TY - CHAP A1 - Bimber, Oliver T1 - HOLOGRAPHICS: Combining Holograms with Interactive Computer Graphics T2 - New Directions in Holography and Speckles N2 - Among all imaging techniques that have been invented throughout the last decades, computer graphics is one of the most successful tools today. Many areas in science, entertainment, education, and engineering would be unimaginable without the aid of 2D or 3D computer graphics. The reason for this success story might be its interactivity, which is an important property that is still not provided efficiently by competing technologies – such as holography. While optical holography and digital holography are limited to presenting a non-interactive content, electroholography or computer generated holograms (CGH) facilitate the computer-based generation and display of holograms at interactive rates [2,3,29,30]. Holographic fringes can be computed by either rendering multiple perspective images, then combining them into a stereogram [4], or simulating the optical interference and calculating the interference pattern [5]. Once computed, such a system dynamically visualizes the fringes with a holographic display. Since creating an electrohologram requires processing, transmitting, and storing a massive amount of data, today’s computer technology still sets the limits for electroholography. To overcome some of these performance issues, advanced reduction and compression methods have been developed that create truly interactive electroholograms. Unfortunately, most of these holograms are relatively small, low resolution, and cover only a small color spectrum. However, recent advances in consumer graphics hardware may reveal potential acceleration possibilities that can overcome these limitations [6]. In parallel to the development of computer graphics and despite their non-interactivity, optical and digital holography have created new fields, including interferometry, copy protection, data storage, holographic optical elements, and display holograms. Especially display holography has conquered several application domains. Museum exhibits often use optical holograms because they can present 3D objects with almost no loss in visual quality. In contrast to most stereoscopic or autostereoscopic graphics displays, holographic images can provide all depth cues—perspective, binocular disparity, motion parallax, convergence, and accommodation—and theoretically can be viewed simultaneously from an unlimited number of positions. Displaying artifacts virtually removes the need to build physical replicas of the original objects. In addition, optical holograms can be used to make engineering, medical, dental, archaeological, and other recordings—for teaching, training, experimentation and documentation. Archaeologists, for example, use optical holograms to archive and investigate ancient artifacts [7,8]. Scientists can use hologram copies to perform their research without having access to the original artifacts or settling for inaccurate replicas. Optical holograms can store a massive amount of information on a thin holographic emulsion. This technology can record and reconstruct a 3D scene with almost no loss in quality. Natural color holographic silver halide emulsion with grain sizes of 8nm is today’s state-of-the-art [14]. Today, computer graphics and raster displays offer a megapixel resolution and the interactive rendering of megabytes of data. Optical holograms, however, provide a terapixel resolution and are able to present an information content in the range of terabytes in real-time. Both are dimensions that will not be reached by computer graphics and conventional displays within the next years – even if Moore’s law proves to hold in future. Obviously, one has to make a decision between interactivity and quality when choosing a display technology for a particular application. While some applications require high visual realism and real-time presentation (that cannot be provided by computer graphics), others depend on user interaction (which is not possible with optical and digital holograms). Consequently, holography and computer graphics are being used as tools to solve individual research, engineering, and presentation problems within several domains. Up until today, however, these tools have been applied separately. The intention of the project which is summarized in this chapter is to combine both technologies to create a powerful tool for science, industry and education. This has been referred to as HoloGraphics. Several possibilities have been investigated that allow merging computer generated graphics and holograms [1]. The goal is to combine the advantages of conventional holograms (i.e. extremely high visual quality and realism, support for all depth queues and for multiple observers at no computational cost, space efficiency, etc.) with the advantages of today’s computer graphics capabilities (i.e. interactivity, real-time rendering, simulation and animation, stereoscopic and autostereoscopic presentation, etc.). The results of these investigations are presented in this chapter. KW - Erweiterte Realität KW - CGI KW - Hologramm KW - Projektionsapparat KW - Rendering KW - Scanning KW - Reconstruction KW - computer grafik KW - computer graphics Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-7365 ER - TY - CHAP A1 - Bimber, Oliver T1 - Projector-Based Augmentation T2 - Emerging Technologies of Augmented Reality: Interfaces & Design N2 - 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. KW - Erweiterte Realität KW - Virtuelle Realität KW - Projektionsverfahren KW - CGI KW - Bildbasiertes Rendering KW - Rendering KW - Projektor-Kamera Systeme KW - Multi-Projektor Systeme KW - projector-camera systems KW - multi-projector systems KW - spatial augmented reality Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20111215-7353 ER - TY - THES A1 - Schollmeyer, Andre T1 - Efficient and High-Quality Rendering of Higher-Order Geometric Data Representations N2 - Computer-Aided Design (CAD) bezeichnet den Entwurf industrieller Produkte mit Hilfe von virtuellen 3D Modellen. Ein CAD-Modell besteht aus parametrischen Kurven und Flächen, in den meisten Fällen non-uniform rational B-Splines (NURBS). Diese mathematische Beschreibung wird ebenfalls zur Analyse, Optimierung und Präsentation des Modells verwendet. In jeder dieser Entwicklungsphasen wird eine unterschiedliche visuelle Darstellung benötigt, um den entsprechenden Nutzern ein geeignetes Feedback zu geben. Designer bevorzugen beispielsweise illustrative oder realistische Darstellungen, Ingenieure benötigen eine verständliche Visualisierung der Simulationsergebnisse, während eine immersive 3D Darstellung bei einer Benutzbarkeitsanalyse oder der Designauswahl hilfreich sein kann. Die interaktive Darstellung von NURBS-Modellen und -Simulationsdaten ist jedoch aufgrund des hohen Rechenaufwandes und der eingeschränkten Hardwareunterstützung eine große Herausforderung. Diese Arbeit stellt vier neuartige Verfahren vor, welche sich mit der interaktiven Darstellung von NURBS-Modellen und Simulationensdaten befassen. Die vorgestellten Algorithmen nutzen neue Fähigkeiten aktueller Grafikkarten aus, um den Stand der Technik bezüglich Qualität, Effizienz und Darstellungsgeschwindigkeit zu verbessern. Zwei dieser Verfahren befassen sich mit der direkten Darstellung der parametrischen Beschreibung ohne Approximationen oder zeitaufwändige Vorberechnungen. Die dabei vorgestellten Datenstrukturen und Algorithmen ermöglichen die effiziente Unterteilung, Klassifizierung, Tessellierung und Darstellung getrimmter NURBS-Flächen und einen interaktiven Ray-Casting-Algorithmus für die Isoflächenvisualisierung von NURBSbasierten isogeometrischen Analysen. Die weiteren zwei Verfahren beschreiben zum einen das vielseitige Konzept der programmierbaren Transparenz für illustrative und verständliche Visualisierungen tiefenkomplexer CAD-Modelle und zum anderen eine neue hybride Methode zur Reprojektion halbtransparenter und undurchsichtiger Bildinformation für die Beschleunigung der Erzeugung von stereoskopischen Bildpaaren. Die beiden letztgenannten Ansätze basieren auf rasterisierter Geometrie und sind somit ebenfalls für normale Dreiecksmodelle anwendbar, wodurch die Arbeiten auch einen wichtigen Beitrag in den Bereichen der Computergrafik und der virtuellen Realität darstellen. Die Auswertung der Arbeit wurde mit großen, realen NURBS-Datensätzen durchgeführt. Die Resultate zeigen, dass die direkte Darstellung auf Grundlage der parametrischen Beschreibung mit interaktiven Bildwiederholraten und in subpixelgenauer Qualität möglich ist. Die Einführung programmierbarer Transparenz ermöglicht zudem die Umsetzung kollaborativer 3D Interaktionstechniken für die Exploration der Modelle in virtuellenUmgebungen sowie illustrative und verständliche Visualisierungen tiefenkomplexer CAD-Modelle. Die Erzeugung stereoskopischer Bildpaare für die interaktive Visualisierung auf 3D Displays konnte beschleunigt werden. Diese messbare Verbesserung wurde zudem im Rahmen einer Nutzerstudie als wahrnehmbar und vorteilhaft befunden. N2 - In computer-aided design (CAD), industrial products are designed using a virtual 3D model. A CAD model typically consists of curves and surfaces in a parametric representation, in most cases, non-uniform rational B-splines (NURBS). The same representation is also used for the analysis, optimization and presentation of the model. In each phase of this process, different visualizations are required to provide an appropriate user feedback. Designers work with illustrative and realistic renderings, engineers need a comprehensible visualization of the simulation results, and usability studies or product presentations benefit from using a 3D display. However, the interactive visualization of NURBS models and corresponding physical simulations is a challenging task because of the computational complexity and the limited graphics hardware support. This thesis proposes four novel rendering approaches that improve the interactive visualization of CAD models and their analysis. The presented algorithms exploit latest graphics hardware capabilities to advance the state-of-the-art in terms of quality, efficiency and performance. In particular, two approaches describe the direct rendering of the parametric representation without precomputed approximations and timeconsuming pre-processing steps. New data structures and algorithms are presented for the efficient partition, classification, tessellation, and rendering of trimmed NURBS surfaces as well as the first direct isosurface ray-casting approach for NURBS-based isogeometric analysis. The other two approaches introduce the versatile concept of programmable order-independent semi-transparency for the illustrative and comprehensible visualization of depth-complex CAD models, and a novel method for the hybrid reprojection of opaque and semi-transparent image information to accelerate stereoscopic rendering. Both approaches are also applicable to standard polygonal geometry which contributes to the computer graphics and virtual reality research communities. The evaluation is based on real-world NURBS-based models and simulation data. The results show that rendering can be performed directly on the underlying parametric representation with interactive frame rates and subpixel-precise image results. The computational costs of additional visualization effects, such as semi-transparency and stereoscopic rendering, are reduced to maintain interactive frame rates. The benefit of this performance gain was confirmed by quantitative measurements and a pilot user study. KW - Rendering KW - CAD KW - NURBS KW - Computer-Aided Design KW - Isogeometric Analysis KW - Graphics hardware Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20181120-38234 ER - TY - JOUR A1 - Kreskowski, Adrian A1 - Rendle, Gareth A1 - Fröhlich, Bernd T1 - Efficient Direct Isosurface Rasterization of Scalar Volumes JF - Computer Graphics Forum N2 - In this paper we propose a novel and efficient rasterization-based approach for direct rendering of isosurfaces. Our method exploits the capabilities of task and mesh shader pipelines to identify subvolumes containing potentially visible isosurface geometry, and to efficiently extract primitives which are consumed on the fly by the rasterizer. As a result, our approach requires little preprocessing and negligible additional memory. Direct isosurface rasterization is competitive in terms of rendering performance when compared with ray-marching-based approaches, and significantly outperforms them for increasing resolution in most situations. Since our approach is entirely rasterization based, it affords straightforward integration into existing rendering pipelines, while allowing the use of modern graphics hardware features, such as multi-view stereo for efficient rendering of stereoscopic image pairs for geometry-bound applications. Direct isosurface rasterization is suitable for applications where isosurface geometry is highly variable, such as interactive analysis scenarios for static and dynamic data sets that require frequent isovalue adjustment. KW - Rendering KW - Rastergrafik KW - Visualisierung KW - Maschinelles Sehen KW - isosurface KW - rendering KW - rasterization Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20230525-63835 UR - https://onlinelibrary.wiley.com/doi/full/10.1111/cgf.14670 VL - 2022 IS - Volume 4, Issue 7 SP - 215 EP - 226 PB - Wiley Blackwell CY - Oxford ER -