29-Issue 7

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/158

Browse

Now showing 1 - 20 of 32

Automatic Animation for Time-Varying Data Visualization
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Yu, Li; Lu, Aidong; Ribarsky, William; Chen, Wei
This paper presents a digital storytelling approach that generates automatic animations for time-varying data visualization. Our approach simulates the composition and transition of storytelling techniques and synthesizes animations to describe various event features. Specifically, we analyze information related to a given event and abstract it as an event graph, which represents data features as nodes and event relationships as links. This graph embeds a tree-like hierarchical structure which encodes data features at different scales. Next, narrative structures are built by exploring starting nodes and suitable search strategies in this graph. Different stages of narrative structures are considered in our automatic rendering parameter decision process to generate animations as digital stories. We integrate this animation generation approach into an interactive exploration process of time-varying data, so that more comprehensive information can be provided in a timely fashion. We demonstrate with a storm surge application that our approach allows semantic visualization of time-varying data and easy animation generation for users without special knowledge about the underlying visualization techniques.
B-Mesh: A Modeling System for Base Meshes of 3D Articulated Shapes
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Ji, Zhongping; Liu, Ligang; Wang, Yigang
This paper presents a novel modeling system, called B-Mesh, for generating base meshes of 3D articulated shapes. The user only needs to draw a one-dimensional skeleton and to specify key balls at the skeletal nodes. The system then automatically generates a quad dominant initial mesh. Further subdivision and evolution are performed to refine the initial mesh and generate a quad mesh which has good edge flow along the skeleton directions. The user can also modify and manipulate the shape by editing the skeleton and the key balls and can easily compose new shapes by cutting and pasting existing models in our system. The mesh models generated in our system greatly benefit the sculpting operators for sculpting modeling and skeleton-based animation.
Binary Orientation Trees for Volume and Surface Reconstruction from Unoriented Point Clouds
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Chen, Yi-Ling; Chen, Bing-Yu; Lai, Shang-Hong; Nishita, Tomoyuki
Given a complete unoriented point set, we propose a binary orientation tree (BOT) for volume and surface representation, which roughly splits the space into the interior and exterior regions with respect to the input point set. The BOTs are constructed by performing a traditional octree subdivision technique while the corners of each cell are associated with a tag indicating the in/out relationship with respect to the input point set. Starting from the root cell, a growing stage is performed to efficiently assign tags to the connected empty sub-cells. The unresolved tags of the remaining cell corners are determined by examining their visibility via the hidden point removal operator. We show that the outliers accompanying the input point set can be effectively detected during the construction of the BOTs. After removing the outliers and resolving the in/out tags, the BOTs are ready to support any volume or surface representation techniques. To represent the surfaces, we also present a modified MPU implicits algorithm enabled to reconstruct surfaces from the input unoriented point clouds by taking advantage of the BOTs.
Condenser-Based Instant Reflectometry
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lan, Yanxiang; Dong, Yue; Wang, Jiaping; Tong, Xin; Guo, Baining
We present a technique for rapid capture of high quality bidirectional reflection distribution functions(BRDFs) of surface points. Our method represents the BRDF at each point by a generalized microfacet model with tabulated normal distribution function (NDF) and assumes that the BRDF is symmetrical. A compact and light-weight reflectometry apparatus is developed for capturing reflectance data from each surface point within one second. The device consists of a pair of condenser lenses, a video camera, and six LED light sources. During capture, the reflected rays from a surface point lit by a LED lighting are refracted by a condenser lenses and efficiently collected by the camera CCD. Taking advantage of BRDF symmetry, our reflectometry apparatus provides an efficient optical design to improve the measurement quality. We also propose a model fitting algorithm for reconstructing the generalized microfacet model from the sparse BRDF slices captured from a material surface point. Our new algorithm addresses the measurement errors and generates more accurate results than previous work. Our technique provides a practical and efficient solution for BRDF acquisition, especially for materials with anisotropic reflectance. We test the accuracy of our approach by comparing our results with ground truth. We demonstrate the efficiency of our reflectometry by measuring materials with different degrees of specularity, values of Fresnel factor, and angular variation.
Context-Dependent Crowd Evaluation
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lerner, Alon; Chrysanthou, Yiorgos; Shamir, Ariel; Cohen-Or, Daniel
Many times, even if a crowd simulation looks good in general, there could be some specific individual behaviors which do not seem correct. Spotting such problems manually can become tedious, but ignoring them may harm the simulation s credibility. In this paper we present a data-driven approach for evaluating the behaviors of individuals within a simulated crowd. Based on video-footage of a real crowd, a database of behavior examples is generated. Given a simulation of a crowd, an analog analysis is performed on it, defining a set of queries, which are matched by a similarity function to the database examples. The results offer a possible objective answer to the question of how similar are the simulated individual behaviors to real observed behaviors. Moreover, by changing the video input one can change the context of evaluation. We show several examples of evaluating simulated crowds produced using different techniques and comprising of dense crowds, sparse crowds and flocks.
Contour-based Interface for Refining Volume Segmentation
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Ijiri, Takashi; Yokota, Hideo
Medical volume images contain ambiguous and low-contrast boundaries around which existing fully- or semiautomatic segmentation algorithms often cause errors. In this paper, we propose a novel system for intuitively and efficiently refining medical volume segmentation by modifying multiple curved contours. Starting with segmentation data obtained using any existing algorithm, the user places a three-dimensional curved cross-section and contours of the foreground region by drawing a cut stroke, and then modifies the contours referring to the cross-section. The modified contours are used as constraints for deforming a boundary surface that envelops the foreground region, and the region is updated by that deformed boundary. Our surface deformation algorithm seamlessly integrates detail-preserving and curvature-diffusing methods to keep important detail boundary features intact while obtaining smooth surfaces around unimportant boundary regions. Our system supports topological manipulations as well as contour shape modifications. We illustrate the feasibility of our system by providing examples of its application to the extraction of bones, muscles, kidneys with blood vessels, and bowels.
Creating and Preserving Vortical Details in SPH Fluid
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Zhu, Bo; Yang, Xubo; Fan, Ye
We present a new method to create and preserve the turbulent details generated around moving objects in SPH fluid. In our approach, a high-resolution overlapping grid is bounded to each object and translates with the object. The turbulence formation is modeled by resolving the local flow around objects using a hybrid SPH-FLIP method. Then these vortical details are carried on SPH particles flowing through the local region and preserved in the global field in a synthetic way. Our method provides a physically plausible way to model the turbulent details around both rigid and deformable objects in SPH fluid, and can efficiently produce animations of complex gaseous phenomena with rich visual details.
Density-based Outlier Rejection in Monte Carlo Rendering
(The Eurographics Association and Blackwell Publishing Ltd, 2010) DeCoro, Christopher; Weyrich, Tim; Rusinkiewicz, Szymon
The problem of noise in Monte-Carlo rendering arising from estimator variance is well-known and well-studied. In this work, we concentrate on identifying individual light paths as outliers that lead to significant spikes of noise and represent a challenge for existing filtering methods. Most noise-reduction methods, such as importance sampling and stratification, attempt to generate samples that are expected a priori to have lower variance, but do not take into account actual sample values. While these methods are essential to decrease overall noise, we show that filtering samples a posteriori allows for greater reduction of spiked noise. In particular, given evaluated sample values, outliers can be identified and removed. Conforming with conventions in statistics, we emphasize that the term outlier should not be taken as synonymous with incorrect , but as referring to samples that distort the empirically-observed distribution of energy relative to the true underlying distribution. By expressing a path distribution in joint image and color space, we show how outliers can be characterized by their density across the set of all nearby paths in this space. We show that removing these outliers leads to significant improvements in rendering quality.
Dirichlet Harmonic Shape Compression with Feature Preservation for Parameterized Surfaces
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Liu, Yang; Prabhakaran, Balakrishnan; Guo, Xiaohu
With the rapid advancement of 3D scanning devices, large and complicated 3D shapes are becoming ubiquitous, and require large amount of resources to store and transmit them efficiently. This makes shape compression a demanding technique in order for the user to reduce the data transmission latency. Existing shape compression methods could achieve very low bit-rates by sacrificing shape quality. But none of them guarantees the preservation of salient feature lines that users care. In addition, many 3D shapes come with parametric information for texture mapping purposes. In this paper we describe a spectral method to compress the geometric shapes equipped with arbitrary valid parametric information. It guarantees to preserve user-specified feature lines while achieving a high compression ratio. By applying the spectral shape analysis - Dirichlet Manifold Harmonics, in the 2D parametric domain, this method provides a progressive compression mechanism to trade-off between bit-rate and shape quality. Experiments show that this method provides very low bit-rate with high shape-quality and still guarantees the preservation of user-specified feature lines.
Efficient Mean-shift Clustering Using Gaussian KD-Tree
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Xiao, Chunxia; Liu, Meng
Mean shift is a popular approach for data clustering, however, the high computational complexity of the mean shift procedure limits its practical applications in high dimensional and large data set clustering. In this paper, we propose an efficient method that allows mean shift clustering performed on large data set containing tens of millions of points at interactive rate. The key in our method is a new scheme for approximating mean shift procedure using a greatly reduced feature space. This reduced feature space is adaptive clustering of the original data set, and is generated by applying adaptive KD-tree in a high-dimensional affinity space. The proposed method significantly reduces the computational cost while obtaining almost the same clustering results as the standard mean shift procedure. We present several kinds of data clustering applications to illustrate the efficiency of the proposed method, including image and video segmentation, static geometry model and time-varying sequences segmentation.
An Example-based Approach to Synthesize Artistic Strokes using Graphs
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Kim, Mikyung; Shin, Hyun Joon
In this paper, we propose a technique to produce artistic strokes in a variety of drawing material based on example images. Our approach is to divide example strokes scanned from images into small pieces along their stroke directions and synthesize a novel stroke by rearranging them along a user specified curve. The visible quality of a synthesized stroke can be maintained by utilizing the connectivity information stored in a directed graph constructed in the preprocessing step. At run-time, the graph is traversed to find a path best matching the user specification given as a curve and additional information. The results of our experiments shows that visually convincing strokes of various materials can be generated efficiently.
Fast Particle-based Visual Simulation of Ice Melting
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Iwasaki, K.; Uchida, H.; Dobashi, Y.; Nishita, T.
The visual simulation of natural phenomena has been widely studied. Although several methods have been proposed to simulate melting, the flows of meltwater drops on the surfaces of objects are not taken into account. In this paper, we propose a particle-based method for the simulation of the melting and freezing of ice objects and the interactions between ice and fluids. To simulate the flow of meltwater on ice and the formation of water droplets, a simple interfacial tension is proposed, which can be easily incorporated into common particle-based simulation methods such as Smoothed Particle Hydrodynamics. The computations of heat transfer, the phase transition between ice and water, the interactions between ice and fluids, and the separation of ice due to melting are further accelerated by implementing our method using CUDA. We demonstrate our simulation and rendering method for depicting melting ice at interactive frame-rates.
Fast Updating of Delaunay Triangulation of Moving Points by Bi-cell Filtering
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Zhou, Yuanfeng; Sun, Feng; Wang, Wenping; Wang, Jiaye; Zhang, Caiming
Updating a Delaunay triangulation when data points are slightly moved is the bottleneck of computation time in variational methods for mesh generation and remeshing. Utilizing the connectivity coherence between two consecutive Delaunay triangulations for computation speedup is the key to solving this problem. Our contribution is an effective filtering technique that confirms most bi-cells whose Delaunay connectivities remain unchanged after the points are perturbed. Based on bi-cell flipping, we present an efficient algorithm for updating two-dimensional and three-dimensional Delaunay triangulations of dynamic point sets. Experimental results show that our algorithm outperforms previous methods.
Feature based terrain generation using diffusion equation
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Hnaidi, Houssam; Guerin, Eric; Akkouche, Samir; Peytavie, Adrien; Galin, Eric
This paper presents a diffusion method for generating terrains from a set of parameterized curves that characterize the landform features such as ridge lines, riverbeds or cliffs. Our approach provides the user with an intuitive vector-based feature-oriented control over the terrain. Different types of constraints (such as elevation, slope angle and roughness) can be attached to the curves so as to define the shape of the terrain. The terrain is generated from the curve representation by using an efficient multigrid diffusion algorithm. The algorithm can be efficiently implemented on the GPU, which allows the user to interactively create a vast variety of landscapes.
Feature Oriented Progressive Lossless Mesh Coding
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Peng, Jingliang; Huang, Yan; Kuo, C.-C. Jay; Eckstein, Ilya; Gopi, M.
A feature-oriented generic progressive lossless mesh coder (FOLProM) is proposed to encode triangular meshes with arbitrarily complex geometry and topology. In this work, a sequence of levels of detail (LODs) are generated through iterative vertex set split and bounding volume subdivision. The incremental geometry and connectivity updates associated with each vertex set split and/or bounding volume subdivision are entropy coded. Due to the visual importance of sharp geometric features, the whole geometry coding process is optimized for a better presentation of geometric features, especially at low coding bitrates. Feature-oriented optimization in FOLProM is performed in hierarchy control and adaptive quantization. Efficient coordinate representation and prediction schemes are employed to reduce the entropy of data significantly. Furthermore, a simple yet efficient connectivity coding scheme is proposed. It is shown that FOLProM offers a significant rate-distortion (R-D) gain over the prior art, which is especially obvious at low bitrates.
Frontmatter PG 2010
(The Eurographics Association and Blackwell Publishing Ltd, 2010)
Image Synthesis for Branching Structures
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Sibbing, Dominik; Pavic, Darko; Kobbelt, Leif
We present a set of techniques for the synthesis of artificial images that depict branching structures like rivers, cracks, lightning, mountain ranges, or blood vessels. The central idea is to build a statistical model that captures the characteristic bending and branching structure from example images. Then a new skeleton structure is synthesized and the final output image is composed from image fragments of the original input images. The synthesis part of our algorithm runs mostly automatic but it optionally allows the user to control the process in order to achieve a specific result. The combination of the statistical bending and branching model with sophisticated fragment-based image synthesis corresponds to a multi-resolution decomposition of the underlying branching structure into the low frequency behavior (captured by the statistical model) and the high frequency detail (captured by the image detail in the fragments). This approach allows for the synthesis of realistic branching structures, while at the same time preserving important textural details from the original image.
Instant Propagation of Sparse Edits on Images and Videos
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Li, Yong; Ju, Tao; Hu, Shi-Min
The ability to quickly and intuitively edit digital contents has become increasingly important in our everyday life. We propose a novel method for propagating a sparse set of user edits (e.g., changes in color, brightness, contrast, etc.) expressed as casual strokes to nearby regions in an image or video with similar appearances. Existing methods for edit propagation are typically based on optimization, whose computational cost can be prohibitive for large inputs. We re-formulate propagation as a function interpolation problem in a high-dimensional space, which we solve very efficiently using radial basis functions. While simple to implement, our method significantly improves the speed and space cost of existing methods, and provides instant feedback of propagation results even on large images and videos.
L4RW: Laziness-based Realistic Real-time Responsive Rebalance in Walking
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Xu, Mingliang; Li, Huansen; Lv, Pei; Chen, Wenzhi; Liu, Gengdai; Zhu, Pengyu; Pan, Zhigeng
We present a novel L4RW (Laziness-based Realistic Real-time Responsive Rebalance in Walking) technique to synthesize 4RW animations under unexpected external perturbations with minimal locomotion effort. We first devise a lazy dynamic rebalance model, which specifies the dynamic balance conditions, defines the rebalance effort, and selects the suitable rebalance strategy automatically using the laziness law after an unexpected perturbation. Based on the model, L4RW searches over a motion capture (mocap) database for an appropriate motion segment to follow, and the transition-to motions is generated by interpolating the active response dynamic motion. A support vector machine (SVM) based training, classification, and predication algorithm is applied to reduce the search space, and it is trained offline only once. Our algorithm classifies the mocap database into many rebalance strategy-specified subsets and then online predicts responsive motions in the subset according to the selected strategy. The rebalance effort, the extrapolated center of mass (XCoM) and environment constraints are selected as feature attributes for the SVM feature vector. Furthermore, the subset s segments are sorted through the rebalance effort, then our algorithm searches for an acceptable segment starting from the least-effort segment. Compared with previous methods, our search increases speed by over two orders of magnitude, and our algorithm creates more realistic and smooth 4RW animation.
Least Squares Subdivision Surfaces
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Boye, S.; Guennebaud, G.; Schlick, C.
The usual approach to design subdivision schemes for curves and surfaces basically consists in combining proper rules for regular configurations, with some specific heuristics to handle extraordinary vertices. In this paper, we introduce an alternative approach, called Least Squares Subdivision Surfaces (LS), where the key idea is to iteratively project each vertex onto a local approximation of the current polygonal mesh. While the resulting procedure haves the same complexity as simpler subdivision schemes, our method offers much higher visual quality, especially in the vicinity of extraordinary vertices. Moreover, we show it can be easily generalized to support boundaries and creases. The fitting procedure allows for a local control of the surface from the normals, making LS3 very well suited for interactive freeform modeling applications. We demonstrate our approach on diadic triangular and quadrangular refinement schemes, though it can be applied to any splitting strategies.

Browse

Browsing 29-Issue 7 by Title

Results Per Page

Sort Options