31-Issue 7

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https://diglib.eg.org/handle/10.2312/176

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Video Panorama for 2D to 3D Conversion
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Ribera, Roger Blanco i; Choi, Sungwoo; Kim, Younghui; Lee, JungJin; Noh, Junyong; C. Bregler, P. Sander, and M. Wimmer
Accurate depth estimation is a challenging, yet essential step in the conversion of a 2D image sequence to a 3D stereo sequence. We present a novel approach to construct a temporally coherent depth map for each image in a sequence. The quality of the estimated depth is high enough for the purpose of 2D to 3D stereo conversion. Our approach first combines the video sequence into a panoramic image. A user can scribble on this single panoramic image to specify depth information. The depth is then propagated to the remainder of the panoramic image. This depth map is then remapped to the original sequence and used as the initial guess for each individual depth map in the sequence. Our approach greatly simplifies the required user interaction during the assignment of the depth and allows for relatively free camera movement during the generation of a panoramic image. We demonstrate the effectiveness of our method by showing stereo converted sequences with various camera motions.
Hierarchical Narrative Collage For Digital Photo Album
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Zhang, Lei; Huang, Hua; C. Bregler, P. Sander, and M. Wimmer
Collage can provide a summary form on the collection of photos in an album. In this paper, we introduce a novel approach to constructing photo collage in the hierarchical narrative manner. As opposed to previous methods focusing on spatial coherence in the collage layout, our narrative collage arranges the photos according to the basic narrative elements from literary writings, i.e., character, setting and plot. Face, time and place attributes are exploited to embody those narrative elements in the collage. Then, photos are organized into the hierarchical structure for the multi-level details in the events recorded by the album. Such hierarchical narrative collage can present a visual overview in the chronological order on what happened in the album. Experimental results show that our approach offers a better summarization to browse on the photo album content than previous ones.
Preface and Table of Contents
(The Eurographics Association and Blackwell Publishing Ltd., 2012) C. Bregler, P. Sander, and M. Wimmer
Scalable Programmable Motion Effects on GPUs
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Huang, Xuezhen; Hou, Qiming; Ren, Zhong; Zhou, Kun; C. Bregler, P. Sander, and M. Wimmer
We present an efficient and scalable system that enables programmable motion effects on GPUs. Our system is based on the framework proposed by Schmid et al. [SSBG10] that extends the concept of a surface shader to that of a programmable motion effect. While capable of expressing a variety of motion depiction styles, the execution of motion effect programs requires global knowledge about all portions of an object's surface that passes in front of a pixel during an arbitrarily long period of time, resulting in extremely high memory usage and significantly restricting the degree of parallelism of typical GPU rendering algorithms that parallelize computations over pixels in each frame of animations. To address this problem, we design our system to process multiple frames of a pixel in parallel. This new parallelization approach enables better utilization of GPU memory and also makes it possible to design an efficient out-of-core algorithm required in rendering real-world animations. We also develop an analytical visibility algorithm to resolve depth conflicts of objects, reducing the required temporal resampling rate and further exposing parallelism. Experiments show that we are able to handle very large scenes and improve runtime performance up to an order of magnitude.
Accurate Translucent Material Rendering under Spherical Gaussian Lights
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Yan, Ling-Qi; Zhou, Yahan; Xu, Kun; Wang, Rui; C. Bregler, P. Sander, and M. Wimmer
In this paper we present a new algorithm for accurate rendering of translucent materials under Spherical Gaussian (SG) lights. Our algorithm builds upon the quantized-diffusion BSSRDF model recently introduced in [dI11]. Our main contribution is an efficient algorithm for computing the integral of the BSSRDF with an SG light. We incorporate both single and multiple scattering components. Our model improves upon previous work by accounting for the incident angle of each individual SG light. This leads to more accurate rendering results, notably elliptical profiles from oblique illumination. In contrast, most existing models only consider the total irradiance received from all lights, hence can only generate circular profiles. Experimental results show that our method is suitable for rendering of translucent materials under finite-area lights or environment lights that can be approximated by a small number of SGs.
A Global Parity Measure for Incomplete Point Cloud Data
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Seversky, Lee M.; Yin, Lijun; C. Bregler, P. Sander, and M. Wimmer
Shapes with complex geometric and topological features such as tunnels, neighboring sheets, and cavities are susceptible to undersampling and continue to challenge existing reconstruction techniques. In this work we introduce a new measure for point clouds to determine the likely interior and exterior regions of an object. Specifically, we adapt the concept of parity to point clouds with missing data and introduce the parity map, a global measure of parity over the volume. We first examine how parity changes over the volume with respect to missing data and develop a method for extracting topologically correct interior and exterior crusts for estimating a signed distance field and performing surface reconstruction. We evaluate our approach on real scan data representing complex shapes with missing data. Our parity measure is not only able to identify highly confident interior and exterior regions but also localizes regions of missing data. Our reconstruction results are compared to existing methods and we show that our method faithfully captures the topology and geometry of complex shapes in the presence of missing data.
Retrieval and Visualization of Human Motion Data via Stick Figures
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Choi, Myung Geol; Yang, Kyungyong; Igarashi, Takeo; Mitani, Jun; Lee, Jehee; C. Bregler, P. Sander, and M. Wimmer
We propose 2D stick figures as a unified medium for visualizing and searching for human motion data. The stick figures can express a wide range or human motion, and they are easy to be drawn by people without any professional training. In our interface, the user can browse overall motion by viewing the stick figure images generated from the database and retrieve them directly by using sketched stick figures as an input query. We started with a preliminary survey to observe how people draw stick figures. Based on the rules observed from the user study, we developed an algorithm converting motion data to a sequence of stick figures. The feature-based comparison method between the stick figures provides an interactive and progressive search for the users. They assist the user's sketching by showing the current retrieval result at each stroke. We demonstrate the utility of the system with a user study, in which the participants retrieved example motion segments from the database with 102 motion files by using our interface.
Improving Photo Composition Elegantly: Considering Image Similarity During Composition
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Guo, Yanwen; Liu, Ming; Gu, Tingting; Wang, Wenping; C. Bregler, P. Sander, and M. Wimmer
Optimization of images with bad compositions has attracted increasing attention in recent years. Previous methods however seldomly consider image similarity when improving composition aesthetics. This may lead to significant content changes or bring large distortions, resulting in an unpleasant user experience. In this paper, we present a new algorithm for improving image composition aesthetics, while retaining faithful, as much as possible, to the original image content. Our method computes an improved image using a unified model of composition aesthetics and image similarity. The term of composition aesthetics obeys the rule of thirds and aims to enhance image composition. The similarity term in contrast penalizes image difference and distortion caused by composition adjustment. We use an edge-based measure of structure similarity which nearly coincides with human visual perception to compare the optimized image with the original one. We describe an effective scheme to generate the optimized image with the objective model. Our algorithm is able to produce the recomposed images with minimal visual distortions in an elegant and user controllable manner. We show the superiority of our algorithm by comparing our results with those by previous methods.
Homunculus Warping: Conveying Importance Using Self-intersection-free Non-homogeneous Mesh Deformation
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Reinert, Bernhard; Ritschel, Tobias; Seidel, Hans-Peter; C. Bregler, P. Sander, and M. Wimmer
Size matters. Human perception most naturally relates relative extent, area or volume to importance, nearness and weight. Reversely, conveying importance of something by depicting it at a different size is a classic artistic principle, in particular when importance varies across a domain. One striking example is the neuronal homunculus; a human figure where the size of each body part is proportional to the neural density on that part. In this work we propose an approach which changes local size of a 2D image or 3D surface and, at the same time, minimizes distortion, prevails smoothness, and, most importantly, avoids fold-overs (collisions). We employ a parallel, two-stage optimization process, that scales the shape non-uniformly according to an interactively-defined importance map and then solves for a nearby, self-intersection-free configuration. The results include an interactive 3D-rendered version of the classic sensorical homunculus but also a range of images and surfaces with different importance maps.
Adaptive Cross-sections of Anatomical Models
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Díaz, Jose; Monclús, Eva; Navazo, Isabel; Vázquez, Pere-Pau; C. Bregler, P. Sander, and M. Wimmer
Medical illustrations have been used for a long time for teaching and communicating information for diagnosis or surgery planning. Illustrative visualization systems create methods and tools that adapt traditional illustration techniques to enhance the result of renderings. Clipping the volume is a popular operation in volume rendering for inspecting the inner parts, though it may remove some information of the context that is worth preserving. In this paper we present a new editing technique based on the use of clipping planes, direct structure extrusion, and illustrative methods, which preserves the context by adapting the extruded region to the structures of interest of the volumetric model. We will show that users may interactively modify the clipping plane and edit the structures to highlight, in order to easily create the desired result. Our approach works with segmented volume models and nonsegmented ones. In the last case, a local segmentation is performed on-the-fly. We will demonstrate the efficiency and utility of our method.
Two-Finger Gestures for 6DOF Manipulation of 3D Objects
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Liu, Jingbo; Au, Oscar Kin-Chung; Fu, Hongbo; Tai, Chiew-Lan; C. Bregler, P. Sander, and M. Wimmer
Multitouch input devices afford effective solutions for 6DOF (six Degrees of Freedom) manipulation of 3D objects. Mainly focusing on large-size multitouch screens, existing solutions typically require at least three fingers and bimanual interaction for full 6DOF manipulation. However, single-hand, two-finger operations are preferred especially for portable multitouch devices (e.g., popular smartphones) to cause less hand occlusion and relieve the other hand for necessary tasks like holding the devices. Our key idea for full 6DOF control using only two contact fingers is to introduce two manipulation modes and two corresponding gestures by examining the moving characteristics of the two fingers, instead of the number of fingers or the directness of individual fingers as done in previous works. We solve the resulting binary classification problem using a learning-based approach. Our pilot experiment shows that with only two contact fingers and typically unimanual interaction, our technique is comparable to or even better than the state-of-the-art techniques.
SD Models: Super-Deformed Character Models
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Shen, Liang-Tsen; Luo, Sheng-Jie; Huang, Chun-Kai; Chen, Bing-Yu; C. Bregler, P. Sander, and M. Wimmer
Super-deformed, SD, is a specific artistic style for Japanese manga and anime which exaggerates characters in the goal of appearing cute and funny. The SD style characters are widely used, and can be seen in many anime, CG movies, or games. However, to create an SD model often requires professional skills and considerable time and effort. In this paper, we present a novel technique to generate an SD style counterpart of a normal 3D character model. Our approach uses an optimization guided by a number of constraints that can capture the properties of the SD style. Users can also customize the results by specifying a small set of parameters related to the body proportions and the emphasis of the signature characteristics. With our technique, even a novel user can generate visually pleasing SD models in seconds.
Wetting Effects in Hair Simulation
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Rungjiratananon, Witawat; Kanamori, Yoshihiro; Nishita, Tomoyuki; C. Bregler, P. Sander, and M. Wimmer
There is considerable recent progress in hair simulations, driven by the high demands in computer animated movies. However, capturing the complex interactions between hair and water is still relatively in its infancy. Such interactions are best modeled as those between water and an anisotropic permeable medium as water can flow into and out of the hair volume biased in hair fiber direction. Modeling the interaction is further challenged when the hair is allowed to move. In this paper, we introduce a simulation model that reproduces interactions between water and hair as a dynamic anisotropic permeable material. We utilize an Eulerian approach for capturing the microscopic porosity of hair and handle the wetting effects using a Cartesian bounding grid. A Lagrangian approach is used to simulate every single hair strand including interactions with each other, yielding fine-detailed dynamic hair simulation. Our model and simulation generate many interesting effects of interactions between fine-detailed dynamic hair and water, i.e., water absorption and diffusion, cohesion of wet hair strands, water flow within the hair volume, water dripping from the wet hair strands and morphological shape transformations of wet hair.
Realtime Two-Way Coupling of Meshless Fluids and Nonlinear FEM
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Yang, Lipeng; Li, Shuai; Hao, Aimin; Qin, Hong; C. Bregler, P. Sander, and M. Wimmer
In this paper, we present a novel method to couple Smoothed Particle Hydrodynamics (SPH) and nonlinear FEM to animate the interaction of fluids and deformable solids in real time. To accurately model the coupling, we generate proxy particles over the boundary of deformable solids to facilitate the interaction with fluid particles, and develop an efficient method to distribute the coupling forces of proxy particles to FEM nodal points. Specifically, we employ the Total Lagrangian Explicit Dynamics (TLED) finite element algorithm for nonlinear FEM because of many of its attractive properties such as supporting massive parallelism, avoiding dynamic update of stiffness matrix computation, and efficient solver. Based on a predictor-corrector scheme for both velocity and position, different normal and tangential conditions can be realized even for shell-like thin solids. Our coupling method is entirely implemented on modern GPUs using CUDA. We demonstrate the advantage of our two-way coupling method in computer animation via various virtual scenarios.
Semi-supervised Mesh Segmentation and Labeling
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Lv, Jiajun; Chen, Xinlei; Huang, Jin; Bao, Hujun; C. Bregler, P. Sander, and M. Wimmer
Recently, approaches have been put forward that focus on the recognition of mesh semantic meanings. These methods usually need prior knowledge learned from training dataset, but when the size of the training dataset is small, or the meshes are too complex, the segmentation performance will be greatly effected. This paper introduces an approach to the semantic mesh segmentation and labeling which incorporates knowledge imparted by both segmented, labeled meshes, and unsegmented, unlabeled meshes. A Conditional Random Fields (CRF) based objective function measuring the consistency of labels and faces, labels of neighbouring faces is proposed. To implant the information from the unlabeled meshes, we add an unlabeled conditional entropy into the objective function. With the entropy, the objective function is not convex and hard to optimize, so we modify the Virtual Evidence Boosting (VEB) to solve the semi-supervised problem efficiently. Our approach yields better results than those methods which only use limited labeled meshes, especially when many unlabeled meshes exist. The approach reduces the overall system cost as well as the human labelling cost required during training. We also show that combining knowledge from labeled and unlabeled meshes outperforms using either type of meshes alone.
Performance Capture of High-Speed Motion Using Staggered Multi-View Recording
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Wu, Di; Liu, Yebin; Ihrke, Ivo; Dai, Qionghai; Theobalt, Christian; C. Bregler, P. Sander, and M. Wimmer
We present a markerless performance capture system that can acquire the motion and the texture of human actors performing fast movements using only commodity hardware. To this end we introduce two novel concepts: First, a staggered surround multi-view recording setup that enables us to perform model-based motion capture on motion-blurred images, and second, a model-based deblurring algorithm which is able to handle disocclusion, self-occlusion and complex object motions. We show that the model-based approach is not only a powerful strategy for tracking but also for deblurring highly complex blur patterns.
Registration Based Non-uniform Motion Deblurring
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Cho, Sunghyun; Cho, Hojin; Tai, Yu-Wing; Lee, Seungyong; C. Bregler, P. Sander, and M. Wimmer
This paper proposes an algorithm which uses image registration to estimate a non-uniform motion blur point spread function (PSF) caused by camera shake. Our study is based on a motion blur model which models blur effects of camera shakes using a set of planar perspective projections (i.e., homographies). This representation can fully describe motions of camera shakes in 3D which cause non-uniform motion blurs. We transform the non-uniform PSF estimation problem into a set of image registration problems which estimate homographies of the motion blur model one-by-one through the Lucas-Kanade algorithm. We demonstrate the performance of our algorithm using both synthetic and real world examples. We also discuss the effectiveness and limitations of our algorithm for non-uniform deblurring.
Wake Synthesis For Shallow Water Equation
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Pan, Zherong; Huang, Jin; Tong, Yiying; Bao, Hujun; C. Bregler, P. Sander, and M. Wimmer
In fluid animation, wake is one of the most important phenomena usually seen when an object is moving relative to the flow. However, in current shallow water simulation for interactive applications, this effect is greatly smeared out. In this paper, we present a method to efficiently synthesize these wakes. We adopt a generalized SPH method for shallow water simulation and two way solid fluid coupling. In addition, a 2D discrete vortex method is used to capture the detailed wake motions behind an obstacle, enriching the motion of SWE simulation. Our method is highly efficient since only 2D simulation is required. Moreover, by using a physically inspired procedural approach for particle seeding, DVM particles are only created in the wake region. Therefore, very few particles are required while still generating realistic wake patterns. When coupled with SWE, we show that these patterns can be seen using our method with marginal overhead.
Analytic Curve Skeletons for 3D Surface Modeling and Processing
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Thiery, Jean-Marc; Buchholz, Bert; Tierny, Julien; Boubekeur, Tamy; C. Bregler, P. Sander, and M. Wimmer
We present a new curve skeleton model designed for surface modeling and processing. This skeleton is defined as the geometrical integration of a piecewise harmonic parameterization defined over a disk-cylinder surface decomposition. This decomposition is computed using a progressive Region Graph reduction based on both geometric and topological criteria which can be iteratively optimized to improve region boundaries. The skeleton has an analytical form with regularity inherited from the surface one. Such a form offers well-defined surface-skeleton and skeleton-surface projections. The resulting skeleton satisfies quality criteria which are relevant for skeleton-based modeling and processing. We propose applications that benefit from our skeleton model, including local thickness editing, inset surface creation for shell mapping, as well as a new mid-scale feature preserving smoothing.
GPU Shape Grammars
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Marvie, Jean-Eudes; Buron, Cyprien; Gautron, Pascal; Hirtzlin, Patrice; Sourimant, Gaël; C. Bregler, P. Sander, and M. Wimmer
GPU Shape Grammars provide a solution for interactive procedural generation, tuning and visualization of massive environment elements for both video games and production rendering. Our technique generates detailed models without explicit geometry storage. To this end we reformulate the grammar expansion for generation of detailed models at the tesselation control and geometry shader stages. Using the geometry generation capabilities of modern graphics hardware, our technique generated massive, highly detailed models. GPU Shape Grammars integrate within a scalable framework by introducing automatic generation of levels of detail at reduced cost. We apply our solution for interactive generation and rendering of scenes containing thousands of buildings and trees.

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