26-Issue 3

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https://diglib.eg.org/handle/10.2312/131

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Markerless 4 gestures 6 DOF real-time visual tracking of the human hand with automatic initialization
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Schlattmann, Markus; Kahlesz, Ferenc; Sarlette, Ralf; Klein, Reinhard
In this paper we present a novel computer vision based hand-tracking technique, which is capable of robustly tracking 6+4DOF of the human hand in real-time (at least 25 frames per second) with the help of 3 (or more) off-the-shelf consumer cameras. 6+4DOF means that the system can track the global pose (6 continuous parameters for translation and rotation) of 4 different gestures. A key feature of our system is its fully automatic real-time initialization procedure, which, along with a sound tracking-lost detector, makes the system fit for real-world applications. Because of this, our method acts as an enabling technology for uncumbersome hand-based 3D Human-Computer-Interaction (HCI). Previously, using the hand as an at least 6DOF input device involved the use of either datagloves or markers. Using our tracking we evaluated the use of the hand as an input device for two prevalent Virtual Reality applications: fly-through exploration of a virtual world and a simple digital assembly simulation.
Global Illumination using Photon Ray Splatting
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Herzog, Robert; Havran, Vlastimil; Kinuwaki, Shinichi; Myszkowski, Karol; Seidel, Hans-Peter
We present a novel framework for efficiently computing the indirect illumination in diffuse and moderately glossy scenes using density estimation techniques. Many existing global illumination approaches either quickly compute an overly approximate solution or perform an orders of magnitude slower computation to obtain high-quality results for the indirect illumination. The proposed method improves photon density estimation and leads to significantly better visual quality in particular for complex geometry, while only slightly increasing the computation time. We perform direct splatting of photon rays, which allows us to use simpler search data structures. Since our density estimation is carried out in ray space rather than on surfaces, as in the commonly used photon mapping algorithm, the results are more robust against geometrically incurred sources of bias. This holds also in combination with final gathering where photon mapping often overestimates the illumination near concave geometric features. In addition, we show that our photon splatting technique can be extended to handle moderately glossy surfaces and can be combined with traditional irradiance caching for sparse sampling and filtering in image space.
Visibility Sampling on GPU and Applications
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Eisemann, Elmar; Decoret, Xavier
In this paper, we show how recent GPUs can be used to very efficiently and conveniently sample the visibility between two surfaces, given a set of occluding triangles. We use bitwise arithmetics to evaluate, encode, and combine the samples blocked by each triangle. In particular, the number of operations is almost independent of the number of samples. Our method requires no CPU/GPU transfers, is fully implemented as geometric, vertex and fragment shaders, and thus does not impose to modify the way the geometry is sent to the graphics card. We finally present applications to soft shadows, and visibility analysis for level design.
Interactive Visual Workspaces with Dynamic Foveal Areas and Adaptive Composite Interfaces
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Cotting, Daniel; Gross, Markus
This paper presents novel techniques and metaphors for on-demand visual workspaces in everyday office environments, providing space-efficient, flexible and highly interactive graphical user interfaces using projected displays. For increased resolution, contents personalization and interactive visualization, the users can augment the large-scale projections with dynamic high-resolution foveal enhancements using a pocket light metaphor. To further optimize the presentation at a given resolution, the design of the displays can be modified interactively, and like a jigsaw puzzle, the layout can be customized using an adaptive compositing approach which supports free-form focus-and-context rendering. With a unified intensity-based tracking approach, we allow for natural multi-touch interaction with the information space through bare hands, pointers and pens on arbitrary surfaces.
Adaptive Space Deformations Based on Rigid Cells
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Botsch, Mario; Pauly, Mark; Wicke, Martin; Gross, Markus
We propose a new adaptive space deformation method for interactive shape modeling. A novel energy formulation based on elastically coupled volumetric cells yields intuitive detail preservation even under large deformations. By enforcing rigidity of the cells, we obtain an extremely robust numerical solver for the resulting nonlinear optimization problem. Scalability is achieved using an adaptive spatial discretization that is decoupled from the resolution of the embedded object. Our approach is versatile and easy to implement, supports thin-shell and solid deformations of 2D and 3D objects, and is applicable to arbitrary sample-based representations, such as meshes, triangle soups, or point clouds.
3D Video Billboard Clouds
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Waschbuesch, Michael; Wuermlin, Stephan; Gross, Markus
3D video billboard clouds reconstruct and represent a dynamic three-dimensional scene using displacement-mapped billboards. They consist of geometric proxy planes augmented with detailed displacement maps and combine the generality of geometry-based 3D video with the regularization properties of image-based 3D video. 3D video billboards are an image-based representation placed in the disparity space of the acquisition cameras and thus provide a regular sampling of the scene with a uniform error model. We propose a general geometry filtering framework which generates time-coherent models and removes reconstruction and quantization noise as well as calibration errors. This replaces the complex and time-consuming sub-pixel matching process in stereo reconstruction with a bilateral filter. Rendering is performed using a GPU-accelerated algorithm which generates consistent view-dependent geometry and textures for each individual frame. In addition, we present a semi-automatic approach for modeling dynamic three-dimensional scenes with a set of multiple 3D video billboards clouds.
High-Quality Adaptive Soft Shadow Mapping
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Guennebaud, Gael; Barthe, Loic; Paulin, Mathias
The recent soft shadow mapping technique [GBP06] allows the rendering in real-time of convincing soft shadows on complex and dynamic scenes using a single shadow map. While attractive, this method suffers from shadow overestimation and becomes both expensive and approximate when dealing with large penumbrae. This paper proposes new solutions removing these limitations and hence providing an efficient and practical technique for soft shadow generation. First, we propose a new visibility computation procedure based on the detection of occluder contours, that is more accurate and faster while reducing aliasing. Secondly, we present a shadow map multi-resolution strategy keeping the computation complexity almost independent on the light size while maintaining high-quality rendering. Finally, we propose a view-dependent adaptive strategy, that automatically reduces the screen resolution in the region of large penumbrae, thus allowing us to keep very high frame rates in any situation.
Consistent Viewing and Interaction for Multiple Users in Projection-Based VR Systems
(The Eurographics Association and Blackwell Publishing Ltd, 2007) De Haan, Gerwin; Molenaar, Rene; Koutek, Michal; Post, Frits H.
In projection-based Virtual Reality (VR) systems, typically only one headtracked user views stereo images rendered from the correct view position. For other users, who are presented a distorted image, moving with the first user s head motion, it is difficult to correctly view and interact with 3D objects in the virtual environment. In close-range VR systems, such as the Virtual Workbench, distortion effects are especially large because objects are within close range and users are relatively far apart. On these systems, multi-user collaboration proves to be difficult. In this paper, we analyze the problem and describe a novel, easy to implement method to prevent and reduce image distortion and its negative effects on close-range interaction task performance. First, our method combines a shared camera model and view distortion compensation. It minimizes the overall distortion for each user, while important user-personal objects such as interaction cursors, rays and controls remain distortion-free. Second, our method retains co-location for interaction techniques to make interaction more consistent. We performed a user experiment on our Virtual Workbench to analyze user performance under distorted view conditions with and without the use of our method. Our findings demonstrate the negative impact of view distortion on task performance and the positive effect our method introduces. This indicates that our method can enhance the multi-user collaboration experience on close-range, projection-based VR systems.
Serious Games: Broadening Games Impact Beyond Entertainment
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Sawyer, Ben
Computer and videogames for many years has been an island of technology and design innovation largely left to itself as it morphed from a cottage business into a global media and software industry. While there have been pockets of derivative activity related to games and game technology only in the last half-dozen years has there been a real movement toward exploiting this industry in many new and exciting ways.Today the general use of games and game technologies for purposes beyond entertainment is collectively referred to as serious games. The Serious Games Initiative was formed in 2002 and since its inception has been among a number of critical efforts that has helped open up the world and many disciplines to the ideas and innovations that may be sourced from the commercial, independent, and academic game fields. This has been a person-by-person, project-by-project effort that not only has informed us about the potential of games but also in how you merge innovation and innovators from one discipline with those in another.In this talk we will explore the total gamut of the serious games field identifying past the obvious how games and game technologies are being applied to problems in a wide array of areas including healthcare, productivity, visualization, science, and of course training and education. Once a proper definition of serious games is established the talk will focus on the current state of the field as it relates to research and infrastructure issues that are needed to make the difference between seeing serious games take hold as a major new practice or having it devolve into another trend of the moment lost to history.
A Bidirectional Light Field - Hologram Transform
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Ziegler, Remo; Bucheli, Simon; Ahrenberg, Lukas; Magnor, Marcus; Gross, Markus
In this paper, we propose a novel framework to represent visual information. Extending the notion of conventional image-based rendering, our framework makes joint use of both light fields and holograms as complementary representations. We demonstrate how light fields can be transformed into holograms, and vice versa. By exploiting the advantages of either representation, our proposed dual representation and processing pipeline is able to overcome the limitations inherent to light fields and holograms alone. We show various examples from synthetic and real light fields to digital holograms demonstrating advantages of either representation, such as speckle-free images, ghosting-free images, aliasing-free recording, natural light recording, aperture-dependent effects and real-time rendering which can all be achieved using the same framework. Capturing holograms under white light illumination is one promising application for future work.
A Generic Pigment Model for Digital Painting
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Xu, Songhua; Tan, Haisheng; Jiao, Xiantao; Lau, Francis C.M.; Pan, Yunhe
Depth-of-Field Rendering by Pyramidal Image Processing
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Kraus, M.; Strengert, M.
We present an image-based algorithm for interactive rendering depth-of-field effects in images with depth maps. While previously published methods for interactive depth-of-field rendering suffer from various rendering artifacts such as color bleeding and sharpened or darkened silhouettes, our algorithm achieves a significantly improved image quality by employing recently proposed GPU-based pyramid methods for image blurring and pixel disocclusion. Due to the same reason, our algorithm offers an interactive rendering performance on modern GPUs and is suitable for real-time rendering for small circles of confusion. We validate the image quality provided by our algorithm by side-by-side comparisons with results obtained by distributed ray tracing.
Metropolis Instant Radiosity
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Segovia, B.; Iehl, J.C.; Peroche, B.
We present Metropolis Instant Radiosity (MIR), an unbiased algorithm to solve the Light Transport problem. MIR is a hybrid technique which consists in representing the incoming radiance field by a set of Virtual Point Lights (V PLs) and in computing the response of all sensors in the scene (i.e. camera captors) by accumulating their contributions. In contrast to other similar approaches, we propose to sample the VPLs with an innovative Multiple-try Metropolis-Hastings (MTMH) Algorithm: the goal is to build an efficient, aggressive, and unconditionally robust variance reduction method that works well regardless of the scene layout. Finally, we present a fast ray tracing implementation using MIR and show how our complete rendering pipeline can produce high-quality and high-resolution pictures in a few seconds.
Volume Preservation of Multiresolution Meshes
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Sauvage, Basile; Hahmann, Stefanie; Bonneau, Georges-Pierre
Geometric constraints have proved to be efficient for enhancing the realism of shape animation. The present paper addresses the computation and the preservation of the volume enclosed by multiresolution meshes. A wavelet based representation allows the mesh to be handled at any level of resolution. The key contribution is the calculation of the volume as a trilinear form with respect to the multiresolution coefficients. Efficiency is reached thanks to the pre-processing of a sparse 3D data structure involving the transposition of the filters while represented as a lifting scheme. A versatile and interactive method for preserving the volume during a deformation process is then proposed. It is based on a quadratic minimization subject to a linearization of the volume constraint. A closed form of the solution is derived.
Bitmask Soft Shadows
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Schwarz, Michael; Stamminger, Marc
Recently, several real-time soft shadow algorithms have been introduced which all compute a single shadow map and use its texels to obtain a discrete scene representation. The resulting micropatches are backprojected onto the light source and the light areas occluded by them get accumulated to estimate overall light occlusion. This approach ignores patch overlaps, however, which can lead to objectionable artifacts. In this paper, we propose to determine the visibility of the light source with a bit field where each bit tracks the visibility of a sample point on the light source. This approach not only avoids overlapping-related artifacts but offers a solution to the important occluder fusion problem. Hence, it also becomes possible to correctly incorporate information from multiple depth maps. In addition, a new interpretation of the shadow map data is suggested which often provides superior visual results. Finally, we show how the search area for potential occluders can be reduced substantially.
A Finite Element Method on Convex Polyhedra
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Wicke, Martin; Botsch, Mario; Gross, Markus
We present a method for animating deformable objects using a novel finite element discretization on convex polyhedra. Our finite element approach draws upon recently introduced 3D mean value coordinates to define smooth interpolants within the elements. The mathematical properties of our basis functions guarantee convergence. Our method is a natural extension to linear interpolants on tetrahedra: for tetrahedral elements, the methods are identical. For fast and robust computations, we use an elasticity model based on Cauchy strain and stiffness warping.This more flexible discretization is particularly useful for simulations that involve topological changes, such as cutting or fracture. Since splitting convex elements along a plane produces convex elements, remeshing or subdivision schemes used in simulations based on tetrahedra are not necessary, leading to less elements after such operations. We propose various operators for cutting the polyhedral discretization. Our method can handle arbitrary cut trajectories, and there is no limit on how often elements can be split.
QuadCover - Surface Parameterization using Branched Coverings
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Kaelberer, Felix; Nieser, Matthias; Polthier, Konrad
We introduce an algorithm for the automatic computation of global parameterizations on arbitrary simplicial 2-manifolds, whose parameter lines are guided by a given frame field, for example, by principal curvature frames. The parameter lines are globally continuous and allow a remeshing of the surface into quadrilaterals. The algorithm converts a given frame field into a single vector field on a branched covering of the 2-manifold and generates an integrable vector field by a Hodge decomposition on the covering space. Except for an optional smoothing and alignment of the initial frame field, the algorithm is fully automatic and generates high quality quadrilateral meshes.
Real-Time Simulation of Thin Shells
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Choi, Min Gyu; Yong Woo, Seung; Ko, Hyeong-Seok
This paper proposes a real-time simulation technique for thin shells undergoing large deformation. Shells are thin objects such as leaves and papers that can be abstracted as 2D structures. Development of a satisfactory physical model that runs in real-time but produces visually convincing animation of thin shells has been remaining a challenge in computer graphics. Rather than resorting to shell theory which involves the most complex formulations in continuum mechanics, we adopt the energy functions from the discrete shells proposed by Grinspun et al. [GHDS03]. For real-time integration of the governing equation, we develop a modal warping technique for shells. This new simulation framework results from making extensions to the original modal warping technique [CK05] which was developed for the simulation of 3D solids. We report experimental results, which show that the proposed method runs in real-time even for large meshes, and that it can simulate large bending and/or twisting deformations with acceptable realism.
Contrast Restoration by Adaptive Countershading
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Krawczyk, Grzegorz; Myszkowski, Karol; Seidel, Hans-Peter
The ABSTRACT is to be in fully-justified italicized text, between two horizontal lines, in one-column format, below the author and affiliation information. Use the word Abstract as the title, in 9-point Times, boldface type, left-aligned to the text, initially capitalized. The abstract is to be in 9-point, single-spaced type. The abstract may be up to 3 inches (7.62 cm) long. Leave one blank line after the abstract, then add the subject categories according to the ACM Classification Index (see http://www.acm.org/class/1998/).
Pedestrian Reactive Navigation for Crowd Simulation: a Predictive Approach
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Paris, Sebastien; Pettre, Julien; Donikian, Stephane
This paper addresses the problem of virtual pedestrian autonomous navigation for crowd simulation. It describes a method for solving interactions between pedestrians and avoiding inter-collisions. Our approach is agent-based and predictive: each agent perceives surrounding agents and extrapolates their trajectory in order to react to potential collisions. We aim at obtaining realistic results, thus the proposed model is calibrated from experimental motion capture data. Our method is shown to be valid and solves major drawbacks compared to previous approaches such as oscillations due to a lack of anticipation. We first describe the mathematical representation used in our model, we then detail its implementation, and finally, its calibration and validation from real data.

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