Volume 29 (2010)

Permanent URI for this community

https://diglib.eg.org/handle/10.2312/151

Browse

Now showing 1 - 20 of 259

SoundRiver: Semantically-Rich Sound Illustration
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Jaenicke, H.; Borgo, R.; Mason, J. S. D.; Chen, M.
Sound is an integral part of most movies and videos. In many situations, viewers of a video are unable to hear the sound track, for example, when watching it in a fast forward mode, viewing it by hearing-impaired viewers or when the plot is given as a storyboard. In this paper, we present an automated visualization solution to such problems. The system first detects the common components (such as music, speech, rain, explosions, and so on) from a sound track, then maps them to a collection of programmable visual metaphors, and generates a composite visualization. This form of sound visualization, which is referred to as SoundRiver, can be also used to augment various forms of video abstraction and annotated key frames and to enhance graphical user interfaces for video handling software. The SoundRiver conveys more semantic information to the viewer than traditional graphical representations of sound illustration, such as phonoautographs, spectrograms or artistic audiovisual animations.
Real Time Animation of Virtual Humans: A Trade-off Between Naturalness and Control
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Van Welbergen, H.; Van Basten, B. J. H.; Egges, A.; Ruttkay, Zs. M.; Overmars, M. H.
Virtual humans are employed in many interactive applications using 3D virtual environments, including (serious) games. The motion of such virtual humans should look realistic (or natural and allow interaction with the surroundings and other (virtual) humans. Current animation techniques differ in the trade-off they offer between motion naturalness and the control that can be exerted over the motion. We show mechanisms to parametrize, combine (on different body parts) and concatenate motions generated by different animation techniques. We discuss several aspects of motion naturalness and show how it can be evaluated. We conclude by showing the promise of combinations of different animation paradigms to enhance both naturalness and control.
Interactive Rendering of Non-Constant, Refractive Media Using the Ray Equations of Gradient-Index Optics
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Cao, Chen; Ren, Zhong; Guo, Baining; Zhou, Kun
Existing algorithms can efficiently render refractive objects of constant refractive index. For a medium with a continuously varying index of refraction, most algorithms use the ray equation of geometric optics to compute piecewise-linear approximations of the non-linear rays. By assuming a constant refractive index within each tracing step, these methods often need a large number of small steps to generate satisfactory images. In this paper, we present a new approach for tracing non-constant, refractive media based on the ray equations of gradient-index optics. We show that in a medium of constant index gradient, the ray equation has a closed-form solution, and the intersection point between a ray and the medium boundaries can be efficiently computed using the bisection method. For general non-constant media, we model the refractive index as a piecewise-linear function and render the refraction by tracing the tetrahedron-based representation of the media. Our algorithm can be easily combined with existing rendering algorithms such as photon mapping to generate complex refractive caustics at interactive frame rates. We also derive analytic ray formulations for tracing mirages - a special gradient-index optical phenomenon.
Isosurface Similarity Maps
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Bruckner, Stefan; Möller, Torsten; G. Melancon, T. Munzner, and D. Weiskopf
In this paper, we introduce the concept of isosurface similarity maps for the visualization of volume data. Isosurface similarity maps present structural information of a volume data set by depicting similarities between individual isosurfaces quantified by a robust information-theoretic measure. Unlike conventional histograms, they are not based on the frequency of isovalues and/or derivatives and therefore provide complementary information. We demonstrate that this new representation can be used to guide transfer function design and visualization parameter specification. Furthermore, we use isosurface similarity to develop an automatic parameter-free method for identifying representative isovalues. Using real-world data sets, we show that isosurface similarity maps can be a useful addition to conventional classification techniques.
A Salience-based Quality Metric for Visualization
(The Eurographics Association and Blackwell Publishing Ltd., 2010) Jänicke, Heike; Chen, Min; G. Melancon, T. Munzner, and D. Weiskopf
Salience detection is a principle mechanism to facilitate visual attention. A good visualization guides the observer s attention to the relevant aspects of the representation. Hence, the distribution of salience over a visualization image is an essential measure of the quality of the visualization. We describe a method for computing such a metric for a visualization image in the context of a given dataset. We show how this technique can be used to analyze a visualization s salience, improve an existing visualization, and choose the best representation from a set of alternatives. The usefulness of this proposed metric is illustrated using examples from information visualization, volume visualization and flow visualization.
Video Painting via Motion Layer Manipulation
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Huang, Hua; Zhang, Lei; Fu, Tian-Nan
Temporal coherence is an important problem in Non-Photorealistic Rendering for videos. In this paper, we present a novel approach to enhance temporal coherence in video painting. Instead of painting on video frame, our approach first partitions the video into multiple motion layers, and then places the brush strokes on the layers to generate the painted imagery. The extracted motion layers consist of one background layer and several object layers in each frame. Then, background layers from all the frames are aligned into a panoramic image, on which brush strokes are placed to paint the background in one-shot. The strokes used to paint object layers are propagated frame by frame using smooth transformations defined by thin plate splines. Once the background and object layers are painted, they are projected back to each frame and blent to form the final painting results. Thanks to painting a single image, our approach can completely eliminate the flickering in background, and temporal coherence on object layers is also significantly enhanced due to the smooth transformation over frames. Additionally, by controlling the painting strokes on different layers, our approach is easy to generate painted video with multi-style. Experimental results show that our approach is both robust and efficient to generate plausible video painting.
Scalable Height Field Self-Shadowing
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Timonen, Ville; Westerholm, Jan
We present a new method suitable for general purpose graphics processing units to render self-shadows on dynamic height fields under dynamic light environments in real-time. Visibility for each point in the height field is determined as the exact horizon for a set of azimuthal directions in time linear in height field size and the number of directions. The surface is shaded using the horizon information and a high-resolution light environment extracted on-line from a high dynamic range cube map, allowing for detailed extended shadows. The desired accuracy for any geometric content and lighting complexity can be matched by choosing a suitable number of azimuthal directions. Our method is able to represent arbitrary features of both high- and low-frequency, unifying hard and soft shadowing. We achieve 23 fps on 1024x1024 height fields with 64 azimuthal directions under a 256x64 environment lighting on an Nvidia GTX 280 GPU.
Afrigraph: The African Computer Graphics Association and its Activities
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Gain, J.; Strasser, W.; Hardy, A.; Marais, P.
The Virtual Director: a Correlation-Based Online Viewing of Human Motion
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Assa, J.; Wolf, L.; Cohen-Or, D.
Automatic camera control for scenes depicting human motion is an imperative topic in motion capture base animation, computer games, and other animation based fields. This challenging control problem is complex and combines both geometric constraints, visibility requirements, and aesthetic elements. Therefore, existing optimization-based approaches for human action overview are often too demanding for online computation.In this paper, we introduce an effective automatic camera control which is extremely efficient and allows online performance. Rather than optimizing a complex quality measurement, at each time it selects one active camera from a multitude of cameras that render the dynamic scene. The selection is based on the correlation between each view stream and the human motion in the scene. Two factors allow for rapid selection among tens of candidate views in real-time, even for complex multi-character scenes: the efficient rendering of the multitude of view streams, and optimized calculations of the correlations using modified CCA. In addition to the method s simplicity and speed, it exhibits good agreement with both cinematic idioms and previous human motion camera control work. Our evaluations show that the method is able to cope with the challenges put forth by severe occlusions, multiple characters and complex scenes.
Modeling Complex Unfoliaged Trees from a Sparse Set of Images
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lopez, Luis D.; Ding, Yuanyuan; Yu, Jingyi
We present a novel image-based technique for modeling complex unfoliaged trees. Existing tree modeling tools either require capturing a large number of views for dense 3D reconstruction or rely on user inputs and botanic rules to synthesize natural-looking tree geometry. In this paper, we focus on faithfully recovering real instead of realistically-looking tree geometry from a sparse set of images. Our solution directly integrates 2D/3D tree topology as shape priors into the modeling process. For each input view, we first estimate a 2D skeleton graph from its matte image and then find a 2D skeleton tree from the graph by imposing tree topology. We develop a simple but effective technique for computing the optimal 3D skeleton tree most consistent with the 2D skeletons. For each edge in the 3D skeleton tree, we further apply volumetric reconstruction to recover its corresponding curved branch. Finally, we use piecewise cylinders to approximate each branch from the volumetric results. We demonstrate our framework on a variety of trees to illustrate the robustness and usefulness of our technique.
Fast High-Dimensional Filtering Using the Permutohedral Lattice
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Adams, Andrew; Baek, Jongmin; Davis, Myers Abraham
Many useful algorithms for processing images and geometry fall under the general framework of high-dimensional Gaussian filtering. This family of algorithms includes bilateral filtering and non-local means. We propose a new way to perform such filters using the permutohedral lattice, which tessellates high-dimensional space with uniform simplices. Our algorithm is the first implementation of a high-dimensional Gaussian filter that is both linear in input size and polynomial in dimensionality. Furthermore it is parameter-free, apart from the filter size, and achieves a consistently high accuracy relative to ground truth (> 45 dB). We use this to demonstrate a number of interactive-rate applications of filters in as high as eight dimensions.
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.
Globally Consistent Space-Time Reconstruction
(2010) Tiberiu Popa; Ian South-Dickinson; Derek Bradley; Alla Sheffer; Wolfgang Heidrich
Most objects deform gradually over time, without abrupt changes in geometry or topology, such as changes in genus. Correct space-time reconstruction of such objects should satisfy this gradual change prior. This requirement necessitates a globally consistent interpretation of spatial adjacency. Consider the capture of a surface that comes in contact with itself during the deformation process, such as a hand with different fingers touching one another in parts of the sequence. Naive reconstruction would glue the contact regions together for the duration of each contact and keep them apart in other parts of the sequence. However such reconstruction violates the gradual change prior as it enforces a drastic intrinsic change in the object's geometry at the transition between the glued and unglued sub-sequences. Instead consistent global reconstruction should keep the surfaces separate throughout the entire sequence. We introduce a new method for globally consistent space-time geometry and motion reconstruction from video capture. We use the gradual change prior to resolve inconsistencies and faithfully reconstruct the geometry and motion of the scanned objects. In contrast to most previous methods our algorithm doesn't require a strong shape prior such as a template and provides better results than other template-free approaches.
Bidirectional Search for Interactive Motion Synthesis
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Lo, Wan-Yen; Zwicker, Matthias
We present an approach to improve the search efficiency for near-optimal motion synthesis using motion graphs. An optimal or near-optimal path through a motion graph often leads to the most intuitive result. However, finding such a path can be computationally expensive. Our main contribution is a bidirectional search algorithm. We dynamically divide the search space evenly and merge two search trees to obtain the final solution. This cuts the maximum search depth almost in half and leads to significant speedup. To illustrate the benefits of our approach, we present an interactive sketching interface that allows users to specify complex motions quickly and intuitively.
Multi-Image Based Photon Tracing for Interactive Global Illumination of Dynamic Scenes
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Yao, Chunhui; Wang, Bin; Chan, Bin; Yong, Junhai; Paul, Jean-Claude
Image space photon mapping has the advantage of simple implementation on GPU without pre-computation of complex acceleration structures. However, existing approaches use only a single image for tracing caustic photons, so they are limited to computing only a part of the global illumination effects for very simple scenes. In this paper we fully extend the image space approach by using multiple environment maps for photon mapping computation to achieve interactive global illumination of dynamic complex scenes. The two key problems due to the introduction of multiple images are 1) selecting the images to ensure adequate scene coverage; and 2) reliably computing ray-geometry intersections with multiple images. We present effective solutions to these problems and show that, with multiple environment maps, the image-space photon mapping approach can achieve interactive global illumination of dynamic complex scenes. The advantages of the method are demonstrated by comparison with other existing interactive global illumination methods.
Deformation Transfer to Multi-Component Objects
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Zhou, Kun; Xu, Weiwei; Tong, Yiying; Desbrun, Mathieu
We present a simple and effective algorithm to transfer deformation between surface meshes with multiple components. The algorithm automatically computes spatial relationships between components of the target object, builds correspondences between source and target, and finally transfers deformation of the source onto the target while preserving cohesion between the target s components. We demonstrate the versatility of our approach on various complex models.
Poisson-Based Weight Reduction of Animated Meshes
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Landreneau, Eric; Schaefer, Scott
While animation using barycentric coordinates or other automatic weight assignment methods has become a popular method for shape deformation, the global nature of the weights limits their use for real-time applications. We present a method that reduces the number of control points influencing a vertex to a user-specified number such that the deformations created by the reduced weight set resemble that of the original deformation. To do so we show how to set up a Poisson minimization problem to solve for a reduced weight set and illustrate its advantages over other weight reduction methods. Not only does weight reduction lower the amount of storage space necessary to deform these models but also allows GPU acceleration of the resulting deformations. Our experiments show that we can achieve a factor of 100 increase in speed over CPU deformations using the full weight set, which makes real-time deformations of large models possible.
Rendering Wave Effects with Augmented Light Field
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Oh, Se Baek; Kashyap, Sriram; Garg, Rohit; Chandran, Sharat; Raskar, Ramesh
Ray-based representations can model complex light transport but are limited in modeling diffraction effects that require the simulation of wavefront propagation. This paper provides a new paradigm that has the simplicity of light path tracing and yet provides an accurate characterization of both Fresnel and Fraunhofer diffraction. We introduce the concept of a light field transformer at the interface of transmissive occluders. This generates mathematically sound, virtual, and possibly negative-valued light sources after the occluder. From a rendering perspective the only simple change is that radiance can be temporarily negative. We demonstrate the correctness of our approach both analytically, as well by comparing values with standard experiments in physics such as the Young s double slit. Our implementation is a shader program in OpenGL that can generate wave effects on arbitrary surfaces.
Mesh Snapping: Robust Interactive Mesh Cutting Using Fast Geodesic Curvature Flow
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Zhang, Juyong; Wu, Chunlin; Cai, Jianfei; Zheng, Jianmin; Tai, Xue-cheng
This paper considers the problem of interactively finding the cutting contour to extract components from a given mesh. Some existing methods support cuts of arbitrary shape but require careful and tedious input from the user. Others need little user input however they are sensitive to user input and need a postprocessing step to smooth the generated jaggy cutting contours. The popular geometric snake can be used to optimize the cutting contour, but it cannot deal with the topology change. In this paper, we propose a geodesic curvature flow based framework to overcome all these problems. Since in many cases the meaningful cutting contour on a 3D mesh is locally shortest in the sense of some weighted curve length, the geodesic curvature flow is an ideal tool for our problem. It evolves the cutting contour to the nearby local minimum. We should mention that the previous numerical scheme, discretized geodesic curvature flow (dGCF) is too slow and has not been applied to mesh segmentation. With a careful observation to dGCF, we devise here a fast computation scheme called fast geodesic curvature flow (FGCF), which only needs to solve a smaller and easier problem. The initial cutting contour is generated by a variant of random walks algorithm, which is very fast and gives reasonable cutting result with little user input. Experiment results on the benchmark mesh segmentation data set show that our proposed framework is robust to user input and capable of producing good results reflecting geometric features and human shape perception.
An Eyeglass Simulator Using Conoid Tracing
(The Eurographics Association and Blackwell Publishing Ltd, 2010) Kakimoto, M.; Tatsukawa, T.; Nishita, T.
This paper proposes a method for displaying images at the fovea of the retina taking visual acuity into account. Previous research has shown that a point light source projected onto the retina forms an ellipse, which can be computed with wavefront tracing from each point in space. We propose a novel concept using conoid tracing, with which we can acquire defocusing information several times faster than that acquired by previous methods. We also show that conoid tracing is more robust and produces higher quality results. In conoid tracing the ray is regarded as a conoid, a thin cone-like shape with varying elliptical cross-section. The viewing ray from the retina is traced as a conoid and evaluated at each sample location. Using the sampled and pre-computed data for the spatial distribution of blurring, we implemented an interactive eyeglass simulator. This paper demonstrates some visualization results utilizing the interactivity of the simulator, which an eyeglass lens design company uses to evaluate the design of complex progressive lenses.

Browse

Browsing Volume 29 (2010) by Issue Date

Results Per Page

Sort Options