EG2013

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

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Example-based Interpolation and Synthesis of Bidirectional Texture Functions
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Ruiters, Roland; Schwartz, Christopher; Klein, Reinhard; I. Navazo, P. Poulin
Bidirectional Texture Functions (BTF) have proven to be a well-suited representation for the reproduction of measured real-world surface appearance and provide a high degree of realism. We present an approach for designing novel materials by interpolating between several measured BTFs. For this purpose, we transfer concepts from existing texture interpolation methods to the much more complex case of material interpolation. We employ a separation of the BTF into a heightmap and a parallax compensated BTF to cope with problems induced by parallax, masking and shadowing within the material. By working only on the factorized representation of the parallax compensated BTF and the heightmap, it is possible to efficiently perform the material interpolation. By this novel method to mix existing BTFs, we are able to design plausible and realistic intermediate materials for a large range of different opaque material classes. Furthermore, it allows for the synthesis of tileable and seamless BTFs and finally even the generation of gradually changing materials following user specified material distribution maps.
Perceptually Motivated Real-Time Compression of Motion Data Enhanced by Incremental Encoding and Parameter Tuning
(The Eurographics Association, 2013) Firouzmanesh, Amirhossein; Cheng, Irene; Basu, Anup; M.- A. Otaduy and O. Sorkine
We address the problem of efficient real-time motion data compression considering human perception. Using incremental encoding plus a database of motion primitives for each key point, our method achieves a higher or competitive compression rate with less online overhead. Trade-off between visual quality and bandwidth usage can be tuned by varying a single threshold value. A user study was performed to measure the sensitivity of human subjects to reconstruction errors in key rotation angles. Based on these evaluations we are able to perform lossy compression on the motion data without noticeable degradation in rendered qualities. While achieving real-time performance, our technique outperforms other methods in our experiments by achieving a compression ratio exceeding 50 : 1 on regular sequences.
Effective Visual Exploration of Hemodynamics in Cerebral Aneurysms
(The Eurographics Association, 2013) Neugebauer, Mathias; Gasteiger, Rocco; Janiga, Gábor; Beuing, Oliver; Preim, Bernhard; Hans-Christian Hege and Anna Vilanova
Cerebral aneurysms are a pathological vessel dilatation that bear a high risk of rupture. For the understanding of this risk, the analysis of hemodynamic information plays an important role in clinical research. These information are obtained by computational fluid dynamics (CFD) simulations. Thus, an effective visual exploration of patient-specific blood flow behavior in cerebral aneurysms was developed to support the domain experts in their investigation process. We present advanced visualization and interaction techniques, which provide an overview, focus-and-context views as well as multi-level explorations. Moreover, an automatic extraction process of qualitative flow characteristics, which are correlated with the risk of rupture is introduced. Although not established in clinical routine yet, interviews and informal user studies confirm the usefulness of these methods.
Interactive Facades - Analysis and Synthesis of Semi-Regular Facades
(The Eurographics Association and Blackwell Publishing Ltd., 2013) AlHalawani, Sawsan; Yang, Yong-Liang; Liu, Han; Mitra, Niloy J.; I. Navazo, P. Poulin
Urban facades regularly contain interesting variations due to allowed deformations of repeated elements (e.g., windows in different open or close positions) posing challenges to state-of-the-art facade analysis algorithms. We propose a semi-automatic framework to recover both repetition patterns of the elements and their individual deformation parameters to produce a factored facade representation. Such a representation enables a range of applications including interactive facade images, improved multi-view stereo reconstruction, facade-level change detection, and novel image editing possibilities.
A Data-Driven Approach to Realistic Shape Morphing
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Gao, Lin; Lai, Yu-Kun; Huang, Qi-Xing; Hu, Shi-Min; I. Navazo, P. Poulin
Morphing between 3D objects is a fundamental technique in computer graphics. Traditional methods of shape morphing focus on establishing meaningful correspondences and finding smooth interpolation between shapes. Such methods however only take geometric information as input and thus cannot in general avoid producing unnatural interpolation, in particular for large-scale deformations. This paper proposes a novel data-driven approach for shape morphing. Given a database with various models belonging to the same category, we treat them as data samples in the plausible deformation space. These models are then clustered to form local shape spaces of plausible deformations. We use a simple metric to reasonably represent the closeness between pairs of models. Given source and target models, the morphing problem is casted as a global optimization problem of finding a minimal distance path within the local shape spaces connecting these models. Under the guidance of intermediate models in the path, an extended as-rigid-as-possible interpolation is used to produce the final morphing. By exploiting the knowledge of plausible models, our approach produces realistic morphing for challenging cases as demonstrated by various examples in the paper.
Using Webcams for Product Presentations in HTML5
(The Eurographics Association, 2013) Borg, Mathias; Kraus, Martin; Miguel Chover and A. Augusto de Sousa
The Media Capture and Streams API ("getUserMedia API") enables plug-in free webcam support in HTML5. This opens new ways of interacting with visualisations using open web standards. In this work, two techniques are proposed that employ the user's webcam for interactive product presentations on websites. The first technique tracks the user's face and uses its position to create the impression of a user-controlled rotation of a product by displaying a sequence of product images for different view points. The second technique uses photographs of a product with reflections of coloured patterns to render the user's webcam stream as a reflection in the product presentation. Thus, users in front of a webcam are able to see their virtual reflection in a picture of a real product in real time. Our implementation of two prototypes shows that it is technically possible to implement these features with HTML5 and JavaScript only.
Freeform Shadow Boundary Editing
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Mattausch, Oliver; Igarashi, Takeo; Wimmer, Michael; I. Navazo, P. Poulin
We present an algorithm for artistically modifying physically based shadows. With our tool, an artist can directly edit the shadow boundaries in the scene in an intuitive fashion similar to freeform curve editing. Our algorithm then makes these shadow edits consistent with respect to varying light directions and scene configurations, by creating a shadow mesh from the new silhouettes. The shadow mesh helps a modified shadow volume algorithm cast shadows that conform to the artistic shadow boundary edits, while providing plausible interaction with dynamic environments, including animation of both characters and light sources. Our algorithm provides significantly more fine-grained local and direct control than previous artistic light editing methods, which makes it simple to adjust the shadows in a scene to reach a particular effect, or to create interesting shadow shapes and shadow animations. All cases are handled with a single intuitive interface, be it soft shadows, or (self-)shadows on arbitrary receivers.
A Sensor Based Approach to Outdoor Illumination Estimation for Augmented Reality Applications on Mobile Devices
(The Eurographics Association, 2013) Barreira, João; Magalhães, Luís; Bessa, Maximino; Miguel Chover and A. Augusto de Sousa
Realistic Augmented Reality applications require integrating virtual objects in the real world in a seamless visual way. The main problem to obtain a perfect visual augmentation is rendering the virtual objects with consistent illumination. In this paper, we present a novel approach to estimate outdoor illumination for Augmented Reality applications on mobile devices based on information acquired from sensors. We use an ambient light sensor to automatically detect in real-time the scene illuminance, which is used to simulate the actual lighting conditions. As outdoor illumination is mostly dependent on the weather, we derived the sky/sun illumination parameters from the light sensor data based on the IESNA sky model. The sunlight direction is estimated based on information from the GPS, date and time of the day. The result is a practical solution for outdoor illumination estimation handling light changes under natural conditions and applying them to the rendering of virtual objects in the real scene.
Physics Storyboards
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Ha, Sehoon; McCann, Jim; Liu, C. Karen; Popovic, Jovan; I. Navazo, P. Poulin
Physical simulation and other procedural methods are increasingly popular tools in interactive applications because they generate complex and reactive behaviors given only a few parameter settings. This automation accelerates initial implementation, but also introduces a need to tune the available parameters until the desired behaviors emerge. These adjustments are typically performed iteratively, with the designer repeatedly running- and interacting with-the procedural animation with different parameter settings. Such a process is inaccurate, time consuming, and requires deep understanding and intuition, as parameters often have complex, nonlinear effects. Instead, we propose that designers construct physics storyboards to accelerate the process of tuning interactive, procedural animations. Physics storyboards are collections of space-time snapshots that highlight critical events and outcomes. They can be used to summarize the effects of parameter changes (without requiring the designer to perform extensive play-testing); and-when augmented with designer-provided evaluation functions-allow automatic parameter selection. We describe our implementation of this method, including how we use sampling to ensure that our automatically-selected parameters generalize, and how we time-warp user input to adapt it to changing parameters. We validate our implementation by using it to perform various design tasks in three example games.
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.
Smart Variations: Functional Substructures for Part Compatibility
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Zheng, Youyi; Cohen-Or, Daniel; Mitra, Niloy J.; I. Navazo, P. Poulin
As collections of 3D models continue to grow, reusing model parts allows generation of novel model variations. Naïvely swapping parts across models, however, leads to implausible results, especially when mixing parts across different model families. Hence, the user has to manually ensure that the final model remains functionally valid. We claim that certain symmetric functional arrangements (SFARR-s), which are special arrangements among symmetrically related substructures, bear close relation to object functions. Hence, we propose a purely geometric approach based on such substructures to match, replace, and position triplets of parts to create non-trivial, yet functionally plausible, model variations. We demonstrate that starting even from a small set of models such a simple geometric approach can produce a diverse set of non-trivial and plausible model variations.
Introductory Graphics for Very Diverse Audiences
(The Eurographics Association, 2013) Fairén, Marta; Pelechano, Nuria; Jean-Jacques Bourdin and Eva Cerezo and Steve Cunningham
This paper presents our first experience teaching WebGL in a master s degree for a class of students with very different backgrounds. The main challenge was to prepare a course that would be engaging for students with computer graphics experience, and yet interesting and non-frustrating for those students unfamiliar with OpenGL. In this paper we explain how we prepared this course, and the project assignment to achieve our goal. The results achieved by the students show that the course succeeded in keeping different kinds of students engaged and excited with the implementation of their final project.
Guided Capturing of Multi-view Stereo Datasets
(The Eurographics Association, 2013) Langguth, Fabian; Goesele, Michael; M.- A. Otaduy and O. Sorkine
We present an application for mobile devices, that allows any user, even without background in computer vision, to capture a complete set of images, that is suitable for a multi-view stereo reconstruction. Compared to related tasks, such as panorama capture, this setting is much harder, as the camera needs to move unrestricted in 3D space. Our system uses structure from motion to register captured images and generates a sparse reconstruction of the scene. The dataset is built in an incremental procedure, where the next best view is computed with a novel view planning strategy, that aims for a good coverage of the scene. The user is then guided towards the new view, and the image is captured automatically at the right position. The next iteration starts after the reconstruction has been updated. The quality of the resulting dataset is on par with datasets captured by an expert user.
Preface and Table of Contents
(The Eurographics Association and Blackwell Publishing Ltd., 2013) I. Navazo, P. Poulin
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.
Geosemantic Snapping for Sketch-Based Modeling
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Shtof, Alex; Agathos, Alexander; Gingold, Yotam; Shamir, Ariel; Cohen-Or, Daniel; I. Navazo, P. Poulin
Modeling 3D objects from sketches is a process that requires several challenging problems including segmentation, recognition and reconstruction. Some of these tasks are harder for humans and some are harder for the machine. At the core of the problem lies the need for semantic understanding of the shape's geometry from the sketch. In this paper we propose a method to model 3D objects from sketches by utilizing humans specifically for semantic tasks that are very simple for humans and extremely difficult for the machine, while utilizing the machine for tasks that are harder for humans. The user assists recognition and segmentation by choosing and placing specific geometric primitives on the relevant parts of the sketch. The machine first snaps the primitive to the sketch by fitting its projection to the sketch lines, and then improves the model globally by inferring geosemantic constraints that link the different parts. The fitting occurs in real-time, allowing the user to be only as precise as needed to have a good starting configuration for this non-convex optimization problem. We evaluate the accessibility of our approach with a user study.
OctaVis: A Virtual Reality System for Clinical Studies and Rehabilitation
(The Eurographics Association, 2013) Zell, Eduard; Dyck, Eugen; Kohsik, Agnes; Grewe, Philip; Flentge, David; Winter, York; Piefke, Martina; Botsch, Mario; Hans-Christian Hege and Anna Vilanova
Brain function disorders, resulting for instance from stroke, epilepsy, or other incidents can be partially recovered by rehabilitation training. Performing neuro-rehabilitation in virtual reality systems allows for training scenarios close to daily tasks, is easily adaptable to the patients' needs, is fully controllable by clinical staff, and guarantees patient safety at all times. In this paper, we describe the OCTAVIS system, a novel virtual reality platform developed primary for clinical studies with and rehabilitation training of patients with brain function disorders. To meet the special requirements for clinical use, our system has been designed with ease of use, ease of maintenance, patient safety, space and cost efficiency in mind. Our system has been successfully deployed to four hospitals, where it is used for rehabilitation training and clinical studies. We report first results of these studies, demonstrating that our system is immersive, easy to use, and supportive for rehabilitation purposes.
Fabrication-aware Design with Intersecting Planar Pieces
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Schwartzburg, Yuliy; Pauly, Mark; I. Navazo, P. Poulin
We propose a computational design approach to generate 3D models composed of interlocking planar pieces. We show how intricate 3D forms can be created by sliding the pieces into each other along straight slits, leading to a simple construction that does not require glue, screws, or other means of support. To facilitate the design process, we present an abstraction model that formalizes the main geometric constraints imposed by fabrication and assembly, and incorporates conditions on the rigidity of the resulting structure.We show that the tight coupling of constraints makes manual design highly nontrivial and introduce an optimization method to automate constraint satisfaction based on an analysis of the constraint relation graph. This algorithm ensures that the planar parts can be fabricated and assembled. We demonstrate the versatility of our approach by creating 3D toy models, an architectural design study, and several examples of functional furniture.
Stylized and Performative Gaze for Character Animation
(The Eurographics Association and Blackwell Publishing Ltd., 2013) Pejsa, Tomislav; Mutlu, Bilge; Gleicher, Michael; I. Navazo, P. Poulin
Existing models of gaze motion for character animation simulate human movements, incorporating anatomical, neurophysiological, and functional constraints. While these models enable the synthesis of humanlike gaze motion, they only do so in characters that conform to human anatomical proportions, causing undesirable artifacts such as cross-eyedness in characters with non-human or exaggerated human geometry. In this paper, we extend a state-of-the- art parametric model of human gaze motion with control parameters for specifying character geometry, gaze dynamics, and performative characteristics in order to create an enhanced model that supports gaze motion in characters with a wide range of geometric properties that is free of these artifacts. The model also affords ''staging effects'' by offering softer functional constraints and more control over the appearance of the character's gaze movements. An evaluation study showed that the model, compared with the state-of-the-art model, creates gaze motion with fewer artifacts in characters with non-human or exaggerated human geometry while retaining their naturalness and communicative accuracy.
Data-Driven Simulation Methods in Computer Graphics: Cloth, Tissue and Faces
(The Eurographics Association, 2013) Otaduy, Miguel A.; Bickel, Bernd; Bradley, Derek; Diego Gutierrez and Karol Myszkowski
In recent years, the field of computer animation has witnessed the invention of multiple simulation methods that exploit pre-recorded data to improve the performance and/or realism of dynamic deformations. Various methods have been presented concurrently, and they present differences, but also similarities, that have not yet been analyzed or discussed. This course focuses on the application of data-driven methods to three areas of computer animation, namely dynamic deformation of faces, soft volumetric tissue, and cloth. The course describes the particular challenges tackled in a data-driven manner, classifies the various methods, and also shares insights for the application to other settings. The explosion of data-driven animation methods and the success of their resultsmake this course extremely timely. Up till now, the proposed methods have remained familiar only at the research context, and have not made their way through computer graphics industry. This course aims to fit two main purposes. First, present a common theory and understanding of data-driven methods for dynamic deformations that may inspire the development of novel solutions, and second, bridge the gap with industry, by making data-driven approaches accessible. The course targets an audience consisting of both researchers and programmers in computer animation.

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