EG2013

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

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Modeling Terrains and Subsurface Geology
(The Eurographics Association, 2013) Natali, Mattia; Lidal, Endre M.; Parulek, Julius; Viola, Ivan; Patel, Daniel; M. Sbert and L. Szirmay-Kalos
The process of creating terrain and landscape models is important in a variety of computer graphics and visualization applications, from films and computer games, via flight simulators and landscape planning, to scientific visualization and subsurface modelling. Interestingly, the modelling techniques used in this large range of application areas have started to meet in the last years. In this state-of-the-art report, we present two taxonomies of different modelling methods. Firstly we present a data oriented taxonomy, where we divide modelling into three different scenarios: the data-free, the sparse-data and the dense-data scenario. Then we present a workflow oriented taxonomy, where we divide modelling into the separate stages necessary for creating a geological model. We start the report by showing that the new trends in geological modelling are approaching the modelling methods that have been developed in computer graphics. We then give an introduction to the process of geological modelling followed by our two taxonomies with descriptions and comparisons of selected methods. Finally we discuss the challenges and trends in geological modelling.
Scene Graph Creation And Management For Undergraduates
(The Eurographics Association, 2013) Jones, Matthew; Shesh, Amit; Jean-Jacques Bourdin and Eva Cerezo and Steve Cunningham
This paper describes the context and results of a student project related to scene graphs spanning several assignments in an undergraduate computer graphics course. The project progressively built an application that created a list of objects from an XML specification, modified it into a scene graph, implemented part-by-part animation and added point lights and textures. Students were encouraged to build creative models using implicit shapes. It was completed individually by 21 undergraduate students in three stages spanning 6-7 weeks. This project was further extended in the last two assignments by incorporating a ray tracer within it.
A Segmentation Transfer Method for Articulated Models
(The Eurographics Association, 2013) Elghoul, Esma; Verroust-Blondet, Anne; M.- A. Otaduy and O. Sorkine
In this paper, we propose using a pre-segmented example model to perform semantic-oriented segmentation of non-rigid 3D models of the same class (human, octopus, quadrupeds, etc.). Using the fact that the same type of non-rigid models share the same global topological structure, we exploit coarse topological shape attributes in conjunction with a seed-based segmentation approach to transfer a meaningful and consistent segmentation from the example to the target models. Promising results of inter-shape segmentation transfer are shown and discussed for different classes of models.
Real-Time Image-Based Volume Lighting
(The Eurographics Association, 2013) Delalandre, Cyril; Gautron, Pascal; Marvie, Jean-Eudes; M.- A. Otaduy and O. Sorkine
The interaction of translucent objects with light creates complex effects such as scattering, absorption and volumetric shadows. While most accurate rendering approaches resort to heavy computations, recent needs in interactive applications have led to new types of algorithms, trading quality or genericity for speed.
Real-time Control and Stopping of Fluids
(The Eurographics Association, 2013) Zsolnai, Károly; Szirmay-Kalos, László; Miguel Chover and A. Augusto de Sousa
In this paper we address the fluid control problem, where an arbitrary density distribution (a shape of any kind) is given, and forces are exerted to get the fluid to flow into this shape and stop when the target distribution is reached. We present a real-time solution.
Project-Based Learning of Advanced Computer Graphics and Interaction
(The Eurographics Association, 2013) Romero, Mario; Jean-Jacques Bourdin and Eva Cerezo and Steve Cunningham
This paper presents an educational case study and its pedagogical lessons. It is a project-based course in advanced computer graphics and interaction, DH2413, conducted in the fall of 2012 at the Royal Institute of Technology (KTH), Stockholm, Sweden. The students and the teacher, the author, learned through a constructivist approach. The students defined and researched the material covered in class through their theme selection of original research projects which consisted of interactive graphics systems. The students demonstrated, taught, and discussed with each other what they had learned. Finally, the students openly presented their work to hundreds of people in large public venues. The teacher s role was to design the learning environment, guide the research, provide indepth lectures on the research material chosen by the students, and organize and motivate the students to produce accountable results. In synthesis, the pedagogical lessons are: 1) learning means building with self-motivation, guidance, and accountability; 2) self-motivation means trust and independence; 3) guidance means asking for less, not more; and 4) accountability means public presentations of working systems.
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.
Transfinite Surface Patches Using Curved Ribbons
(The Eurographics Association, 2013) Várady, Tamás; Salvi, Péter; Rockwood, Alyn; M.- A. Otaduy and O. Sorkine
An important problem in Computer Aided Design is to create digital representations for complex free-form objects that produce nice, predictable shapes and facilitate real-time editing in 3D. The clue to curve network-based design is the construction of smoothly connected multi-sided patches. A new type of transfinite surface, called Composite Ribbon (CR) patch is introduced, that is a combination of curved ribbons and ensures G1 continuity over non-regular, convex polygonal domains. After discussing the construction and the preferred parameterization scheme, a few simple examples conclude the paper.
State of the Art of Parallel Coordinates
(The Eurographics Association, 2013) Heinrich, Julian; Weiskopf, Daniel; M. Sbert and L. Szirmay-Kalos
This work presents a survey of the current state of the art of visualization techniques for parallel coordinates. It covers geometric models for constructing parallel coordinates and reviews methods for creating and understanding visual representations of parallel coordinates. The classification of these methods is based on a taxonomy that was established from the literature and is aimed at guiding researchers to find existing techniques and identifying white spots that require further research. The techniques covered in this survey are further related to an established taxonomy of knowledge-discovery tasks to support users of parallel coordinates in choosing a technique for their problem at hand. Finally, we discuss the challenges in constructing and understanding parallel-coordinates plots and provide some examples from different application domains.
Graph Abstraction for Simplified Proofreading of Slice-based Volume Segmentation
(The Eurographics Association, 2013) Sicat, Ronell B.; Hadwiger, Markus; Mitra, Niloy J.; M.- A. Otaduy and O. Sorkine
Volume segmentation is an integral data analysis tool in experimental science. For example, in neuroscience, analysis of 3D volumes of neural structures from electron microscopy data is a key analysis step. Despite advances in computational methods, experts still prefer to manually proofread and correct the automatic segmentation outputs. Such corrections are often annotated at the level of data slices in order to minimize distortion artifacts and effectively handle the massive data volumes. In absence of crucial global context in 3D, such a workflow remains tedious, time consuming, and error prone. In this paper, we present a simple graph-based abstraction for segmentation volumes leading to an interactive proofreading tool making the process simpler, faster, and intuitive. Starting from an initial volume segmentation, we first construct a graph abstraction and then use it to identify potential problematic regions for the user to investigate and correct spurious segmentations, if identified. We also use the graph to suggest automatic corrections, thus drastically simplifying the proofreading effort. We implemented the proofreading tool as an Avizo c plugin and evaluated the method on complex real-world use cases.
Video Visualization
(The Eurographics Association, 2013) Borgo, Rita; Chen, Min; Höferlin, Markus; Kurzhals, Kuno; Legg, Phil; Walton, Simon; Weiskopf, Daniel; Diego Gutierrez and Karol Myszkowski
Video data, generated by the entertainment industry, security and traffic cameras, video conferencing systems, video emails, and so on, is particularly time-consuming to process by human beings. The field of visualization has provided this challenging problem with a collection of techniques that transform videos to different visual forms in order to reduce the time required to watch the video. In this tutorial, we will introduce the concept of video visualization, and several elementary techniques for processing and rendering a video into a compact visual representation. We will describe a family of visual representations, a set of insight obtained from empirical studies, and a collection of applications.
Poisson Image Analogy: Texture-Aware Seamless Cloning
(The Eurographics Association, 2013) Yoshizawa, Shin; Yokota, Hideo; Miguel Chover and A. Augusto de Sousa
Synthesizing two images with seamless boundaries, i.e. seamless image cloning, is important and has many useful applications in CG. Previous approaches do not produce realistic results if texture details of the two images are different.We propose a novel texture-aware seamless cloning framework based on separately processing the details and base image colors. The proposed framework provides realistic cloning results with seamless texture details.
Multi-Camera Acquisition and Placement Strategy for Displaying High-Resolution Images for Telepresence Systems
(The Eurographics Association, 2013) Islam, Tariqul; Ohl, Stephan; Staadt, Oliver; Miguel Chover and A. Augusto de Sousa
Life-size high-resolution telepresence systems, used for remote collaboration, face the problem of transmitting huge data from multiple viewpoints. We present different strategies focusing on efficient camera selection and acquisition method to discard part of image data for transmission as a preprocess to classical video compression schemes. At the the receiver site, part of the omitted data can be restored by means of super-resolution methods.
Seam-Driven Image Stitching
(The Eurographics Association, 2013) Gao, Junhong; Li, Yu; Chin, Tat-Jun; Brown, Michael S.; M.- A. Otaduy and O. Sorkine
Image stitching computes geometric transforms to align images based on the best fit of feature correspondences between overlapping images. Seam-cutting is used afterwards to to hide misalignment artifacts. Interestingly it is often the seam-cutting step that is the most crucial for obtaining a perceptually seamless result. This motivates us to propose a seam-driven image stitching strategy where instead of estimating a geometric transform based on the best fit of feature correspondences, we evaluate the goodness of a transform based on the resulting visual quality of the seam-cut. We show that this new image stitching strategy can often produce better perceptual results than existing methods especially for challenging scenes.
DCGI Laboratories at CTU Prague, Czech Republic
(The Eurographics Association, 2013) Bittner, Jiri; Zara, Jiri; J. C. Torres and A. Lecuyer
The Department of Computer Graphics and Interaction (DCGI) covers education and research activities in Computer Graphics and Human-Computer Interaction areas at the Czech Technical University in Prague (CTU). This paper presents the staff, laboratories, projects, and selected scientific achievements of the DCGI.
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.
Computational Fabrication and Display of Material Appearance
(The Eurographics Association, 2013) Hullin, Matthias B.; Ihrke, Ivo; Heidrich, Wolfgang; Weyrich, Tim; Damberg, Gerwin; Fuchs, Martin; M. Sbert and L. Szirmay-Kalos
After decades of research on digital representations of material and object appearance, computer graphics has more recently turned to the problem of creating physical artifacts with controllable appearance characteristics. While this work has mostly progressed in two parallel streams - display technologies as well as novel fabrication processes - we believe there is a large overlap and the potential for synergies between these two approaches. In this report, we summarize research efforts from the worlds of fabrication display, and categorize the different approaches into a common taxonomy. We believe that this report can serve as a basis for systematic exploration of the design space in future research.
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.
Size-Based Rendering for Lung Cancer Screening
(The Eurographics Association, 2013) Wiemker, Rafael; Bülow, Thomas; Klinder, Tobias; M.- A. Otaduy and O. Sorkine
We present two relevant clinical use cases for thoracic computed tomography data, where the recently introduced concept of size-based rendering can be beneficially applied to medical visualization in the context of screening for lung cancer and chronic obstructive pulmonary disease (COPD): (a) Gradual suppression of thorax and vessels for quick appraisal of the presence of pulmonary nodules. (b) Visualization of bullous versus diffuse emphysema. In the first use case, the opacity is chosen to decrease with local structure size, whereas in the second case, the opacity is chosen to increase with structure size. Both algorithms are robust in particular because they do not depend on any prior segmentation or classification. They are ideally suited for full parallelization and GPU implementation.
A Survey of Compressed GPU-Based Direct Volume Rendering
(The Eurographics Association, 2013) Rodríguez, Marcos Balsa; Gobbetti, Enrico; Guitián, José A. Iglesias; Makhinya, Maxim; Marton, Fabio; Pajarola, Renato; Suter, Susanne K.; M. Sbert and L. Szirmay-Kalos
Great advancements in commodity graphics hardware have favored GPU-based volume rendering as the main adopted solution for interactive exploration of rectilinear scalar volumes on commodity platforms. Nevertheless, long data transfer times and GPU memory size limitations are often the main limiting factors, especially for massive, time-varying or multi-volume visualization, or for networked visualization on the emerging mobile devices. To address this issue, a variety of level-of-detail data representations and compression techniques have been introduced. In order to improve capabilities and performance over the entire storage, distribution and rendering pipeline, the encoding/decoding process is typically highly asymmetric, and systems should ideally compress at data production time and decompress on demand at rendering time. Compression and level-of-detail pre-computation does not have to adhere to real-time constraints and can be performed off-line for high quality results. In contrast, adaptive real-time rendering from compressed representations requires fast, transient, and spatially independent decompression. In this report, we review the existing compressed GPU volume rendering approaches, covering compact representation models, compression techniques, GPU rendering architectures and fast decoding techniques.

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