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Item Recreating Early Islamic Glass Lamp Lighting(The Eurographics Association, 2009) Jr., Joseph T. Kider; Fletcher, Rebecca L.; Yu, Nancy; Holod, Renata; Chalmers, Alan; Badler, Norman I.; Kurt Debattista and Cinzia Perlingieri and Denis Pitzalis and Sandro SpinaEarly Islamic light sources are not simple, static, uniform points, and the fixtures themselves are often combinations of glass, water, fuel and flame. Various physically based renderers such as Radiance are widely used for modeling ancient architectural scenes; however they rarely capture the true ambiance of the environment due to subtle lighting effects. Specifically, these renderers often fail to correctly model complex caustics produced by glass fixtures, water level, and fuel sources.While the original fixtures of the 8th through 10th century Mosque of Cordoba in Spain have not survived, we have applied information gathered from earlier and contemporary sites and artifacts, including those from Byzantium, to assume that it was illuminated by either single jar lamps or supported by polycandela that cast unique downward caustic lighting patterns which helped individuals to navigate and to read. To re-synthesize such lighting, we gathered experimental archaeological data and investigated and validated how various water levels and glass fixture shapes, likely used during early Islamic times, changed the overall light patterns and downward caustics. In this paper, we propose a technique called Caustic Cones, a novel data-driven method to "shape" the light emanating from the lamps to better recreate the downward lighting without resorting to computationally expensive photon mapping renderers.Additionally, we demonstrate on a rendering of the Mosque of Cordoba how our approach greatly benefits archaeologists and architectural historians by providing a more authentic visual simulation of early Islamic glass lamp lighting.Item High Dynamic Range Video for Cultural Heritage Documentation and Experimental Archaeology(The Eurographics Association, 2010) Happa, Jassim; Artusi, Alessandro; Czanner, Silvester; Chalmers, Alan; Alessandro Artusi and Morwena Joly and Genevieve Lucet and Denis Pitzalis and Alejandro RibesVideo recording and photography are frequently used to document Cultural Heritage (CH) objects and sites. High Dynamic Range (HDR) imaging is increasingly being used as it allows a wider range of light to be considered that most current technologies are unable to natively acquire and reproduce. HDR video content however has only recently become possible at desirable, high definition resolution and dynamic range. In this paper we explore the potential use of a 20 f-stop HDR video camera for CH documentation and experimental archaeology purposes. We discuss data acquisition of moving caustics, flames, distant light and in participating media. Comparisons of Low Dynamic Range (LDR) and HDR content are made to illustrate the additional data that this new technology is able to capture, and the benefits this is likely to bring to CH documentation and experimental archaeology.Item Point Cloud Segmentation for Cultural Heritage Sites(The Eurographics Association, 2011) Spina, Sandro; Debattista, Kurt; Bugeja, Keith; Chalmers, Alan; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolOver the past few years, the acquisition of 3D point information representing the structure of real-world objects has become common practice in many areas. This is particularly true in the Cultural Heritage (CH) domain, where point clouds reproducing important and usually unique artifacts and sites of various sizes and geometric complexities are acquired. Specialized software is then usually used to process and organise this data. This paper addresses the problem of automatically organising this raw data by segmenting point clouds into meaningful subsets. This organisation over raw data entails a reduction in complexity and facilitates the post-processing effort required to work with the individual objects in the scene. This paper describes an efficient two-stage segmentation algorithm which is able to automatically partition raw point clouds. Following an intial partitioning of the point cloud, a RanSaC-based plane fitting algorithm is used in order to add a further layer of abstraction. A number of potential uses of the newly processed point cloud are presented; one of which is object extraction using point cloud queries. Our method is demonstrated on three point clouds ranging from 600K to 1.9M points. One of these point clouds was acquired from the pre-historic temple of Mnajdra consistsing of multiple adjacent complex structures.Item Rendering Interior Cultural Heritage Scenes Using Image-based Shooting(The Eurographics Association, 2011) Happa, Jassim; Bashford-Rogers, Tom; Debattista, Kurt; Chalmers, Alan; A. Day and R. Mantiuk and E. Reinhard and R. ScopignoRendering interior cultural heritage scenes using physically based rendering with outdoor environment maps is computationally expensive using ray tracing methods, and currently difficult for interactive applications without significant precomputation of lighting. In this paper, we present a novel approach to relight synthetic interior scenes by extending image-based lighting to generate fast high-quality interactive previews of these environments. Interior light probes are acquired from a real scene, then used to shoot light onto the virtual scene geometry to accelerate image synthesis by assuming the light sources shot act as the correct solution of light transport for that particular intersection point. We term this approach Image-Based Shooting. It is demonstrated in this paper with an approach inspired by Irradiance Cache Splatting. The methodology is well-suited for interior scenes in which light enters through narrow windows and doors, common at cultural heritage sites. Our implementation generates high-quality interactive preview renditions of these sites and can significantly aid documentation, 3D model validation and predictive rendering. The method can easily be integrated with existing cultural heritage reconstruction pipelines, especially ray tracing based renderers.Item Interaction in Distributed Virtual Environments(The Eurographics Association, 2005) Glencross, Mashhuda; Otaduy, Miguel; Chalmers, Alan; Ming Lin and Celine LoscosThis course will describe the main challenges faced when building engaging shared virtual environments supporting complex behaviour and interaction, and provide discussions on techniques that can be adopted to support some of these. In order to build such environments, it is necessary to combine high quality graphics, better modes of interaction, rich behavioural simulations and appropriate distribution strategies. After introducing the field of interaction and rich behaviour in collaborative virtual environments, we cover the main issues in three parts. First we look at techniques for improving the user s experience by using high-fidelity graphical rendering, and explore how this may be achieved in real-time through exploitation of features of the human visual perception system. We examine also how additional sensory modalities such as audio and haptic rendering may further improve this experience. Second we consider issues of distribution with an emphasis on avoiding potential pitfalls when distributing complex simulations together with an analysis of real network conditions, and the implications of these for distribution architectures that provide for shared haptic interaction. Finally we present the current state of the art of haptic interaction techniques. In particular the motivations for perceptually-inspired force models for haptic texture rendering, interaction between such models and GPU techniques for fast haptic texture rendering. The objective of this course is to give an introduction to the issues to consider when building highly engaging interactive shared virtual environments, and techniques to mediate complex haptic interaction with sophisticated 3D environments.Item Accurate Modelling of Roman Lamps in Conimbriga using High Dynamic Range(The Eurographics Association, 2008) Gonçalves, Alexandrino José Marques; Magalhães, LuÃs Gonzaga; Moura, João Paulo; Chalmers, Alan; Michael Ashley and Sorin Hermon and Alberto Proenca and Karina Rodriguez-EchavarriaThe Human Visual System has a remarkable ability to acquire colour and contrast of all the things that surround us. This is particularly evident in extreme lighting conditions such as bright light or dark environments. However, it is simply not possible to represent such a range of lighting on a typical display today. This is about to change. The field of High Dynamic Range (HDR) imagery allows us to capture and display the full range of human vision. The use of technologies in the preservation and dissemination of cultural heritage can play an important role in the representation and interpretation of our past legacy. A major field of application is virtual reconstructions of ancient historical environments. In this domain, the way we see such (reconstructed) environments is particularly important in order to establish a correct interpretation of that historical setting. In this paper we present a case study of the reconstruction of a Roman site. We generate HDR images of mosaics and frescoes from one of the most impressive monuments in the ruins of Conimbriga, Portugal, an ancient city of the Roman Empire. We show that the HDR viewing paradigm is well suited for archaeological interpretation, since its high contrast and chromaticity can disclose and present us an enhanced viewing experience, closer to how the artefacts may have been perceived in the past. To achieve the requisite level of precision, in addition to a precise geometric 3D model, it is crucial to integrate in the virtual simulation authentic physical data of the light used in the period under consideration. Thereby in order to create a realistic physical based environment we use in our lighting simulations real data obtained from Roman luminaries of that time.Item High Dynamic Range Display of Authentically Illuminated Byzantine Art from Cyprus(The Eurographics Association, 2007) Zanyi, Eva; Chrysanthou, Yiorgos; Bashford-Rogers, Tom; Chalmers, Alan; D. Arnold and F. Niccolucci and A. ChalmersHigh-fidelity computer reconstructions of cultural heritage sites attempt to create a faithful representation of the past physical environment. This includes modeling the scene to high precision, and accurately simulating the distribution of authentic light energy within the scene. This does not, however, ensure that the displayed image will have a high fidelity visual appearance due to the limited dynamic range of typical computer displays. Such displays only have a range of about two orders of magnitude between minimum and maximum luminance. A welldesigned cathode ray tube (CRT) monitor may do slightly better than this in a darkened room, but the maximum display luminance is only around 100 cd/m2, which does not even begin to approach natural daylight levels of approximately 105 cd/m2. Furthermore, their inability to display 'true black' means that standard displays also struggle to show low-light images accurately. In this paper we compare images of computer reconstructions of Byzantine art from Cyprus illuminated with simulated modern lighting and the candle light which was present in Byzantine times on both a traditional and a novel High Dynamic Range display.Item Photorealistic Augmented Reality(Eurographics Association, 2003) Gibson, Simon; Chalmers, AlanAugmenting real-world images with synthetic objects is becoming of increasing importance in both research and commercial applications, and encompasses aspects of fields such as mobile camera and display technology, computer graphics, image processing, computer vision and human perception. This tutorial presents an in-depth study into the techniques required to produce high fidelity augmented images at interactive rates, and will consider how the realism of the resulting images can be assessed and their fidelity quantified. The first half of the tutorial covers the methods we use to generate augmented images. We will show how commonly available digital cameras can be used to record scene data, and how computer graphics hardware can be used to generate visually realistic augmented images at interactive rates. Specific topics covered will include geometric and radiometric camera calibration, image-based reconstruction of scene geometry and illumination, hardware accelerated rendering of synthetic objects and shadows, and image compositing. The second half of the tutorial discusses in more detail what we are trying to achieve when generating augmented images, and how success can be measured and quantified. Methods for displaying augmented images will be discussed, and techniques for conducting psychophysical experiments to evaluating the visual quality of images will also be covered. Examples of augmented images and video sequences from a real-world interactive interior design application will be shown, and used to illustrate the different ideas and techniques introduced throughout the tutorial.Item Portals: Aiding Navigation in Virtual Museums(The Eurographics Association, 2003) Kotziampasis, Ioannis; Sidwell, Nathan; Chalmers, Alan; David Arnold and Alan Chalmers and Franco NiccolucciDistributed virtual environments offer an efficient way for a number of users to create complex 3D virtual worlds. However, navigation within these virtual environments can be significantly hampered by the lack of visibility between parts of the world, particularly when these parts are on different machines. This paper describes the use of portals to connect distributed virtual archaeological environments in such a way that the interconnected virtual environment will be visible from different machines in an efficient manner. A case study shows how a virtual museum can benefit from such a system.Item High Dynamic Range Imaging and Low Dynamic Range Expansion for Generating HDR Content(The Eurographics Association, 2009) Banterle, Francesco; Debattista, Kurt; Artusi, Alessandro; Pattanaik, Sumanta; Myszkowski, Karol; Ledda, Patrick; Bloj, Marina; Chalmers, Alan; M. Pauly and G. GreinerIn the last few years, researchers in the field of High Dynamic Range (HDR) Imaging have focused on providing tools for expanding Low Dynamic Range (LDR) content for the generation of HDR images due to the growing popularity of HDR in applications, such as photography and rendering via Image-Based Lighting, and the imminent arrival of HDR displays to the consumer market. LDR content expansion is required due to the lack of fast and reliable consumer level HDR capture for still images and videos. Furthermore, LDR content expansion, will allow the re-use of legacy LDR stills, videos and LDR applications created, over the last century and more, to be widely available. The use of certain LDR expansion methods, those that are based on the inversion of tone mapping operators, has made it possible to create novel compression algorithms that tackle the problem of the size of HDR content storage, which remains one of the major obstacles to be overcome for the adoption of HDR. These methods are used in conjunction with traditional LDR compression methods and can evolve accordingly. The goal of this report is to provide a comprehensive overview on HDR Imaging, and an in depth review on these emerging topics.