Volume 26 (2007)

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https://diglib.eg.org/handle/10.2312/128

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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.
Unpopping: Solving the Image-Space Blend Problem for Smooth Discrete LOD Transitions
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Giegl, Markus; Wimmer, Michael
This paper presents a new, simple and practical algorithm to avoid artifacts when switching between discrete levels of detail (LOD) by smoothly blending LOD representations in image space. We analyse the alternatives of conventional alpha-blending and so-called late-switching (the switching of LODs far enough from the eye-point), widely thought to solve the LOD switching discontinuity problem, and conclude that they either do not work in practice, or defeat the concept of LODs. In contrast we show that our algorithm produces visually pleasing blends for static and animated discrete LODs, for discrete LODs with different types of LOD representations (e.g. billboards and meshes) and even to some extent totally different objects with similar spatial extent, with a very small runtime overhead.
Smooth Piecewise Polynomial Blending Operations for Implicit Shapes
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Li, Q.
In this paper, we present a new set of blending operations for implicitly defined geometric shapes. The proposed shape operators are piecewise polynomial and blending range controllable, and can be constructed to any required degree of smoothness. The key idea behind these techniques is the introduction of the concept of the smooth absolute functions, which in turn lead to the definition of smooth maximum functions. These novel generalized absolute functions can be constructed recursively or through a recursively defined functions, and can thus be computed cheaply. In addition, the underlying mathematical descriptions of these shape operations are very simple and elegant.
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.
Data-driven Tetrahedral Mesh Subdivision
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Rodriguez, L.; Navazo, I.; Vinacua, A.
Given a tetrahedral mesh immersed in a voxel model, we present a method to refine the mesh to reduce the discrepancy between interpolated values based on either scheme at arbitrary locations. An advantage of the method presented is that it requires few subdivisions and all decisions are made locally at each tetrahedron. We discuss the algorithm s performance and applications.
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.
Erratum
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Langdon, W. B.
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.
Digital Mosaic Frameworks - An Overview
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Battiato, S.; Di Blasi, G.; Farinella, G. M.; Gallo, G.
Art often provides valuable hints for technological innovations especially in the field of Image Processing and Computer Graphics. In this paper we survey in a unified framework several methods to transform raster input images into good quality mosaics. For each of the major different approaches in literature the paper reports a short description and a discussion of the most relevant issues. To complete the survey comparisons among the different techniques both in terms of visual quality and computational complexity are provided.
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.
Expeditious Modelling of Virtual Urban Environments with Geospatial L-systems
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Coelho, A.; Bessa, M.; Sousa, A. Augusto; Ferreira, F. Nunes
L-systems have been used in Computer Graphics, namely for modelling plants, as well as in a few experiments to model urban environments. However, the lack of geospatial awareness is a limitation and in spite of some developments like open L-systems, that introduced the ability to communicate with the environment, there was a need for more flexibility. This paper presents Geospatial L-systems, a new extension of L-systems that incorporates geospatial awareness, and shows an application in the area of expeditious modelling of urban environments. A modelling system, named XL3D, generates virtual urban environments automatically from a XML based document that contains a modelling specification and accesses data sources in an interoperable way. The integration of geospatial L-systems in this modelling system has increased the potential for automation and the potential to generate virtual urban environments with a higher level of detail and visual fidelity, with a lower level of complexity of the modelling processes. These facts are shown in a case study where a virtual urban environment, taken from an area in the Porto downtown, is generated by this solution.
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.
Graphics-Based Learning in First-Year Computer Science
(The Eurographics Association and Blackwell Publishing Ltd, 2007) Davis, T. A.
This paper proposes a method for teaching a first-year course in computer science using graphics-based problems as the teaching medium. Specifically, we present a method for instruction in programming using a semester-long project of developing a ray tracer. This effort is part of a larger project, known as, in which a broad range of undergraduate courses are taught using computer graphics as the motivating application. An overview of this project is provided, along with description and results from the first trial CS2 course instructed using this technique.
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.

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