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Item 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. RitschelVirtual 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.Item Interactive HDR Environment Map Capturing on Mobile Devices(The Eurographics Association, 2015) Kán, Peter; B. Bickel and T. RitschelReal 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.Item Sketch-Based Controllers for Blendshape Facial Animation(The Eurographics Association, 2015) Cetinaslan, Ozan; Orvalho, Verónica; Lewis, John; B. Bickel and T. RitschelThe 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.Item 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. RitschelSynthetic 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 explosionsItem Individual Time Stepping for SPH Fluids(The Eurographics Association, 2015) He, Liangliang; Ban, Xiaojuan; Liu, Xu; Wang, Xiaokun; B. Bickel and T. RitschelWe present a novel adaptive stepping scheme for SPH fluids, in which particles have their own time-steps determined from local conditions, e.g. Courant condition. These individual time-steps are constrained for global convergence and stability. Fluid particles are then updated asynchronously. The approach naturally allocates computing resources to visually complex regions, e.g. regions with intense collisions, thereby reducing the overall computational time. The experiments show that our approach is more efficient than the standard method and the method with globally adaptive time steps, especially in highly dynamic scenes.Item Improving k-buffer Methods via Occupancy Maps(The Eurographics Association, 2015) Vasilakis, Andreas A.; Papaioannou, Georgios; B. Bickel and T. RitschelIn this work, we investigate an efficient approach to treat fragment racing when computing k-nearest fragments. Based on the observation that knowing the depth position of the k-th fragment we can optimally find the k-closest fragments, we introduce a novel fragment culling component by employing occupancy maps.Without any softwareredesign, the proposed scheme can easily be attached at any k-buffer pipeline to efficiently perform early-z culling. Finally, we report on the efficiency, memory space, and robustness of the upgraded k-buffer alternatives providing comprehensive comparison results.Item Adaptive LightSlice for Virtual Ray Lights(The Eurographics Association, 2015) Frederickx, Roald; Bartels, Pieterjan; Dutré, Philip; B. Bickel and T. RitschelWe speed up the rendering of participating media with Virtual Ray Lights (VRLs) by clustering them in a preprocessing step. A subset of representative VRLs is then sampled from the clustering, which is used for the final rendering. By performing a full variance analysis, we can explicitly estimate the convergence rate of the rendering process and automatically find the locally ideal number of clusters to maximize efficiency. Overall, we report speed-up factors ranging from 13 to 16 compared to unclustered rendering.Item High-Quality Shadows for Streaming Terrain Rendering(The Eurographics Association, 2015) Chajdas, Matthäus G.; Reichl, Florian; Dick, Christian; Westermann, Rüdiger; B. Bickel and T. RitschelRendering of large, detailed 3D terrains on commodity hardware has become possible through the use of raycasting, data caching and prefetching. Adding dynamic shadows as they appear during a day-night cycle remais a challenge however, because shadow rendering requires access to the entire terrain, invalidating data streaming strategies. In this work we present a novel, practicable shadow rendering approach which distinguishes between near- and precomputed far-shadows to significantly reduce data access and runtime costs. While near-shadows are raytraced using the current cache content, far-shadows are precomputed and stored in a very compact format requiring approximately 3 bit per height-map sample for an entire day-night cycle.