31-Issue 7

Permanent URI for this collection

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

Browse

Now showing 1 - 20 of 31

Isotropic Surface Remeshing Using Constrained Centroidal Delaunay Mesh
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Chen, Zhonggui; Cao, Juan; Wang, Wenping; C. Bregler, P. Sander, and M. Wimmer
We develop a novel isotropic remeshing method based on constrained centroidal Delaunay mesh (CCDM), a generalization of centroidal patch triangulation from 2D to mesh surface. Our method starts with resampling an input mesh with a vertex distribution according to a user-defined density function. The initial remeshing result is then progressively optimized by alternatively recovering the Delaunay mesh and moving each vertex to the centroid of its 1-ring neighborhood. The key to making such simple iterations work is an efficient optimization framework that combines both local and global optimization methods. Our method is parameterization-free, thus avoiding the metric distortion introduced by parameterization, and generating more well-shaped triangles. Our method guarantees that the topology of surface is preserved without requiring geodesic information. We conduct various experiments to demonstrate the simplicity, efficacy, and robustness of the presented method.
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.
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.
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.
Preface and Table of Contents
(The Eurographics Association and Blackwell Publishing Ltd., 2012) C. Bregler, P. Sander, and M. Wimmer
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.
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.
Approximate Bias Compensation for Rendering Scenes with Heterogeneous Participating Media
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Engelhardt, Thomas; Novák, Jan; Schmidt, Thorsten-W.; Dachsbacher, Carsten; C. Bregler, P. Sander, and M. Wimmer
In this paper we present a novel method for high-quality rendering of scenes with participating media. Our technique is based on instant radiosity, which is used to approximate indirect illumination between surfaces by gathering light from a set of virtual point lights (VPLs). It has been shown that this principle can be applied to participating media as well, so that the combined single scattering contribution of VPLs within the medium yields full multiple scattering. As in the surface case, VPL methods for participating media are prone to singularities, which appear as bright ''splotches'' in the image. These artifacts are usually countered by clamping the VPLs' contribution, but this leads to energy loss within the short-distance light transport. Bias compensation recovers the missing energy, but previous approaches are prohibitively costly. We investigate VPL-based methods for rendering scenes with participating media, and propose a novel and efficient approximate bias compensation technique. We evaluate our technique using various test scenes, showing it to be visually indistinguishable from ground truth.
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.
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.
Texture Compression using Wavelet Decomposition
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Mavridis, Pavlos; Papaioannou, Georgios; C. Bregler, P. Sander, and M. Wimmer
In this paper we introduce a new fixed-rate texture compression scheme based on the energy compaction properties of a modified Haar transform. The coefficients of this transform are quantized and stored using standard block compression methods, such as DXTC and BC7, ensuring simple implementation and very fast decoding speeds. Furthermore, coefficients with the highest contribution to the final image are quantized with higher accuracy, improving the overall compression quality. The proposed modifications to the standard Haar transform, along with a number of additional optimizations, improve the coefficient quantization and reduce the compression error. The resulting method offers more flexibility than the currently available texture compression formats, providing a variety of additional low bitrate encoding modes for the compression of grayscale and color textures.
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.
Scale Normalization for Isometric Shape Matching
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Sahillioglu, Yusuf; Yemez, Yucel; C. Bregler, P. Sander, and M. Wimmer
We address the scale problem inherent to isometric shape correspondence in a combinatorial matching framework. We consider a particular setting of the general correspondence problem where one of the two shapes to be matched is an isometric (or nearly isometric) part of the other up to an arbitrary scale. We resolve the scale ambiguity by finding a coarse matching between shape extremities based on a novel scale-invariant isometric distortion measure. The proposed algorithm also supports (partial) dense matching, that alleviates the symmetric flip problem due to initial coarse sampling. We test the performance of our matching algorithm on several shape datasets in comparison to state of the art. Our method proves useful, not only for partial matching, but also for complete matching of semantically similar hybrid shape pairs whose maximum geodesic distances may not be compatible, a case that would fail most of the conventional isometric shape matchers.
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.
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.
Fur Shading and Modification based on Cone Step Mapping
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Kühnert, Tom; Brunnett, Guido; C. Bregler, P. Sander, and M. Wimmer
This paper presents an algorithm for the real time rendering of fur without adding fur-specific geometry, such as shells, to the object. It is based on Cone Step Mapping and introduces a local distortion of the view vector to simulate a deformation of the heightfield-bound hair geometry. While this distortion enables a more realistic fur rendering, some limitations emerge and have to be dealt with. A local light reflectance model including approximations of global light interactions with hair and skin is proposed. We furthermore show how material and geometric properties can locally be influenced through standard texture mapping. This includes most notably the local modification of growth and streak direction of the hairs.
Structure Preserving Manipulation and Interpolation for Multi-element 2D Shapes
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Yang, Wenwu; Feng, Jieqing; Wang, Xun; C. Bregler, P. Sander, and M. Wimmer
This paper presents a method that generates natural and intuitive deformations via direct manipulation and smooth interpolation for multi-element 2D shapes. Observing that the structural relationships between different parts of a multi-element 2D shape are important for capturing its feature semantics, we introduce a simple structure called a feature frame to represent such relationships. A constrained optimization is solved for shape manipulation to find optimal deformed shapes under user-specified handle constraints. Based on the feature frame, local feature preservation and structural relationship maintenance are directly encoded into the objective function. Beyond deforming a given multi-element 2D shape into a new one at each key frame, our method can automatically generate a sequence of natural intermediate deformations by interpolating the shapes between the key frames. The method is computationally efficient, allowing real-time manipulation and interpolation, as well as generating natural and visually plausible results.
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.
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.
Multi-scale Assemblage for Procedural Texturing
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Gilet, Guillaume; Dischler, Jean-Michel; Ghazanfarpour, Djamchid; C. Bregler, P. Sander, and M. Wimmer
A procedural pattern generation process, called multi-scale ''assemblage'' is introduced. An assemblage is defined as a multi-scale composition of ''multi-variate'' statistical figures, that can be kernel functions for defining noiselike texture basis functions, or that can be patterns for defining structured procedural textures. This paper presents two main contributions: 1) a new procedural random point distribution function, that, unlike point jittering, allow us to take into account some spatial dependencies among figures and 2) a ''multi-variate'' approach that, instead of defining finite sets of constant figures, allows us to generate nearly infinite variations of figures on-the-fly. For both, we use a ''statistical shape model'', which is a representation of shape variations. Thanks to a direct GPU implementation, assemblage textures can be used to generate new classes of procedural textures for real-time rendering by preserving all characteristics of usual procedural textures, namely: infinity, definition independency (provided the figures are also definition independent) and extreme compactness.

Browse

Browsing 31-Issue 7 by Issue Date

Results Per Page

Sort Options