Search Results

Now showing 1 - 10 of 12
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    Pattern Search in Flows based on Similarity of Stream Line Segments
    (The Eurographics Association, 2014) Wang, Zhongjie; Esturo, Janick Martinez; Seidel, Hans-Peter; Weinkauf, Tino; Jan Bender and Arjan Kuijper and Tatiana von Landesberger and Holger Theisel and Philipp Urban
    We propose a method that allows users to define flow features in form of patterns represented as sparse sets of stream line segments. Our approach finds ''similar'' occurrences in the same or other time steps. Related approaches define patterns using dense, local stencils or support only single segments. Our patterns are defined sparsely and can have a significant extent, i.e., they are integration-based and not local. This allows for a greater flexibility in defining features of interest. Similarity is measured using intrinsic curve properties only, which enables invariance to location, orientation, and scale. Our method starts with splitting stream lines using globally-consistent segmentation criteria. It strives to maintain the visually apparent features of the flow as a collection of stream line segments. Most importantly, it provides similar segmentations for similar flow structures. For user-defined patterns of curve segments, our algorithm finds similar ones that are invariant to similarity transformations. We showcase the utility of our method using different 2D and 3D flow fields.
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    Interactive Motion Mapping for Real-time Character Control
    (The Eurographics Association and John Wiley and Sons Ltd., 2014) Rhodin, Helge; Tompkin, James; Kim, Kwang In; Varanasi, Kiran; Seidel, Hans-Peter; Theobalt, Christian; B. Levy and J. Kautz
    Abstract It is now possible to capture the 3D motion of the human body on consumer hardware and to puppet in real time skeleton-based virtual characters. However, many characters do not have humanoid skeletons. Characters such as spiders and caterpillars do not have boned skeletons at all, and these characters have very different shapes and motions. In general, character control under arbitrary shape and motion transformations is unsolved - how might these motions be mapped? We control characters with a method which avoids the rigging-skinning pipeline - source and target characters do not have skeletons or rigs. We use interactively-defined sparse pose correspondences to learn a mapping between arbitrary 3D point source sequences and mesh target sequences. Then, we puppet the target character in real time. We demonstrate the versatility of our method through results on diverse virtual characters with different input motion controllers. Our method provides a fast, flexible, and intuitive interface for arbitrary motion mapping which provides new ways to control characters for real-time animation.
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    Real-time Reflective and Refractive Novel-view Synthesis
    (The Eurographics Association, 2014) Lochmann, Gerrit; Reinert, Bernhard; Ritschel, Tobias; Müller, Stefan; Seidel, Hans-Peter; Jan Bender and Arjan Kuijper and Tatiana von Landesberger and Holger Theisel and Philipp Urban
    We extend novel-view image synthesis from the common diffuse and opaque image formation model to the reflective and refractive case. Our approach uses a ray tree of RGBZ images, where each node contains one RGB light path which is to be warped differently depending on the depth Z and the type of path. Core of our approach are two efficient procedures for reflective and refractive warping. Different from the diffuse and opaque case, no simple direct solution exists for general geometry. Instead, a per-pixel optimization in combination with informed initial guesses warps an HD image with reflections and refractions in 18 ms on a current mobile GPU. The key application is latency avoidance in remote rendering in particular for head-mounted displays. Other applications are single-pass stereo or multi-view, motion blur and depth-of-field rendering as well as their combinations.
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    Perceptually-motivated Stereoscopic Film Grain
    (The Eurographics Association and John Wiley and Sons Ltd., 2014) Templin, Krzysztof; Didyk, Piotr; Myszkowski, Karol; Seidel, Hans-Peter; J. Keyser, Y. J. Kim, and P. Wonka
    Independent management of film grain in each view of a stereoscopic video can lead to visual discomfort. The existing alternative is to project the grain onto the scene geometry. Such grain, however, looks unnatural, changes object perception, and emphasizes inaccuracies in depth arising during 2D-to-3D conversion. We propose an advanced method of grain positioning that scatters the grain in the scene space. In a series of perceptual experiments, we estimate the optimal parameter values for the proposed method, analyze the user preference distribution among the proposed and the two existing methods, and show influence of the method on the object perception.
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    Manipulating Refractive and Reflective Binocular Disparity
    (The Eurographics Association and John Wiley and Sons Ltd., 2014) Dabala, Lukasz; Kellnhofer, Petr; Ritschel, Tobias; Didyk, Piotr; Templin, Krzysztof; Myszkowski, Karol; Rokita, P.; Seidel, Hans-Peter; B. Levy and J. Kautz
    Presenting stereoscopic content on 3D displays is a challenging task, usually requiring manual adjustments. A number of techniques have been developed to aid this process, but they account for binocular disparity of surfaces that are diffuse and opaque only. However, combinations of transparent as well as specular materials are common in the real and virtual worlds, and pose a significant problem. For example, excessive disparities can be created which cannot be fused by the observer. Also, multiple stereo interpretations become possible, e. g., for glass, that both reflects and refracts, which may confuse the observer and result in poor 3D experience. In this work, we propose an efficient method for analyzing and controlling disparities in computer-generated images of such scenes where surface positions and a layer decomposition are available. Instead of assuming a single per-pixel disparity value, we estimate all possibly perceived disparities at each image location. Based on this representation, we define an optimization to find the best per-pixel camera parameters, assuring that all disparities can be easily fused by a human. A preliminary perceptual study indicates, that our approach combines comfortable viewing with realistic depiction of typical specular scenes.
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    Spectral Ray Differentials
    (The Eurographics Association and John Wiley and Sons Ltd., 2014) Elek, Oskar; Bauszat, Pablo; Ritschel, Tobias; Magnor, Marcus; Seidel, Hans-Peter; Wojciech Jarosz and Pieter Peers
    Light refracted by a dispersive interface leads to beautifully colored patterns that can be rendered faithfully with spectral Monte-Carlo methods. Regrettably, results often suffer from chromatic noise or banding, requiring high sampling rates and large amounts of memory compared to renderers operating in some trichromatic color space. Addressing this issue, we introduce spectral ray differentials, which describe the change of light direction with respect to changes in the spectrum. In analogy with the classic ray and photon differentials, this information can be used for filtering in the spectral domain. Effectiveness of our approach is demonstrated by filtering for offline spectral light and path tracing as well as for an interactive GPU photon mapper based on splatting. Our results show considerably less chromatic noise and spatial aliasing while retaining good visual similarity to reference solutions with negligible overhead in the order of milliseconds.
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    Sky Based Light Metering for High Dynamic Range Images
    (The Eurographics Association and John Wiley and Sons Ltd., 2014) Gryaditskya, Yulia; Pouli, Tania; Reinhard, Erik; Seidel, Hans-Peter; J. Keyser, Y. J. Kim, and P. Wonka
    Image calibration requires both linearization of pixel values and scaling so that values in the image correspond to real-world luminances. In this paper we focus on the latter and rather than rely on camera characterization, we calibrate images by analysing their content and metadata, obviating the need for expensive measuring devices or modeling of lens and camera combinations. Our analysis correlates sky pixel values to luminances that would be expected based on geographical metadata. Combined with high dynamic range (HDR) imaging, which gives us linear pixel data, our algorithm allows us to find absolute luminance values for each pixel-effectively turning digital cameras into absolute light meters. To validate our algorithm we have collected and annotated a calibrated set of HDR images and compared our estimation with several other approaches, showing that our approach is able to more accurately recover absolute luminance. We discuss various applications and demonstrate the utility of our method in the context of calibrated color appearance reproduction and lighting design.
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    Deep Screen Space for Indirect Lighting of Volumes
    (The Eurographics Association, 2014) Nalbach, Oliver; Ritschel, Tobias; Seidel, Hans-Peter; Jan Bender and Arjan Kuijper and Tatiana von Landesberger and Holger Theisel and Philipp Urban
    We present a method to render approximate indirect light transport from surfaces to volumes which is fully dynamic with respect to geometry, the medium and the main light sources, running at interactive speed. This is achieved in a three-step procedure. First, the scene is turned into a view-dependent level-of-detail surfel cloud using fast hardware tessellation. These surfels are lit and represent the senders of indirect light. Second, the current view of the volume is converted into a transmittance interval map, containing depth intervals in which the transmittance to the camera is reduced by the same fraction of the total extinction. These intervals will receive indirect illumination. Finally, surfels and intervals are linked by splatting the effect of the surfels into a hierarchical framebuffer. This linking delivers high precision between surfel-interval pairs that exchange much light and is coarser for pairs exchanging little, without constructing any explicit hierarchical data structure.
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    Progressive Spectral Ray Differentials
    (The Eurographics Association, 2014) Elek, Oskar; Bauszat, Pablo; Ritschel, Tobias; Magnor, Marcus; Seidel, Hans-Peter; Jan Bender and Arjan Kuijper and Tatiana von Landesberger and Holger Theisel and Philipp Urban
    Light travelling though refractive objects can lead to beautiful colourful illumination patterns resulting from dispersion on the object interfaces. While this can be accurately simulated by stochastic Monte-Carlo methods, their application is costly and leads to significant chromatic noise. This is greatly improved by applying spectral ray differentials, however, at the cost of introducing bias into the solution. We propose progressive spectral ray differentials, adapting concepts from other progressive Monte-Carlo methods. Our approach takes full advantage of the variance-reduction properties of spectral ray differentials but progressively converges to the correct, unbiased solution in the limit.
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    Sets of Globally Optimal Stream Surfaces for Flow Visualization
    (The Eurographics Association and John Wiley and Sons Ltd., 2014) Schulze, Maik; Esturo, Janick Martinez; Günther, Tobias; Rössl, Christian; Seidel, Hans-Peter; Weinkauf, Tino; Theisel, Holger; H. Carr, P. Rheingans, and H. Schumann
    Stream surfaces are a well-studied and widely used tool for the visualization of 3D flow fields. Usually, stream surface seeding is carried out manually in time-consuming trial and error procedures. Only recently automatic selection methods were proposed. Local methods support the selection of a set of stream surfaces, but, contrary to global selection methods, they evaluate only the quality of the seeding lines but not the quality of the whole stream surfaces. Global methods, on the other hand, only support the selection of a single optimal stream surface until now. However, for certain flow fields a single stream surface is not sufficient to represent all flow features. In our work, we overcome this limitation by introducing a global selection technique for a set of stream surfaces. All selected surfaces optimize global stream surface quality measures and are guaranteed to be mutually distant, such that they can convey different flow features. Our approach is an efficient extension of the most recent global selection method for single stream surfaces. We illustrate its effectiveness on a number of analytical and simulated flow fields and analyze the quality of the results in a user study.