DSpace Repository

Search Results

Now showing 1 - 10 of 134

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 Mitra
In 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.
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 Rusinkiewicz
Beyond 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.
Lightness Perception in Tone Reproduction for High Dynamic Range Images
(The Eurographics Association and Blackwell Publishing, Inc, 2005) Krawczyk, Grzegorz; Myszkowski, Karol; Seidel, Hans-Peter
Efficient and Robust Annotation of Motion Capture Data
(ACM SIGGRAPH / Eurographics Association, 2009) Müller, Meinard; Baak, Andreas; Seidel, Hans-Peter; Eitan Grinspun and Jessica Hodgins
In view of increasing collections of available 3D motion capture (mocap) data, the task of automatically annotating large sets of unstructured motion data is gaining in importance. In this paper, we present an efficient approach to label mocap data according to a given set of motion categories or classes, each specified by a suitable set of positive example motions. For each class, we derive a motion template that captures the consistent and variable aspects of a motion class in an explicit matrix representation. We then present a novel annotation procedure, where the unknown motion data is segmented and annotated by locally comparing it with the available motion templates. This procedure is supported by an efficient keyframe-based preprocessing step, which also significantly improves the annotation quality by eliminating false positive matches. As a further contribution, we introduce a genetic learning algorithm to automatically learn the necessary keyframes from the given example motions. For evaluation, we report on various experiments conducted on two freely available sets of motion capture data (CMU and HDM05).
Real-Time Bump Map Synthesis
(The Eurographics Association, 2001) Kautz, Jan; Heidrich, Wolfgang; Seidel, Hans-Peter; Kurt Akeley and Ulrich Neumann
In this paper we present a method that automatically synthesizes bump maps at arbitrary levels of detail in real-time. The only input data we require is a normal density function; the bump map is generated according to that function. It is also used to shade the generated bump map. The technique allows to infinitely zoom into the surface, because more (consistent) detail can be created on the fly. The shading of such a surface is consistent when displayed at different distances to the viewer (assuming that the surface structure is self-similar). The bump map generation and the shading algorithm can also be used separately.
Bayesian Relighting
(The Eurographics Association, 2005) Fuchs, Martin; Blanz, Volker; Seidel, Hans-Peter; Kavita Bala and Philip Dutre
We present a simple method for relighting real objects viewed from a fixed camera position. Instead of setting up a calibrated measurement device, such as a light stage, we manually sweep a spotlight over the walls of a white room, illuminating the object indirectly. In contrast to previous methods, we use arbitrary and unknown angular distributions of incoming light. Neither the incident light nor the reflectance function need to be represented explicitly in our approach. The new method relies on images of a probe object, for instance a black snooker ball, placed near the target object. Pictures of the probe in a novel illumination are decomposed into a linear combination of measured images of the probe. Then, a linear combination of images of the target object with the same coefficients produces a synthetic image with the new illumination. We use a simple Bayesian approach to find the most plausible output image, given the picture of the probe and the statistics observed in the dataset of samples. Our results for a variety of novel illuminations, including synthetic lighting by relatively narrow light sources as well as natural illuminations, demonstrate that the new technique is a useful, low cost alternative to existing techniques for a broad range of objects and materials.
Robust Filtering of Noisy Scattered Point Data
(The Eurographics Association, 2005) Schall, Oliver; Belyaev, Alexander; Seidel, Hans-Peter; Marc Alexa and Szymon Rusinkiewicz and Mark Pauly and Matthias Zwicker
In this paper, we develop a method for robust filtering of a noisy set of points sampled from a smooth surface. The main idea of the method consists of using a kernel density estimation technique for point clustering. Specifically, we use a mean-shift based clustering procedure. With every point of the input data we associate a local likelihood measure capturing the probability that a 3D point is located on the sampled surface. The likelihood measure takes into account the normal directions estimated at the scattered points. Our filtering procedure suppresses noise of different amplitudes and allows for an easy detection of outliers which are then automatically removed by simple thresholding. The remaining set of maximum likelihood points delivers an accurate point-based approximation of the surface. We also show that while some established meshing techniques often fail to reconstruct the surface from original noisy point scattered data, they work well in conjunction with our filtering method.
Harmonic Guidance for Surface Deformation
(The Eurographics Association and Blackwell Publishing, Inc, 2005) Zayer, Rhaleb; Roessl, Christian; Karni, Zachi; Seidel, Hans-Peter
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-Peter
A 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.
Fast Final Gathering via Reverse Photon Mapping
(The Eurographics Association and Blackwell Publishing, Inc, 2005) Havran, Vlastimil; Herzog, Robert; Seidel, Hans-Peter

Filters

Author

Subject

Date

Has files

Settings

Sort By

Results per page

Search Results