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Item Microtiles: Extracting Building Blocks from Correspondences(The Eurographics Association and Blackwell Publishing Ltd., 2012) Kalojanov, Javor; Bokeloh, Martin; Wand, Michael; Guibas, Leonidas; Seidel, Hans-Peter; Slusallek, Philipp; Eitan Grinspun and Niloy MitraIn this paper, we develop a theoretical framework for characterizing shapes by building blocks. We address two questions: First, how do shape correspondences induce building blocks? For this, we introduce a new representation for structuring partial symmetries (partial self-correspondences), which we call "microtiles". Starting from input correspondences that form point-wise equivalence relations, microtiles are obtained by grouping connected components of points that share the same set of symmetry transformations. The decomposition is unique, requires no parameters beyond the input correspondences, and encodes the partial symmetries of all subsets of the input. The second question is: What is the class of shapes that can be assembled from these building blocks? Here, we specifically consider r-similarity as correspondence model, i.e., matching of local r-neighborhoods. Our main result is that the microtiles of the partial r-symmetries of an object S can build all objects that are (r+e)-similar to S for any e>0. Again, the construction is unique. Furthermore, we give necessary conditions for a set of assembly rules for the pairwise connection of tiles. We describe a practical algorithm for computing microtile decompositions under rigid motions, a corresponding prototype implementation, and conduct a number of experiments to visualize the structural properties in practice.Item Optimizing Disparity for Motion in Depth(The Eurographics Association and Blackwell Publishing Ltd., 2013) Kellnhofer, Petr; Ritschel, Tobias; Myszkowski, Karol; Seidel, Hans-Peter; Nicolas Holzschuch and Szymon RusinkiewiczBeyond the careful design of stereo acquisition equipment and rendering algorithms, disparity post-processing has recently received much attention, where one of the key tasks is to compress the originally large disparity range to avoid viewing discomfort. The perception of dynamic stereo content however, relies on reproducing the full disparity-time volume that a scene point undergoes in motion. This volume can be strongly distorted in manipulation, which is only concerned with changing disparity at one instant in time, even if the temporal coherence of that change is maintained. We propose an optimization to preserve stereo motion of content that was subject to an arbitrary disparity manipulation, based on a perceptual model of temporal disparity changes. Furthermore, we introduce a novel 3D warping technique to create stereo image pairs that conform to this optimized disparity map. The paper concludes with perceptual studies of motion reproduction quality and task performance in a simple game, showing how our optimization can achieve both viewing comfort and faithful stereo motion.Item Lightness Perception in Tone Reproduction for High Dynamic Range Images(The Eurographics Association and Blackwell Publishing, Inc, 2005) Krawczyk, Grzegorz; Myszkowski, Karol; Seidel, Hans-PeterItem Harmonic Guidance for Surface Deformation(The Eurographics Association and Blackwell Publishing, Inc, 2005) Zayer, Rhaleb; Roessl, Christian; Karni, Zachi; Seidel, Hans-PeterItem Efficient Rendering of Local Subsurface Scattering(The Eurographics Association and Blackwell Publishing Ltd., 2005) Mertens, Tom; Kautz, Jan; Bekaert, Philippe; Van Reeth, Frank; Seidel, Hans-PeterA novel approach is presented to efficiently render local subsurface scattering effects. We introduce an importance sampling scheme for a practical subsurface scattering model. It leads to a simple and efficient rendering algorithm, which operates in image space, and which is even amenable for implementation on graphics hardware. We demonstrate the applicability of our technique to the problem of skin rendering, for which the subsurface transport of light typically remains local. Our implementation shows that plausible images can be rendered interactively using hardware acceleration.Item Fast Final Gathering via Reverse Photon Mapping(The Eurographics Association and Blackwell Publishing, Inc, 2005) Havran, Vlastimil; Herzog, Robert; Seidel, Hans-PeterItem Using Procedural RenderMan Shaders for Global Illurnination(Blackwell Science Ltd and the Eurographics Association, 1995) Slusallek, Philipp; Pflaum, Thomas; Seidel, Hans-PeterGlobal illumination techniques like radiosity or Monte-Carlo ray-tracing are becoming standard features of rendering systems. However, there is currently no accepted interface format which supports an appropriate physically-based scene description. In this paper we present extensions to the well-known RenderMan interface, which allow for a physically based scene description and support advanced global illumination techniques. Special emphasis has been laid on the support for procedural descriptions of reflection and emission by RenderMan surface shaders. So far, they could not be used with most global illumination algorithms. The extensions have been implemented in a physically-based rendering system and are illustrated with examples.Item Editing Object Behaviour in Video Sequences(The Eurographics Association and Blackwell Publishing Ltd, 2009) Scholz, Volker; El-Abed, Sascha; Seidel, Hans-Peter; Magnor, MarcusWhile there are various commercial-strength editing tools available today for still images, object-based manipulation of real-world video footage is still a challenging problem. In this system paper, we present a framework for interactive video editing. Our focus is on footage from a single, conventional video camera. By relying on spatio-temporal editing techniques operating on the video cube, we do not need to recover 3D scene geometry. Our framework is capable of removing and inserting objects, object motion editing, non-rigid object deformations, keyframe interpolation, as well as emulating camera motion. We demonstrate how movie shots with moderate complexity can be persuasively modified during post-processing.Item 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. KautzAbstract 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.Item Measurement-Based Interactive Simulation of Viscoelastic Solids(The Eurographics Association and Blackwell Publishing, Inc, 2004) Schoner, Jeffrey L.; Lang, Jochen; Seidel, Hans-PeterAnimation of viscoelastic solids in entertainment and medical applications as well as scientific simulation can be improved through observations of real world objects. This paper presents a method for simulating viscoelastic solids in real-time for visual and haptic display along with a method for determining the parameters of the the underlying model from automated physical measurements of real world objects. The viscoelastic model is a novel extension of the discrete Green's function matrix for linear elasticity, which combines static behavior represented by Green's functions with dynamic behavior expressed by differential equations inspired by particle systems. We describe a novel estimation method of dynamic contact behavior for heterogeneous complex objects based on these measurements. For this estimation, our method relies only on measurement data previously used in the acquisition less realistic elastostatic models. In this way our method allows more physically accurate realism in animation of viscoelastic solids without large additional computational costs or any measurements besides those associated with related methods for elastostatic solids.Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Physically based modeling I.3.7 [Computer Graphics]: Virtual reality, animation