinary swept surface, is analytical in nature and thus it is light in storage cost and numerically very stable to compute. We also introduce a number of useful shape manipulation tools, such as sculpting forces, to deform a surface both locally and globally. In addition to being a complementary method to the mainstream surface modelling and deformation techniques, we have found it very effective in automatically rebuilding existing complex models. Model reconstruction is arguably one of the most laborious and expensive tasks in modelling complex animated characters. We demonstrate how our technique can be used to automate this process.
CGF Reviewers
(The Eurographics Association and Blackwell Publishing Ltd, 2007)
CGForum 2007 Cover Image Trillion Triangle Terrain by Andreas Dietrich, Gerd Marmitt and Philipp Slusallek
(The Eurographics Association and Blackwell Publishing Ltd, 2007)
Consistent Viewing and Interaction for Multiple Users in Projection-Based VR Systems
(The Eurographics Association and Blackwell Publishing Ltd, 2007) De Haan, Gerwin; Molenaar, Rene; Koutek, Michal; Post, Frits H.
In projection-based Virtual Reality (VR) systems, typically only one headtracked user views stereo images rendered from the correct view position. For other users, who are presented a distorted image, moving with the first user s head motion, it is difficult to correctly view and interact with 3D objects in the virtual environment. In close-range VR systems, such as the Virtual Workbench, distortion effects are especially large because objects are within close range and users are relatively far apart. On these systems, multi-user collaboration proves to be difficult. In this paper, we analyze the problem and describe a novel, easy to implement method to prevent and reduce image distortion and its negative effects on close-range interaction task performance. First, our method combines a shared camera model and view distortion compensation. It minimizes the overall distortion for each user, while important user-personal objects such as interaction cursors, rays and controls remain distortion-free. Second, our method retains co-location for interaction techniques to make interaction more consistent. We performed a user experiment on our Virtual Workbench to analyze user performance under distorted view conditions with and without the use of our method. Our findings demonstrate the negative impact of view distortion on task performance and the positive effect our method introduces. This indicates that our method can enhance the multi-user collaboration experience on close-range, projection-based VR systems.
Context-Aware Skeletal Shape Deformation
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Weber, Ofir; Sorkine, Olga; Lipman, Yaron; Gotsman, Craig
We describe a system for the animation of a skeleton-controlled articulated object that preserves the fine geometric details of the object skin and conforms to the characteristic shapes of the object specified through a set of examples. The system provides the animator with an intuitive user interface and produces compelling results even when presented with a very small set of examples. In addition it is able to generalize well by extrapolating far beyond the examples.
Contrast Restoration by Adaptive Countershading
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Krawczyk, Grzegorz; Myszkowski, Karol; Seidel, Hans-Peter
The ABSTRACT is to be in fully-justified italicized text, between two horizontal lines, in one-column format, below the author and affiliation information. Use the word Abstract as the title, in 9-point Times, boldface type, left-aligned to the text, initially capitalized. The abstract is to be in 9-point, single-spaced type. The abstract may be up to 3 inches (7.62 cm) long. Leave one blank line after the abstract, then add the subject categories according to the ACM Classification Index (see http://www.acm.org/class/1998/).
Crowds by Example
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Lerner, Alon; Chrysanthou, Yiorgos; Lischinski, Dani
We present an example-based crowd simulation technique. Most crowd simulation techniques assume that the behavior exhibited by each person in the crowd can be defined by a restricted set of rules. This assumption limits the behavioral complexity of the simulated agents. By learning from real-world examples, our autonomous agents display complex natural behaviors that are often missing in crowd simulations. Examples are created from tracked video segments of real pedestrian crowds. During a simulation, autonomous agents search for examples that closely match the situation that they are facing. Trajectories taken by real people in similar situations, are copied to the simulated agents, resulting in seemingly natural behaviors.
Data-driven Tetrahedral Mesh Subdivision
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Rodriguez, L.; Navazo, I.; Vinacua, A.
Given a tetrahedral mesh immersed in a voxel model, we present a method to refine the mesh to reduce the discrepancy between interpolated values based on either scheme at arbitrary locations. An advantage of the method presented is that it requires few subdivisions and all decisions are made locally at each tetrahedron. We discuss the algorithm s performance and applications.
Defocus Magnification
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Bae, Soonmin; Durand, Fredo
A blurry background due to shallow depth of field is often desired for photographs such as portraits, but, unfortunately, small point-and-shoot cameras do not permit enough defocus because of the small diameter of their lenses. We present an image-processing technique that increases the defocus in an image to simulate the shallow depth of field of a lens with a larger aperture.Our technique estimates the spatially-varying amount of blur over the image, and then uses a simple image-based technique to increase defocus. We first estimate the size of the blur kernel at edges and then propagate this defocus measure over the image. Using our defocus map, we magnify the existing blurriness, which means that we blur blurry regions and keep sharp regions sharp. In contrast to more difficult problems such as depth from defocus, we do not require precise depth estimation and do not need to disambiguate textureless regions.

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