004 Datenverarbeitung; Informatik
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- 2006 (8) (remove)
In today’s information society the vast technical progress and the sinking cost of information and communication technology provide new opportunities for information supply, and new technical support for communication and cooperation over distance. These trends also entail challenges such as supplying information that is adequate for a particular person in a specific situation as well as managing communication among geographically distributed parties efficiently. Context-aware systems that use sensors in order to analyse their environment and to adapt their behaviour. Yet, adequate tools for developing sensor-based infrastructures are missing. We have designed and developed Sens-ation, an open and generic service-oriented platform, which provides powerful, yet easy-to-use, tools to software developers who want to develop context-aware, sensor-based infrastructures. The service-oriented paradigm of Sens-ation enables standardised communication within individual infrastructures, between infrastructures and their sensors, but also among distributed infrastructures. On a whole, Sens-ation facilitates the development allowing developers to concentrate on the semantics of their infrastructures, and to develop innovative concepts and implementations of context-aware systems.
Recent radiometric compensation techniques make it possible to project images onto colored and textured surfaces. This is realized with projector-camera systems by scanning the projection surface on a per-pixel basis. With the captured information, a compensation image is calculated that neutralizes geometric distortions and color blending caused by the underlying surface. As a result, the brightness and the contrast of the input image is reduced compared to a conventional projection onto a white canvas. If the input image is not manipulated in its intensities, the compensation image can contain values that are outside the dynamic range of the projector. They will lead to clipping errors and to visible artifacts on the surface. In this article, we present a novel algorithm that dynamically adjusts the content of the input images before radiometric compensation is carried out. This reduces the perceived visual artifacts while simultaneously preserving a maximum of luminance and contrast. The algorithm is implemented entirely on the GPU and is the first of its kind to run in real-time.
Projector-based displays have been evolving tremendously in the last decade. Reduced costs and increasing capabilities have let to a widespread use for home entertainment and scientific visualization. The rapid development is continuing - techniques that allow seamless projection onto complex everyday environments such as textured walls, window curtains or bookshelfs have recently been proposed. Although cameras enable a completely automatic calibration of the systems, all previously described techniques rely on a precise mapping between projector and camera pixels. Global illumination effects such as reflections, refractions, scattering, dispersion etc. are completely ignored since only direct illumination is taken into account. We propose a novel method that applies the light transport matrix for performing an image-based radiometric compensation which accounts for all possible lighting effects. For practical application the matrix is decomposed into clusters of mutually influencing projector and camera pixels. The compensation is modeled as a linear equation system that can be solved separately for each cluster. For interactive compensation rates this model is adapted to enable an efficient implementation on programmable graphics hardware. Applying the light transport matrix's pseudo-inverse allows to separate the compensation into a computational expensive preprocessing step (computing the pseudo-inverse) and an on-line matrix-vector multiplication. The generalized mathematical foundation for radiometric compensation with projector-camera systems is validated with several experiments. We show that it is possible to project corrected imagery onto complex surfaces such as an inter-reflecting statuette and glass. The overall sharpness of defocused projections is increased as well. Using the proposed optimization for GPUs, real-time framerates are achieved.
Projector-Based Augmentation
(2006)
Projector-based augmentation approaches hold the potential of combining the advantages of well-establishes spatial virtual reality and spatial augmented reality. Immersive, semi-immersive and augmented visualizations can be realized in everyday environments – without the need for special projection screens and dedicated display configurations. Limitations of mobile devices, such as low resolution and small field of view, focus constrains, and ergonomic issues can be overcome in many cases by the utilization of projection technology. Thus, applications that do not require mobility can benefit from efficient spatial augmentations. Examples range from edutainment in museums (such as storytelling projections onto natural stone walls in historical buildings) to architectural visualizations (such as augmentations of complex illumination simulations or modified surface materials in real building structures). This chapter describes projector-camera methods and multi-projector techniques that aim at correcting geometric aberrations, compensating local and global radiometric effects, and improving focus properties of images projected onto everyday surfaces.
Die heute erhältlichen Web-Content Management-Systeme (WCMS) verfügen über ein umfangreiches und breit gefächertes Angebot an Funktionen, die weit über die, zur Redaktion und zum Management von Internetpräsentationen, not-wendigen Grundanforderungen hinausgehen. Das macht diese Systeme in ih-ren Einsatz sehr flexibel und deckt vielfältige Anforderungen der Endanwender ab. Andererseits steigt durch die dadurch bedingte Komplexität der Arbeitsauf-wand erheblich und die Bedien- und Benutzerfreundlichkeit sinkt. Gerade für kleinere Internetpräsentationen, die ohne aufwendige Interaktionsmöglichkeiten aber auf häufig wechselndem Informationsangeboten aufwarten, wäre dies in seiner Grundfunktionalität reduziertes System vorteilhaft. Ein solches reduziertes Web-Content Management-System soll während der Diplomarbeit entworfen und beispielhaft implementiert werden. Als Ausgangs- und Orientierungspunkt soll hierzu die Internetpräsentation der Professur Informations- und Wissensverarbeitung dienen. Zur softwaretechnischen Umsetzung sind PHP und MySQL in Verbindung mit regulären HTML und CSS zu be-nutzen. Für das weitere Vorgehen müssen zunächst die Struktur und der Aufbau der Internetpräsentation der Professur analysiert, strukturiert und formalisiert werden. Anschließend sind die am häufigsten professionell genutzten Webcontent-Managementsysteme (TYPO3 und weitere siehe www.opensourcecms.com) hinsichtlich der durch sie angebotenen Grundfunktionalitäten und der verwen-deten Templates und Vorlagen zu untersuchen. Die aus dieser Analyse resultierenden Ergebnisse sind Ausgangspunkt für die Anforderungsdefinition des zu erstellenden Mini-WCMS. Anschließend ist eine prototypische Implementierung des theoretisch entstan-denen Systems, zugeschnitten auf die speziellen Bedürfnisse der Professur, vorzunehmen und hinsichtlich seiner Eignung zu diskutieren.
Early sensor-based infrastructures were often developed by experts with a thorough knowledge of base technology for sensing information, for processing the captured data, and for adapting the system’s behaviour accordingly. In this paper we argue that also end-users should be able to configure Ubiquitous Computing environments. We introduce the CollaborationBus application: a graphical editor that provides abstractions from base technology and thereby allows multifarious users to configure Ubiquitous Computing environments. By composing pipelines users can easily specify the information flows from selected sensors via optional filters for processing the sensor data to actuators changing the system behaviour according to the users’ wishes. Users can compose pipelines for both home and work environments. An integrated sharing mechanism allows them to share their own compositions, and to reuse and build upon others’ compositions. Real-time visualisations help them understand how the information flows through their pipelines. In this paper we present the concept, implementation, and early user feedback of the CollaborationBus application.
We propose a novel method that applies the light transport matrix for performing an image-based radiometric compensation which accounts for all possible types of light modulation. For practical application the matrix is decomposed into clusters of mutually influencing projector and camera pixels. The compensation is modeled as a linear system that can be solved with respect to the projector patterns. Precomputing the inverse light transport in combination with an efficient implementation on the GPU makes interactive compensation rates possible. Our generalized method unifies existing approaches that address individual problems. Based on examples, we show that it is possible to project corrected images onto complex surfaces such as an inter-reflecting statuette, glossy wallpaper, or through highly-refractive glass. Furthermore, we illustrate that a side-effect of our approach is an increase in the overall sharpness of defocused projections.
For efficient distant cooperation the members of workgroups need information about each other. This need for information disclosure often conflicts with the users' wishes for privacy. In the literature often reciprocity is suggested as a solution to this trade-off. Yet, this conception of reciprocity and its enforcement by systems does not match reality. In this paper we present our study's major findings investigating the role of reciprocity among which we found that participants greatly disregarded the above conception. Additionally we discuss their significant implications for the design of systems seeking to disclose personal information.