EG2013

Permanent URI for this community

https://diglib.eg.org/handle/10.2312/298

Browse

Now showing 1 - 20 of 124

Accelerating kd-tree Searches for all k-nearest Neighbours
(The Eurographics Association, 2013) Merry, Bruce; Gain, James; Marais, Patrick; M.- A. Otaduy and O. Sorkine
Finding the k nearest neighbours of each point in a point cloud forms an integral part of many point-cloud processing tasks. One common approach is to build a kd-tree over the points and then iteratively query the k nearest neighbors of each point. We introduce a simple modification to these queries to exploit the coherence between successive points; no changes are required to the kd-tree data structure. The path from the root to the appropriate leaf is updated incrementally, and backtracking is done bottom-up. We show that this can reduce the time to compute the neighbourhood graph of a 3D point cloud by over 10%, and by up to 24% when k
Accurate Binary Image Selection from Inaccurate User Input
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Subr, Kartic; Paris, Sylvain; Soler, Cyril; Kautz, Jan; I. Navazo, P. Poulin
Selections are central to image editing, e.g., they are the starting point of common operations such as copy-pasting and local edits. Creating them by hand is particularly tedious and scribble-based techniques have been introduced to assist the process. By interpolating a few strokes specified by users, these methods generate precise selections. However, most of the algorithms assume a 100 percent accurate input, and even small inaccuracies in the scribbles often degrade the selection quality, which imposes an additional burden on users. In this paper, we propose a selection technique tolerant to input inaccuracies. We use a dense conditional random field (CRF) to robustly infer a selection from possibly inaccurate input. Further, we show that patch-based pixel similarity functions yield more precise selection than simple point-wise metrics. However, efficiently solving a dense CRF is only possible in low-dimensional Euclidean spaces, and the metrics that we use are high-dimensional and often non-Euclidean.We address this challenge by embedding pixels in a low-dimensional Euclidean space with a metric that approximates the desired similarity function. The results show that our approach performs better than previous techniques and that two options are sufficient to cover a variety of images depending on whether the objects are textured.
Adaptive Quantization Visibility Caching
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Popov, Stefan; Georgiev, Iliyan; Slusallek, Philipp; Dachsbacher, Carsten; I. Navazo, P. Poulin
Ray tracing has become a viable alternative to rasterization for interactive applications and also forms the basis of most global illumination methods. However, even today's fastest ray-tracers offer only a tight budget of rays per pixel per frame. Rendering performance can be improved by increasing this budget, or by developing methods that use it more efficiently. In this paper we propose a global visibility caching algorithm that reduces the number of shadow rays required for shading to a fraction of less than 2% in some cases. We quantize the visibility function's domain while ensuring a minimal degradation of the final image quality. To control the introduced error, we adapt the quantization locally, accounting for variations in geometry, sampling densities on both endpoints of the visibility queries, and the light signal itself. Compared to previous approaches for approximating visibility, e.g. shadow mapping, our method has several advantages: (1) it allows caching of arbitrary visibility queries between surface points and is thus applicable to all ray tracing based methods; (2) the approximation error is uniform over the entire image and can be bounded by a user-specified parameter; (3) the cache is created on-the-fly and does not waste any resources on queries that will never be used. We demonstrate the benefits of our method on Whitted-style ray tracing combined with instant radiosity, as well as an integration with bidirectional path tracing.
Adaptive Remeshing for Real-Time Mesh Deformation
(The Eurographics Association, 2013) Dunyach, Marion; Vanderhaeghe, David; Barthe, Loïc; Botsch, Mario; M.- A. Otaduy and O. Sorkine
We present an adaptive isotropic remeshing technique that is fast enough to be used in interactive applications, such as mesh deformation or mesh sculpting. Previous real-time remeshing techniques are either not adaptive, hence requiring too many triangles, or make compromises in terms of triangle quality. High quality adaptive remeshing techniques are too slow for interactive applications. In this short paper we present a simple extension of a uniform remeshing approach that results in an efficient, yet high quality, curvature-adaptive remeshing.
Analytic Rasterization of Curves with Polynomial Filters
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Manson, Josiah; Schaefer, Scott; I. Navazo, P. Poulin
We present a method of analytically rasterizing shapes that have curved boundaries and linear color gradients using piecewise polynomial prefilters. By transforming the convolution of filters with the image from an integral over area into a boundary integral, we find closed-form expressions for rasterizing shapes. We show that a polynomial expression can be used to rasterize any combination of polynomial curves and filters. Our rasterizer also handles rational quadratic boundaries, which allows us to evaluate circles and ellipses. We apply our technique to rasterizing vector graphics and show that our derivation gives an efficient implementation as a scanline rasterizer.
Analytic Visibility on the GPU
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Auzinger, Thomas; Wimmer, Michael; Jeschke, Stefan; I. Navazo, P. Poulin
This paper presents a parallel, implementation-friendly analytic visibility method for triangular meshes. Together with an analytic filter convolution, it allows for a fully analytic solution to anti-aliased 3D mesh rendering on parallel hardware. Building on recent works in computational geometry, we present a new edge-triangle intersection algorithm and a novel method to complete the boundaries of all visible triangle regions after a hidden line elimination step. All stages of the method are embarrassingly parallel and easily implementable on parallel hardware. A GPU implementation is discussed and performance characteristics of the method are shown and compared to traditional sampling-based rendering methods.
Animal Locomotion Controllers From Scratch
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Wampler, Kevin; Popovic, Jovan; Popovic, Zoran; I. Navazo, P. Poulin
There exists a large body of research devoted to creating real time interactive locomotion controllers which are targeted at some specific class of character, most often humanoid bipeds. Relatively little work, however, has been done on approaches which are applicable to creatures with a wide range of different forms - partially due to the lack of easily obtainable motion-capture data for animals and fictional creatures. We show how a locomotion controller can be created despite this dearth of data by synthesizing it from scratch. Our method only requires as input a description of the shape of the animal, the gaits which it can perform, and a model of the task or tasks for which the controller will be used. From this a sequence of motion clips are automatically synthesized and assembled into a motion graph which defines a physically realistic controller capable of performing the specified tasks. The method attempts to minimize the computational time required to generate this controller and we show its effectiveness at creating interactive controllers for a range of tasks for bipeds, tripeds, and quadrupeds.
ArtiSketch: A System for Articulated Sketch Modeling
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Levi, Zohar; Gotsman, Craig; I. Navazo, P. Poulin
We present ArtiSketch - a system which allows the conversion of a wealth of existing 2D content into 3D content by users who do not necessarily possess artistic skills. Using ArtiSketch, a novice user may describe a 3D model as a set of articulated 2D sketches of a shape from different viewpoints. ArtiSketch then automatically converts the sketches to an articulated 3D object. Using common interactive tools, the user provides an initial estimate of the 3D skeleton pose for each frame, which ArtiSketch refines to be consistent between frames. This skeleton may then be manipulated independently to generate novel poses of the 3D model.
Automatic Convergence Adjustment for Stereoscopy using Eye Tracking
(The Eurographics Association, 2013) Fisker, Martin; Gram, Kristoffer; Thomsen, Kasper Kronborg; Vasilarou, Dimitra; Kraus, Martin; Miguel Chover and A. Augusto de Sousa
When using stereoscopic displays, decoupling between convergence and accommodation can cause eyestrain. This paper proposes an adjustment method to automatically fit convergence at user fixation depth to accommodation by using eye tracking. Two different adjustment methods are proposed: one binocular, adjusting the images for both eyes, and one monocular, which adjusts only the image for the non-dominant eye. Preliminary results suggest better user comfort and a preference for binocular adjustment in high adjustment scenarios, while the adjustment is less noticeable with the monocular system.
Automatic Generation of Constructable Brick Sculptures
(The Eurographics Association, 2013) Testuz, Romain; Schwartzburg, Yuliy; Pauly, Mark; M.- A. Otaduy and O. Sorkine
Fabrication of LEGO R models in large scale requires careful pre-planning to produce constructable and stable models. We propose a system that, starting with a voxelization of a 3D mesh, merges voxels to form larger bricks, and then analyzes and repairs structural problems, finally outputting a set of building instructions. We also present extensions such as producing hollow models, fulfilling limits on the number of bricks of each size, and including colors. Results (both real and virtual) and timings show significant improvements over previous work.
Automatic Modeling of Planar-Hinged Buildings
(The Eurographics Association, 2013) Garcia-Dorado, Ignacio; Aliaga, Daniel G.; M.- A. Otaduy and O. Sorkine
We present a framework to automatically model and reconstruct buildings in a dense urban area. Our method is robust to noise and recovers planar features and sharp edges, producing a water-tight triangulation suitable for texture mapping and interactive rendering. Building and architectural priors, such as the Manhattan world and Atlanta world assumptions, have been used to improve the quality of reconstructions. We extend the framework to include buildings consisting of arbitrary planar faces interconnected by hinges. Given millions of initial 3D points and normals (i.e., via an image-based reconstruction), we estimate the location and properties of the building model hinges and planar segments. Then, starting with a closed Poisson triangulation, we use an energy-based metric to iteratively refine the initial model so as to attempt to recover the planar-hinged model and maintain building details where possible. Our results include automatically reconstructing a variety of buildings spanning a large and dense urban area, comparisons, and analysis of our method. The end product is an automatic method to produce watertight models that are very suitable for 3D city modeling and computer graphics applications.
Automatic Parameter Control for Metropolis Light Transport
(The Eurographics Association, 2013) Zsolnai, Károly; Szirmay-Kalos, László; M.- A. Otaduy and O. Sorkine
Sophisticated global illumination algorithms usually have several control parameters that need to be set appropriately in order to obtain high performance and accuracy. Unfortunately, the optimal values of these parameters are scene dependent, thus their setting is a cumbersome process that requires significant care and is usually based on trial and error. To address this problem, this paper presents a method to automatically control the large step probability parameter of Primary Sample Space Metropolis Light Transport (PSSMLT). The method does not require extra computation time or pre-processing, and runs in parallel with the initial phase of the rendering method. During this phase, it gathers statistics from the process and computes the parameters for the remaining part of the sample generation. We show that the theoretically proposed values are close to the manually found optimum for several complex scenes.
Bilateral Hermite Radial Basis Functions for Contour-based Volume Segmentation
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Ijiri, Takashi; Yoshizawa, Shin; Sato, Yu; Ito, Masaaki; Yokota, Hideo; I. Navazo, P. Poulin
In this paper, we propose a novel contour-based volume image segmentation technique. Our technique is based on an implicit surface reconstruction strategy, whereby a signed scalar field is generated from user-specified contours. The key idea is to compute the scalar field in a joint spatial-range domain (i.e., bilateral domain) and resample its values on an image manifold. We introduce a new formulation of Hermite radial basis function (HRBF) interpolation to obtain the scalar field in the bilateral domain. In contrast to previous implicit methods, bilateral HRBF (BHRBF) generates a segmentation boundary that passes through all contours, fits high-contrast image edges if they exist, and has a smooth shape in blurred areas of images. We also propose an acceleration scheme for computing B-HRBF to support a real-time and intuitive segmentation interface. In our experiments, we achieved high-quality segmentation results for regions of interest with high-contrast edges and blurred boundaries.
By-example Synthesis of Curvilinear Structured Patterns
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Zhou, Shizhe; Lasram, Anass; Lefebvre, Sylvain; I. Navazo, P. Poulin
Many algorithms in Computer Graphics require to synthesize a pattern along a curve. This is for instance the case with line stylization, to decorate objects with elaborate patterns (chains, laces, scratches), or to synthesize curvilinear features such as mountain ridges, rivers or roads. We describe a simple yet effective method for this problem. Our method addresses the main challenge of maintaining the continuity of the pattern while following the curve. It allows some freedom to the synthesized pattern: It may locally diverge from the curve so as to allow for a more natural global result. This also lets the pattern escape areas of overlaps or fold-overs. This makes our method particularly well suited to structured, detailed patterns following complex curves. Our synthesizer copies tilted pieces of the exemplar along the curve, following its orientation. The result is optimized through a shortest path search, with dynamic programming. We speed up the process by an efficient parallel implementation. Finally, since discontinuities may always remain we propose an optional post-processing step optimally deforming neighboring pieces to smooth the transitions.
Capture and Statistical Modeling of Arm-Muscle Deformations
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Neumann, Thomas; Varanasi, Kiran; Hasler, Nils; Wacker, Markus; Magnor, Marcus; Theobalt, Christian; I. Navazo, P. Poulin
We present a comprehensive data-driven statistical model for skin and muscle deformation of the human shoulderarm complex. Skin deformations arise from complex bio-physical effects such as non-linear elasticity of muscles, fat, and connective tissue; and vary with physiological constitution of the subjects and external forces applied during motion. Thus, they are hard to model by direct physical simulation. Our alternative approach is based on learning deformations from multiple subjects performing different exercises under varying external forces. We capture the training data through a novel multi-camera approach that is able to reconstruct fine-scale muscle detail in motion. The resulting reconstructions from several people are aligned into one common shape parametrization, and learned using a semi-parametric non-linear method. Our learned data-driven model is fast, compact and controllable with a small set of intuitive parameters - pose, body shape and external forces, through which a novice artist can interactively produce complex muscle deformations. Our method is able to capture and synthesize fine-scale muscle bulge effects to a greater level of realism than achieved previously. We provide quantitative and qualitative validation of our method.
Capturing Relightable Human Performances under General Uncontrolled Illumination
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Li, Guannan; Wu, Chenglei; Stoll, Carsten; Liu, Yebin; Varanasi, Kiran; Dai, Qionghai; Theobalt, Christian; I. Navazo, P. Poulin
We present a novel approach to create relightable free-viewpoint human performances from multi-view video recorded under general uncontrolled and uncalibated illumination.We first capture a multi-view sequence of an actor wearing arbitrary apparel and reconstruct a spatio-temporal coherent coarse 3D model of the performance using a marker-less tracking approach. Using these coarse reconstructions, we estimate the low-frequency component of the illumination in a spherical harmonics (SH) basis as well as the diffuse reflectance, and then utilize them to estimate the dynamic geometry detail of human actors based on shading cues. Given the high-quality time-varying geometry, the estimated illumination is extended to the all-frequency domain by re-estimating it in the wavelet basis. Finally, the high-quality all-frequency illumination is utilized to reconstruct the spatially-varying BRDF of the surface. The recovered time-varying surface geometry and spatially-varying non-Lambertian reflectance allow us to generate high-quality model-based free view-point videos of the actor under novel illumination conditions. Our method enables plausible reconstruction of relightable dynamic scene models without a complex controlled lighting apparatus, and opens up a path towards relightable performance capture in less constrained environments and using less complex acquisition setups.
Centers of Approximate Spherical Symmetry and Radial Symmetry Graphs
(The Eurographics Association, 2013) Giachetti, Andrea; Lovato, Christian; M.- A. Otaduy and O. Sorkine
In this paper we propose the possible use of a new type of salient points we call CASS (Centers of Approximate Spherical Symmetry) that are extracted from the Multiscale Area Projection transform described in [GL12]. In particular, we show that it is possible to build graphs joining these points following maximal values of the MAPT (Radial Symmetry Graphs) and that these graphs can be used to extract relevant shape properties (e.g. intrin- sic symmetries) or to establish point correspondences on models robustly against holes, topological noise and articulated deformations.
CIIG: Granada Graphics Group, Granada, Spain
(The Eurographics Association, 2013) Martin, D.; Torres, J. C.; J. C. Torres and A. Lecuyer
The Granada Graphics Group is one of the research groups of the Software System Department. It covers education and research activities on Comouter Graphics at the University of Granada.
Circular Arc Snakes and Kinematic Surface Generation
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Barton, Michael; Shi, Ling; Kilian, Martin; Wallner, Johannes; Pottmann, Helmut; I. Navazo, P. Poulin
We discuss the theory, discretization, and numerics of curves which are evolving such that part of their shape, or at least their curvature as a function of arc length, remains unchanged. The discretization of a curve as a smooth sequence of circular arcs is well suited for such purposes, and allows us to reduce evolution of curves to the evolution of a control point collection in a certain finite-dimensional shape space. We approach this evolution by a 2-step process: linearized evolution via optimized velocity fields, followed by optimization in order to exactly fulfill all geometric side conditions. We give applications to freeform architecture, including ''rationalization'' of a surface by congruent arcs, form finding and, most interestingly, non-static architecture.
Computational Displays: Combining Optical Fabrication, Computational Processing, and Perceptual Tricks to Build the Displays of the Future
(The Eurographics Association, 2013) Wetzstein, Gordon; Lanman, Douglas; Didyk, Piotr; Diego Gutierrez and Karol Myszkowski
With the invention of integral imaging and parallax barriers in the beginning of the 20th century, glasses-free 3D displays have become feasible. Only today -more than a century later- glasses-free 3D displays are finally emerging in the consumer market. The technologies being employed in current-generation devices, however, are fundamentally the same as what was invented 100 years ago. With rapid advances in optical fabrication, digital processing power, and computational models for human perception, a new generation of display technology is emerging: computational displays exploring the co-design of optical elements and computational processingwhile taking particular characteristics of the human visual system into account. This technology does not only encompass 3D displays, but also next-generation projection systems, high dynamic range displays, perceptually-driven devices, and computational probes. This tutorial serves as an introduction to the emerging field of computational displays. The pedagogical goal of this tutorial is to provide the audience with the tools necessary to expand their research endeavorsby providing step-by-step instructions on all aspects of computational displays: display optics, mathematical analysis, efficient computational processing, computational perception, and, most importantly, the effective combination of all these aspects. Specifically, we will discuss a wide variety of different applications and hardware setups of computational displays, including high dynamic range displays, advanced projection systems as well as glasses-free 3D display. The latter example, computational light field displays, will be discussed in detail. In the tutorial presentation, supplementary notes, and an accompanying website, we will provide source code that drives various display incarnations at real-time framerates, detailed instructions on how to fabricate novel displays from off-the-shelf components, and intuitive mathematical analyses that will make it easy for researchers with various backgrounds to get started in the emerging field of computational displays. We believe that computational display technology is one of the hottest" topics in the graphics community today; with this tutorial we will make it accessible for a diverse audience. This tutorial was previously taught as a course at SIGGRAPH 2012.We will discuss all aspects of computational displays in detail. Specifically,we begin by introducing the concept and discussing a variety of example displays that exploit the joint-design of optical components and computational processing for applications such as high dynamic range image and wide color gamut display, extended depth of field projection, and high-dimensional information display for computer vision applications. We will then proceed to discussing state-of-the-art computational light field displays in detail. In particular, we will focus on how high-speed displays, multiple stacked LCDs, and directional backlighting combined with advanced mathematical analysis and efficient computational processing provide the foundations of 3D displays of the future. Finally, we will review psycho-physiological aspects that are of importance for display design and demonstrate how perceptually-driven computational displays can enhance the capability of current technology.

Browse

Browsing EG2013 by Title

Results Per Page

Sort Options