21 results
Search Results
Now showing 1 - 10 of 21
Item Online Adaptive PCA for Inverse Kinematics Hand Tracking(The Eurographics Association, 2014) Schröder, Matthias; Botsch, Mario; Jan Bender and Arjan Kuijper and Tatiana von Landesberger and Holger Theisel and Philipp UrbanRecent approaches to real-time bare hand tracking estimate the hand's pose and posture by fitting a virtual hand model to RGBD sensor data using inverse kinematics. It has been shown that exploiting natural hand synergies can improve the efficiency and quality of the tracking, by performing the optimization in a reduced parameter space consisting of realistic hand postures [SMRB14]. The downside, however, is that only postures within this subspace can be tracked reliably, thereby trading off flexibility and accuracy for performance and robustness. In this paper we extend the previous method by introducing an adaptive synergistic model that is automatically adjusted to observed hand articulations that are not covered by the initial subspace. Our adaptive model combines the robustness of tracking in a reduced parameter space with the flexibility of optimizing for the full articulation of the hand, which we demonstrate in several synthetic and real-world experiments.Item Evaluation of Surround-View and Self-Rotation in the OCTAVIS VR-System(The Eurographics Association, 2013) Dyck, Eugen; Pfeiffer, Thies; Botsch, Mario; Betty Mohler and Bruno Raffin and Hideo Saito and Oliver StaadtIn this paper we evaluate spatial presence and orientation in the OCTAVIS system, a novel virtual reality platform aimed at training and rehabilitation of visual-spatial cognitive abilities. It consists of eight touch-screen displays surrounding the user, thereby providing a 360! horizontal panorama view. A rotating office chair and a joystick in the armrest serve as input devices to easily navigate through the virtual environment. We conducted a two-step experiment to investigate spatial orientation capabilities with our device. First, we examined whether the extension of the horizontal field of view from 135! (three displays) to 360! (eight displays) has an effect on spatial presence and on the accuracy in a pointing task. Second, driving the full eight screens, we explored the effect of embodied self-rotation using the same measures. In particular we compare navigation by rotating the world while the user is sitting stable to a stable world and a self-rotating user.Item The Diamond Laplace for Polygonal and Polyhedral Meshes(The Eurographics Association and John Wiley & Sons Ltd., 2021) Bunge, Astrid; Botsch, Mario; Alexa, Marc; Digne, Julie and Crane, KeenanWe introduce a construction for discrete gradient operators that can be directly applied to arbitrary polygonal surface as well as polyhedral volume meshes. The main idea is to associate the gradient of functions defined at vertices of the mesh with diamonds: the region spanned by a dual edge together with its corresponding primal element - an edge for surface meshes and a face for volumetric meshes. We call the operator resulting from taking the divergence of the gradient Diamond Laplacian. Additional vertices used for the construction are represented as affine combinations of the original vertices, so that the Laplacian operator maps from values at vertices to values at vertices, as is common in geometry processing applications. The construction is local, exactly the same for all types of meshes, and results in a symmetric negative definite operator with linear precision. We show that the accuracy of the Diamond Laplacian is similar or better compared to other discretizations. The greater versatility and generally good behavior come at the expense of an increase in the number of non-zero coefficients that depends on the degree of the mesh elements.Item Pose Correction by Space-Time Integration(The Eurographics Association, 2011) Esturo, Janick Martinez; Rössl, Christian; Fröhlich, Stefan; Botsch, Mario; Theisel, Holger; Peter Eisert and Joachim Hornegger and Konrad PolthierThe deformation of a given model into different poses is an important problem in computer graphics and computer animation. In a typical workflow, a carefully designed reference surface is deformed into a couple of poses, which can then act as a basis for interpolating arbitrarily intermediate poses. To this end the input poses should be free of geometric artifacts like self-intersections, since these degeneracies will be reproduced or even amplified by the interpolation. Not only are the resulting artifacts visually disturbing, they typically cause severe numerical problems for further downstream applications. In this paper we present an automatic approach for removing these geometric artifacts from a given set of mesh poses, while maintaining the original mesh connectivity. The deformation from the rest pose to a target pose is faithfully reproduced by integration of a smooth space-time vector field, which by construction guarantees the absence of self-intersections in the repaired target pose. Our approach is computationally efficient, and its effectiveness is demonstrated on a range of typical animation examples.Item OctaVis: A Virtual Reality System for Clinical Studies and Rehabilitation(The Eurographics Association, 2013) Zell, Eduard; Dyck, Eugen; Kohsik, Agnes; Grewe, Philip; Flentge, David; Winter, York; Piefke, Martina; Botsch, Mario; Hans-Christian Hege and Anna VilanovaBrain function disorders, resulting for instance from stroke, epilepsy, or other incidents can be partially recovered by rehabilitation training. Performing neuro-rehabilitation in virtual reality systems allows for training scenarios close to daily tasks, is easily adaptable to the patients' needs, is fully controllable by clinical staff, and guarantees patient safety at all times. In this paper, we describe the OCTAVIS system, a novel virtual reality platform developed primary for clinical studies with and rehabilitation training of patients with brain function disorders. To meet the special requirements for clinical use, our system has been designed with ease of use, ease of maintenance, patient safety, space and cost efficiency in mind. Our system has been successfully deployed to four hospitals, where it is used for rehabilitation training and clinical studies. We report first results of these studies, demonstrating that our system is immersive, easy to use, and supportive for rehabilitation purposes.Item A Compact Patch-Based Representation for Technical Mesh Models(The Eurographics Association, 2020) Kammann, Lars; Menzel, Stefan; Botsch, Mario; Krüger, Jens and Niessner, Matthias and Stückler, JörgWe present a compact and intuitive geometry representation for technical models initially given as triangle meshes. For CADlike models the defining features often coincide with the intersection between smooth surface patches. Our algorithm therefore first segments the input model into patches of constant curvature. The intersections between these patches are encoded through Bézier curves of adaptive degree, the patches enclosed by them are encoded by their (constant) mean and Gaussian curvatures. This sparse geometry representation enables intuitive understanding and editing by manipulating either the patches' curvature values and/or the feature curves. During decoding/reconstruction we exploit remeshing and hence are independent of the underlying triangulation, such that besides the feature curve topology no additional connectivity information has to be stored. We also enforce discrete developability for patches with vanishing Gaussian curvature in order to obtain straight ruling lines.Item Constructing L∞ Voronoi Diagrams in 2D and 3D(The Eurographics Association and John Wiley & Sons Ltd., 2022) Bukenberger, Dennis R.; Buchin, Kevin; Botsch, Mario; Campen, Marcel; Spagnuolo, MichelaVoronoi diagrams and their computation are well known in the Euclidean L2 space. They are easy to sample and render in generalized Lp spaces but nontrivial to construct geometrically. Especially the limit of this norm with p -> ∞ lends itself to many quad- and hex-meshing related applications as the level-set in this space is a hypercube. Many application scenarios circumvent the actual computation of L∞ diagrams altogether as known concepts for these diagrams are limited to 2D, uniformly weighted and axis-aligned sites. Our novel algorithm allows for the construction of generalized L∞ Voronoi diagrams. Although parts of the developed concept theoretically extend to higher dimensions it is herein presented and evaluated for the 2D and 3D case. It further supports individually oriented sites and allows for generating weighted diagrams with anisotropic weight vectors for individual sites. The algorithm is designed around individual sites, and initializes their cells with a simple meshed representation of a site's level-set. Hyperplanes between adjacent cells cut the initialization geometry into convex polyhedra. Non-cell geometry is filtered out based on the L∞ Voronoi criterion, leaving only the non-convex cell geometry. Eventually we conclude with discussions on the algorithms complexity, numerical precision and analyze the applicability of our generalized L∞ diagrams for the construction of Centroidal Voronoi Tessellations (CVT) using Lloyd's algorithm.Item ELASTIFACE: Matching and Blending Textured Faces(ACM, 2013) Zell, Eduard; Botsch, Mario; Forrester Cole and Cindy GrimmIn this paper we present ELASTIFACE, a simple and versatile method for establishing correspondence between textured face models, either for the construction of a blend-shape facial rig or for the exploration of new characters by morphing between a set of input models. While there exists a wide variety of approaches for inter-surface mapping and mesh morphing, most techniques are not suitable for our application: They either require the insertion of additional vertices, are limited to topological planes or spheres, are restricted to near-isometric input meshes, and/or are algorithmically and computationally involved. In contrast, our method extends linear non-rigid registration techniques to allow for strongly varying input geometries. It is geometrically intuitive, simple to implement, computationally efficient, and robustly handles highly non-isometric input models. In order to match the requirements of other applications, such as recent perception studies, we further extend our geometric matching to the matching of input textures and morphing of geometries and rendering styles.Item Robust Articulated-ICP for Real-Time Hand Tracking(The Eurographics Association and John Wiley & Sons Ltd., 2015) Tagliasacchi, Andrea; Schröder, Matthias; Tkach, Anastasia; Bouaziz, Sofien; Botsch, Mario; Pauly, Mark; Mirela Ben-Chen and Ligang LiuWe present a robust method for capturing articulated hand motions in realtime using a single depth camera. Our system is based on a realtime registration process that accurately reconstructs hand poses by fitting a 3D articulated hand model to depth images. We register the hand model using depth, silhouette, and temporal information. To effectively map low-quality depth maps to realistic hand poses, we regularize the registration with kinematic and temporal priors, as well as a data-driven prior built from a database of realistic hand poses. We present a principled way of integrating such priors into our registration optimization to enable robust tracking without severely restricting the freedom of motion. A core technical contribution is a new method for computing tracking correspondences that directly models occlusions typical of single-camera setups. To ensure reproducibility of our results and facilitate future research, we fully disclose the source code of our implementation.Item VMV 2022: Frontmatter(The Eurographics Association, 2022) Bender, Jan; Botsch, Mario; Keim, Daniel A.; Bender, Jan; Botsch, Mario; Keim, Daniel A.