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    Separation of Manga Line Drawings and Screentones
    (The Eurographics Association, 2015) Ito, Kota; Matsui, Yusuke; Yamasaki, Toshihiko; Aizawa, Kiyoharu; B. Bickel and T. Ritschel
    Screentones are unique expressions of Japanese comics (manga), which enrich their visual expression. However, such screentones have a very different visual nature from that of line drawing areas; this prevents us from applying various kinds of image processing techniques to manga. We propose a method for extracting line drawings and removing screentones. We employ Laplacians of Gaussian filters and flow-based differences of Gaussian filters, one for removing screentones and the other for preserving lines, and make a binary mask for separating line drawings from manga by merging the results of the two filters. We show that the proposed method successfully separates line drawings and is better than existing methods in comparative studies.
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    Eye-tracktive: Measuring Attention to Body Parts when Judging Human Motions
    (The Eurographics Association, 2015) Ennis, Cathy; Hoyet, Ludovic; O'Sullivan, Carol; B. Bickel and T. Ritschel
    Virtual humans are often endowed with human-like characteristics to make them more appealing and engaging. Motion capture is a reliable way to represent natural motion on such characters, thereby allowing a wide range of animations to be automatically created and replicated. However, interpersonal differences in actors' performances can be subtle and complex, yet have a strong effect on the human observer. Such effects can be very difficult to express quantitatively or indeed even qualitatively. We investigate two subjective human motion characteristics: attractiveness and distinctiveness. We conduct a perceptual experiment, where participants' eye movements are tracked while they rate the motions of a range of actors. We found that participants fixate mostly on the torso, regardless of gait and actor sex, and very little on the limbs. However, they self-reported that they used hands, elbows and feet in their judgments, indicating a holistic approach to the problem.
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    Isogeometric Analysis for Modelling and Design
    (The Eurographics Association, 2015) Riffnaller-Schiefer, Andreas; Augsdörfer, Ursula H.; Fellner, Dieter W.; B. Bickel and T. Ritschel
    We present an isogeometric design and analysis approach based on NURBS-compatible subdivision surfaces. The approach enables the description of watertight free-form surfaces of arbitrary degree, including conic sections and an accurate simulation and analysis based directly on the designed surface. To explore the seamless integration of design and analysis provided by the isogeometric approach, we built a prototype software which combines free-form modelling tools with thin shell simulation tools to offer the designer a wide range of design and analysis instruments.
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    EUROGRAPHICS 2015: Short Papers Frontmatter
    (Eurographics Association, 2015) Bernd Bickel; Tobias Ritschel;
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    Interactive HDR Environment Map Capturing on Mobile Devices
    (The Eurographics Association, 2015) Kán, Peter; B. Bickel and T. Ritschel
    Real world illumination, captured by digitizing devices, is beneficial to solve many problems in computer graphics. Therefore, practical methods for capturing this illumination are of high interest. In this paper, we present a novel method for capturing environmental illumination by a mobile device. Our method is highly practical as it requires only a consumer mobile phone and the result can be instantly used for rendering or material estimation.We capture the real light in high dynamic range (HDR) to preserve its high contrast. Our method utilizes the moving camera of a mobile phone in auto-exposure mode to reconstruct HDR values. The projection of the image to the spherical environment map is based on the orientation of the mobile device. Both HDR reconstruction and projection run on the mobile GPU to enable interactivity. Moreover, an additional image alignment step is performed. Our results show that the presented method faithfully captures the real environment and that the rendering with our reconstructed environment maps achieves high quality, comparable to reality.
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    3D Architectural Modeling: Efficient RANSAC for n-gonal Primitive Fitting
    (The Eurographics Association, 2015) Abdullah, Ahsan; Bajwa, Reema; Gilani, Syed Rizwan; Agha, Zuha; Boor, Saeed Boor; Taj, Murtaza; Khan, Sohaib Ahmed; B. Bickel and T. Ritschel
    We present a modeling approach to automatically fit 3D primitives to point clouds in order to generate a CAD like model. For detailed modeling we propose a new n-gonal 3D primitive and a novel RANSAC based fitting approach. Non-planar surfaces are modeled through surface of revolution with B-spline profiles. We first reduce the dimension by projecting the 3D data onto a 2D plane. Primitive fitting algorithm is then applied in this 2D space. Our approach compares favorably both with manually and automatically generated models. Not only is it much more time efficient than manual modeling, but it also gives significantly better output than state-of-the-art automatic methods. Since the focal technique of our approach is the fitting of detailed primitives, our results are ideal in the domain of architecture and preservation of heritage.
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    Fast Edge-based Geodesic Poisson Disk Remeshing
    (The Eurographics Association, 2015) Uhlmann, Tom; Váša, Libor; Brunnett, Guido; B. Bickel and T. Ritschel
    Triangular meshes of high complexity are common when created by a 3D scanner device and must be reduced for further processing. The geodesic Poisson disk remeshing [FZ08] is a method that generates a simplified mesh with highly regular triangles at the cost of exorbitant computation time. In this paper we will outline a new approach to this technique that makes it applicable for highly complex models. Our approach operates directly on the surface of the mesh, therefore works for meshes of arbitrary topology. Meshes consisting of millions of triangles can be reduced to an arbitrary complexity in just a few minutes while the original approach processes meshes with thousands of triangles in the same time. Our easy to implement remeshing technique also provides several options to preserve features.
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    Sketch-Based Controllers for Blendshape Facial Animation
    (The Eurographics Association, 2015) Cetinaslan, Ozan; Orvalho, Verónica; Lewis, John; B. Bickel and T. Ritschel
    The blendshape approach is a widely used technique to generate realistic facial animation. However, creating blendshape facial animations using traditional weight editing tools requires either memorizing the function of a large number of parameters, or a trial-and-error search in a high-dimensional space. Direct manipulation interfaces address this problem, allowing the artist to directly move and pin manipulators placed on the surface of the face. Placing manipulators is an open-ended and slightly unnatural task for artists however. In this paper we present a sketch-based approach to this problem, inspired by artists' brush painting on canvas. In this approach the artist simply sketches directly onto the 3D model the positions of the manipulators that they feel are needed to produce particular facial expression. The manipulators activate the blendshapes in the model and allow the user to interactively create the desired facial poses by a dragging operation in screen coordinates. Our hybrid method can be used with any blendshape facial model and allows producing expeditious manipulation in an intuitive way.
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    Interactive Pixel-Accurate Rendering of LR-Splines and T-Splines
    (The Eurographics Association, 2015) Hjelmervik, Jon M.; Fuchs, Franz G.; B. Bickel and T. Ritschel
    Flexible surface types on irregular grids, such as T-splines and LR-splines, are gaining popularity in science and industry due to the possibility for local grid refinement. We present a novel rendering algorithm for those surface types that guarantees pixel-accurate geometry and water-tight tessellation (no drop-outs). Before rendering, we extract the Bézier coefficients. The resulting irregular grids of Bézier patches are then rendered using a multistage algorithm, that decouples the tesselator and the patch geometry. The implementation using OpenGL utilizes compute shaders and hardware tessellation functionality. We showcase interactive rendering achieved by our approach on three representative use cases.
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    An Interactive Editing System for Visual Appearances of Fire and Explosions
    (The Eurographics Association, 2015) Dobashi, Yoshinori; Shibukawa, Yuhei; Tada, Munehiro; Sato, Syuhei; Iwasaki, Kei; Yamamoto, Tsuyoshi; B. Bickel and T. Ritschel
    Synthetic volumetric fire and explosions are important visual effects used in many applications such as computer games and movies. For these applications, artists are often requested to achieve the desired visual appearance by adjusting some parameters for rendering them. However, this is extremely difficult and tedious, due to the complexity of these phenomena and the expensive computational cost for the rendering. This paper presents an interactive system that assists this adjustment process. Our method allows the user to interactively change the ratio of smoke and flame regions, the emissivity of the flame, and the optical thicknesses of the smoke and flame separately. The image is updated in real-time while the user modifies these parameters, taking into account the multiple scattering of light. We demonstrate the usefulness of our method by applying our method to editing of the visual appearances of fire and explosions