EG2011

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https://diglib.eg.org/handle/10.2312/284

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High-Quality Tactile Paintings
(The Eurographics Association, 2011) Reichinger, A.; Maierhofer, S.; Purgathofer, W.; A. Day and R. Mantiuk and E. Reinhard and R. Scopigno
The aim of this work is to bring the cultural heritage of two-dimensional art closer to being accessible by blind and visually impaired people. We present a computer-assisted workflow for the creation of tactile representations of paintings, suitable to be used as a learning tool in the context of guided tours in museums or galleries. Starting from high-resolution images of original paintings, our process allows an artist to quickly design the desired form, and generate data suitable for rapid prototyping machines to produce the physical touch tools. Laser-cut layered depth diagrams, convey not only the individual objects in the painting and their spatial layout, but also augment their depth relations. CNC-milled textured reliefs additionally render fine details like brush strokes and texture suitable for the sense of touch. Our methods mimic aspects of the visual sense, make sure that the haptic output is quite faithful to the original paintings and do not require special manual abilities, like sculpting skills.
Fast Hydraulic and Thermal Erosion on GPU
(The Eurographics Association, 2011) Jákó, Balázs; Tóth, Balázs; N. Avis and S. Lefebvre
Computer games, simulators and many other computer graphics applications display external scenes where a realistic looking terrain is a vital part of the view. In this paper we propose a method that generates realistic virtual terrains by simulation of hydraulic and thermal erosion on a predefined heightfield. The model is designed to be executed interactively on parallel architectures like graphics processors.
Reconstruction of Cultural Heritage Object Utilizing its Paper Model for Augmented Reality
(The Eurographics Association, 2011) Haladova, Zuzana; R. Laramee and I. S. Lim
Augmented reality is nowadays one of the most expanding fields of the computer graphics and the popularity of the cultural heritage AR applications increases as well. This project presents the reconstruction of the historical event with the augmented reality information added to the paper model of the heritage site. The application presents the fire of the Bojnice castle. The hardware used in the project consists of the web cam which records the scene with the castle and the computer which receives the record and produces the augmented experience. The two methods for the registration of the real model and the future work needed are presented.
Efficient Feature-preserving Local Projection Operator for Geometry Reconstruction
(The Eurographics Association, 2011) Liao, Bin; Xiao, Chunxia; Jin, Liqiang; N. Avis and S. Lefebvre
This paper proposes an efficient and feature-preserving locally optimal projection operator (FLOP) for geometry reconstruction. We first develop a bilateral weighted local optimal projection operator. We then present a novel fast FLOP operator based on random sampling of Kernel Density Estimate (KDE), which greatly accelerates FLOP. The experimental results show that the proposed algorithms are efficient and robust for feature-preserving geometry reconstruction.
Feature-Based Mesh Editing
(The Eurographics Association, 2011) Zhou, Qingnan; Weinkauf, Tino; Sorkine, Olga; N. Avis and S. Lefebvre
Editing and deformation of irregular meshes have become standard tools in geometric modeling. Most approaches try to preserve low-level differential properties of the surface during editing, whereas the global structure and shape of the features are not explicitly taken into account. In this paper, we introduce a feature-driven editing approach that puts global structural properties of the shape into the center of attention. We start by segmenting the mesh by ridges and valleys and use the so-defined curves and surface regions as intuitive handles for all subsequent editing operations. Our framework supports manipulations the positions and curvature values of the handles and the various mesh regions. In order to preserve the existing features, prevent unwanted appearance of new features, and maintain or manipulate global aspects of the shape, we apply curvature optimization in the affected areas. We show that the combination of feature extraction and curvature optimization leads to an intuitive modeling tool for high-quality surface manipulation.
User Manual on Augmented Reality for Installation and Maintenance of the V-Brakes System of a Mountain Bike
(The Eurographics Association, 2011) Martín-Gutiérrez, Jorge; Contero, Manuel; R. Laramee and I. S. Lim
Until now most traces of AR in applications related to mechanic and maintenance tasks has been performed in very specific systems which could be regarded as quite complex in the field they have been applied to (aircrafts, military equipment, etc.) In this paper we intend making this technology approachable for task and applications more common to everybody. We propose making one of the most frequent maintenance tasks in mountain bikes which is the installation of the brakes system and cartridge shoes as well as adjustment of the tension cable. They are not difficult tasks but making them the first few times may be quite tough for the average user. Therefore, we propose an easy interface based on augmented reality which fitted to the bike handlebars will guide the user step by step through installation of the V-brakes system, change of cartridge shoes and adjustment of tension cable. Interface is based in several cards containing markers with codified sequences based in 3D models for performing maintenance. User will use a mobile phone with camera or a head mounted display (HMD) connected to a PC so he may visualize the animated 3D models of pieces and tools needed for this operation. Virtual objects will be superimposed over the real ones so positions of each piece can be identified by the user before handling them. Final target is including the markers interface with the bike or brakes in their original purchase or making it available for download from a PC via web or as a mobile application.
Improving BVH Ray Tracing Speed Using the AVX Instruction Set
(The Eurographics Association, 2011) Áfra, Attila T.; R. Laramee and I. S. Lim
High performance ray tracing on the CPU requires the efficient utilization of SIMD instructions. Ray packet and ray stream traversal algorithms achieve this by performing computations on multiple rays, nodes, or primitives at the same time. In this paper, we present our approach to optimizing coherent BVH ray packet tracing for the new AVX instruction set, which enables 8-wide SIMD operations on 32-bit floating-point numbers. We have measured an average speedup of about 50 percent compared to our SSE4.1 implementation, on an Intel Sandy Bridge processor.
Acoustic Rendering and Auditory-Visual Cross-Modal Perception and Interaction
(The Eurographics Association, 2011) Hulusic, Vedad; Harvey, Carlo; Tsingos, Nicolas; Debattista, Kurt; Walker, Steve; Howard, David; Chalmers, Alan; N. John and B. Wyvill
In recent years research in the 3-Dimensional sound generation field has been primarily focussed upon new applications of spatialised sound. In the computer graphics community the use of such techniques is most commonly found being applied to virtual, immersive environments. However, the field is more varied and diverse than this and other research tackles the problem in a more complete, and computationally expensive manner. However, simulation of light and sound wave propagation is still unachievable at a physically accurate spatio-temporal quality in real-time. Although the Human Visual System (HVS) and the Human Auditory System (HAS) are exceptionally sophisticated, they also contain certain perceptional and attentional limitations. Researchers, in fields such as psychology, have been investigating these limitations for several years and have come up with some findings which may be exploited in other fields. This STAR provides a comprehensive overview of the major techniques for generating spatialised sound and, in addition, discusses perceptual and cross-modal influences to consider. We also describe current limitations and provide an in-depth look at the emerging topics in the field.
Enhancement of Low Dynamic Range Videos using High Dynamic Range Backgrounds
(The Eurographics Association, 2011) Banterle, Francesco; Dellepiane, Matteo; Scopigno, Roberto; A. Day and R. Mantiuk and E. Reinhard and R. Scopigno
In this paper, we present a practical system for enhancing the quality of Low Dynamic Range (LDR) videos using High Dynamic Range (HDR) background images. Our technique relies on the assumption that the HDR information is static in the video footage. This assumption can be valid in many scenarios where moving subjects are the main focus of the footage and do not have to interact with moving light sources or highly reflective objects. Another valid scenario is teleconferencing via webcams, where the background is typically over-exposed, not allowing the users to perceive correctly the environment where the communication is happening.
Artistic Stylisation of Images and Video
(The Eurographics Association, 2011) Collomosse, John; Kyprianidis, Jan Eric; Ralph Martin and Juan Carlos Torres
The half-day tutorial provides an introduction to Non- Photorealistic Rendering (NPR), targeted at both students and experienced researchers of Computer Graphics who have not previously explored NPR in their work. The tutorial focuses on two-dimensional (2D) NPR, specifically the transformation of photos or videos into synthetic art concepts will be introduced gently and no prior knowledge is assumed beyond a working knowledge of filtering and convolution operations. Some elements of the course will touch upon GPU implementation, but GPU concepts will be described at a high level of abstraction without need for detailed working knowledge of GPU programming.
Rendering with Layered Materials
(The Eurographics Association, 2011) Wilkie, Alexander; Weidlich, Andrea; Ralph Martin and Juan Carlos Torres
Abstract to follow.
Learning How to Match Fresco Fragments
(The Eurographics Association, 2011) Funkhouser, T.; Shin, H.; Toler-Franklin, C.; Castañeda, A. García; Brown, B.; Dobkin, D.; Rusinkiewicz, S.; Weyrich, T.; A. Day and R. Mantiuk and E. Reinhard and R. Scopigno
One of the main problems faced during reconstruction of fractured archaeological artifacts is sorting through a large number of candidate matches between fragments to find the relatively few that are correct. Previous computer methods for this task provided scoring functions based on a variety of properties of potential matches, including color and geometric compatibility across fracture surfaces. However, they usually consider only one or at most a few properties at once, and therefore provide match predictions with very low precision. In this paper, we investigate a machine learning approach that computes the probability that a match is correct based on the combination of many features. We explore this machine learning approach for ranking matches in three different sets of fresco fragments, finding that classifiers based on many match properties can be significantly more effective at ranking proposed matches than scores based on any single property alone. Our results suggest that it is possible to train a classifier on match properties in one data set and then use it to rank predicted matches in another data set effectively. We believe that this approach could be helpful in a variety of cultural heritage reconstruction systems.
AA Patterns
(The Eurographics Association, 2011) Ahmed, Abdalla G. M.; R. Laramee and I. S. Lim
AA Patterns is the name of a recently developed algorithmic art technique that employs a simple linear 2D transform to generate ornamental patterns of pixels. The patterns are controlled by a single real parameter between 1 and 2. By appropriately anatomizing this parameter it is shown that this single parameter actually allows much control over the patterns. Some potential uses are pointed out, too.
Comprehensive Facial Performance Capture
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Fyffe, Graham; Hawkins, Tim; Watts, Chris; Ma, Wan-Chun; Debevec, Paul; M. Chen and O. Deussen
We present a system for recording a live dynamic facial performance, capturing highly detailed geometry and spatially varying diffuse and specular reflectance information for each frame of the performance. The result is a reproduction of the performance that can be rendered from novel viewpoints and novel lighting conditions, achieving photorealistic integration into any virtual environment. Dynamic performances are captured directly, without the need for any template geometry or static geometry scans, and processing is completely automatic, requiring no human input or guidance. Our key contributions are a heuristic for estimating facial reflectance information from gradient illumination photographs, and a geometry optimization framework that maximizes a principled likelihood function combining multi-view stereo correspondence and photometric stereo, using multiresolution belief propagation. The output of our system is a sequence of geometries and reflectance maps, suitable for rendering in off-the-shelf software. We show results from our system rendered under novel viewpoints and lighting conditions, and validate our results by demonstrating a close match to ground truth photographs
Implicit Brushes for Stylized Line-based Rendering
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Vergne, Romain; Vanderhaeghe, David; Chen, Jiazhou; Barla, Pascal; Granier, Xavier; Schlick, Christophe; M. Chen and O. Deussen
We introduce a new technique called Implicit Brushes to render animated 3D scenes with stylized lines in realtime with temporal coherence. An Implicit Brush is defined at a given pixel by the convolution of a brush footprint along a feature skeleton; the skeleton itself is obtained by locating surface features in the pixel neighborhood. Features are identified via image-space fitting techniques that not only extract their location, but also their profile, which permits to distinguish between sharp and smooth features. Profile parameters are then mapped to stylistic parameters such as brush orientation, size or opacity to give rise to a wide range of line-based styles.
Walking On Broken Mesh: Defect-Tolerant Geodesic Distances and Parameterizations
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Campen, Marcel; Kobbelt, Leif; M. Chen and O. Deussen
Efficient methods to compute intrinsic distances and geodesic paths have been presented for various types of surface representations, most importantly polygon meshes. These meshes are usually assumed to be well-structured and manifold. In practice, however, they often contain defects like holes, gaps, degeneracies, non-manifold configurations - or they might even be just a soup of polygons. The task of repairing these defects is computationally complex and in many cases exhibits various ambiguities demanding tedious manual efforts. We present a computational framework that enables the computation of meaningful approximate intrinsic distances and geodesic paths on raw meshes in a way which is tolerant to such defects. Holes and gaps are bridged up to a user-specified tolerance threshold such that distances can be computed plausibly even across multiple connected components of inconsistent meshes. Further, we show ways to locally parameterize a surface based on geodesic distance fields, easily facilitating the application of textures and decals on raw meshes. We do all this without explicitly repairing the input, thereby avoiding the costly additional efforts. In order to enable broad applicability we provide details on two implementation variants, one optimized for performance, the other optimized for memory efficiency. Using the presented framework many applications can readily be extended to deal with imperfect meshes. Since we abstract from the input applicability is not even limited to meshes, other representations can be handled as well.
Learning Line Features in 3D Geometry
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Sunkel, Martin; Jansen, Silke; Wand, Michael; Eisemann, Elmar; Seidel, Hans-Peter; M. Chen and O. Deussen
Feature detection in geometric datasets is a fundamental tool for solving shape matching problems such as partial symmetry detection. Traditional techniques usually employ a priori models such as crease lines that are unspecific to the actual application. Our paper examines the idea of learning geometric features. We introduce a formal model for a class of linear feature constellations based on a Markov chain model and propose a novel, efficient algorithm for detecting a large number of features simultaneously. After a short user-guided training stage, in which one or a few example lines are sketched directly onto the input data, our algorithm automatically finds all pieces of geometry similar to the marked areas. In particular, the algorithm is able recognize larger classes of semantically similar but geometrically varying features, which is very difficult using unsupervised techniques. In a number of experiments, we apply our technique to point cloud data from 3D scanners. The algorithm is able to detect features with very low rates of false positives and negatives and to recognize broader classes of similar geometry (such as "windows" in a building scan) even from few training examples, thereby significantly improving over previous unsupervised techniques.
Dynamic Display of BRDFs
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Hullin, Matthias B.; Lensch, Hendrik P. A.; Raskar, Ramesh; Seidel, Hans-Peter; Ihrke, Ivo; M. Chen and O. Deussen
This paper deals with the challenge of physically displaying reflectance, i.e., the appearance of a surface and its variation with the observer position and the illuminating environment. This is commonly described by the bidirectional reflectance distribution function (BRDF). We provide a catalogue of criteria for the display of BRDFs, and sketch a few orthogonal approaches to solving the problem in an optically passive way. Our specific implementation is based on a liquid surface, on which we excite waves in order to achieve a varying degree of anisotropic roughness. The resulting probability density function of the surface normal is shown to follow a Gaussian distribution similar to most established BRDF models.
Component-wise Controllers for Structure-Preserving Shape Manipulation
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Zheng, Youyi; Fu, Hongbo; Cohen-Or, Daniel; Au, Oscar Kin-Chung; Tai, Chiew-Lan; M. Chen and O. Deussen
Recent shape editing techniques, especially for man-made models, have gradually shifted focus from maintaining local, low-level geometric features to preserving structural, high-level characteristics like symmetry and parallelism. Such new editing goals typically require a pre-processing shape analysis step to enable subsequent shape editing. Observing that most editing of shapes involves manipulating their constituent components, we introduce component-wise controllers that are adapted to the component characteristics inferred from shape analysis. The controllers capture the natural degrees of freedom of individual components and thus provide an intuitive user interface for editing. A typical model usually results in a moderate number of controllers, allowing easy establishment of semantic relations among them by automatic shape analysis supplemented with user interaction. We propose a component-wise propagation algorithm to automatically preserve the established inter-relations while maintaining the defining characteristics of individual controllers and respecting the user-specified modeling constraints. We extend these ideas to a hierarchical setup, allowing the user to adjust the tool complexity with respect to the desired modeling complexity. We demonstrate the effectiveness of our technique on a wide range of manmade models with structural features, often containing multiple connected pieces.
Paint Mesh Cutting
(The Eurographics Association and Blackwell Publishing Ltd., 2011) Fan, Lubin; Liu, Ligang; Liu, Kun; M. Chen and O. Deussen
We present a novel progressive painting-based mesh cut out tool, called Paint Mesh Cutting, for interactive mesh segmentation. Different from the previous user interfaces, the user only needs to draw a single stroke on the foreground region and then obtains the desired cutting part at an interactive rate. Moreover, the user progressively paints the region of interest using a brush and has the instant feedback on cutting results as he/she drags the mouse. This is achieved by efficient local graph-cut based optimizations based on the Gaussian mixture models (GMM) on the shape diameter function (SDF) metric of the shape. We demonstrate a number of various examples to illustrate the flexibility and applicability of our system and present a user study that supports the advantages of our user interface.

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