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Item Radiometric Characterization of Spectral Imaging for Textual Pigment Identification(The Eurographics Association, 2011) Kim, Min H.; Rushmeier, Holly; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolDigital imaging of cultural heritage artifacts has become a standard practice. Typically, standard commercial cameras, often commodity rather than scientific grade cameras, are used for this purpose. Commercial cameras are optimized for plausible visual reproduction of a physical scene with respect to trichromatic human vision. However, visual reproduction is just one application of digital images in heritage. In this paper, we discuss the selection and characterization of an alternative imaging system that can be used for the physical analysis of artifacts as well as visually reproducing their appearance. The hardware and method we describe offers a middle ground between the low cost and ease of commodity cameras and the high cost and complexity of hyperspectral imaging systems. We describe the selection of a system, a protocol for characterizing the system and provide a case study using the system in the physical analysis of a medieval manuscript.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 Preserving the Khmer Smile: Classifying and Restoring the Faces of Bayon(The Eurographics Association, 2011) Lu, Min; Zheng, Bo; Takamatsu, Jun; Nishino, Ko; Ikeuchi, Katsushi; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolThe Bayon temple is known for its numerous massive stone faces with serene smiles, often referred to as the 'Khmer Smile.' Many of these sculptures are, however, only partially preserved, making it difficult to see the original appearance of these faces. To restore the Bayon faces, we propose a novel method that builds upon the matrix recovery theory. The method achieves accurate restoration by adopting a two-step shape recovery strategy. Rough restoration and clustering processes are first carried out using the entire database to group similar samples together. Then refined restoration using high resolution data is executed in each cluster to restore higher details while retaining the characteristics of each face. Experimental results demonstrate the effectiveness of our proposed method.Item Virtual Heritage in the Cloud: New Perspectives for the Virtual Museum of Bologna(The Eurographics Association, 2011) Lercari, Nicola; Toffalori, Elena; Spigarolo, M.; Onsurez, L.; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolThis paper focuses on the integration of Cloud computing tools and user-generated content into an online cultural virtual environment. Our investigation aimed to clarify whether the Metaverse can be used as a spatial interface for aggregation and synestetic visualization of heterogeneous cultural data distributed in the Cloud. The case study we adopted is Nu.M.E. 2010 a virtual reconstruction of Piazza di Porta Ravegnana, a crucial area of late medieval Bologna (Italy), published on the platform Second Life (SL). A newfound awareness and appreciation for the new epistemic scenario introduced by Cloud computing and virtualization techniques has raised the following methodological questions: can Cloud computing help optimize the communication strategy and educational effectiveness of cultural data online? Can historical research and cultural data interpretation benefit from collaborative annotation and user-generated content? The described application entailed the use within SL of some of the most popular virtualization services: Google Maps, Panoramio, Google Docs, and Google Warehouse. The results of our testing activity suggest that Cloud services currently available are in fact useful tools for reshaping an online virtual space into an effective collaborative place, allowing users to share content, take an active part in the interpretation process and, most importantly, to provide valid feedback for cultural reception analysis.Item WebGL-based Streaming and Presentation Framework for Bidirectional Texture Functions(The Eurographics Association, 2011) Schwartz, Christopher; Ruiters, Roland; Weinmann, Michael; Klein, Reinhard; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolMuseums and Cultural Heritage institutions have a growing interest in presenting their collections to a broader community via the Internet. The photo-realistic presentation of interactively inspectable digital 3D replicas of artifacts is one of the most challenging problems in this field. For this purpose, we seek not only a 3D geometry but also a powerful material representation capable of reproducing the full visual appeal of an object. In this paper, we propose a WebGL-based presentation framework in which reflectance information is represented via Bidirectional Texture Functions. Our approach works out-of-the-box in modern web browsers and allows for the progressive transmission and interactive rendering of digitized artifacts consisting of 3D geometry and reflectance information. We handle the huge amount of data needed for this representation by employing a novel progressive streaming approach for BTFs which allows for the smooth interactive inspection of a steadily improving version during the download.Item The Digital 3D Survey as Standard Documentation of the Archaeological Stratigraphy(The Eurographics Association, 2011) Fiorini, Andrea; Urcia, Alberto; Archetti, Valentina; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolIn this contribution we describe tools and methods used to perform three-dimensional photogrammetric survey of different archaeological contexts. In particular, we studied in depth some aspects: swiftness (of the proceeding), accuracy (of the measurement), informative contents (of the registration) and cost (of the instruments). Considering these factors we propose some solutions for the integration of photomodelling and stereophotogrammetry within the current standards of archaeological documentation. The first part will show three-dimensional photomodelling examples of walls stratigraphy and structural elements. Then follows the comparative analysis of two different technique of survey for the documentation of the same archaeological context: the direct detection and the stereophotogrammetric one of a burial. The second part discusses the first results of an experiment still in progress: the documentation of all the contexts identified during an archaeological excavation by stereo-detection. The contribution closes with an experience of photogrammetric survey of petroglyphs.Item VSim: Real-time Visualization of 3D Digital Humanities Content for Education and Collaboration(The Eurographics Association, 2011) Poyart, Eduardo; Snyder, Lisa; Friedman, Scott; Faloutsos, Petros; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolThis paper presents VSim, a framework for the visualization of 3D architectural and archeological models. VSim's design focuses on educational use and scholarly collaboration, an approach that is not commonly found in existing commercial software. Two different camera control modes address a variety of scenarios, and a novel smoothing method allows fluid camera movement. VSim includes the ability to create and display narratives within the virtual environment and to add spatially localized multimedia resources. A new way to associate these resources with points and orientations in space is also introduced.Item Fast and Robust Semi-Automatic Registration of Photographs to 3D Geometry(The Eurographics Association, 2011) Pintus, Ruggero; Gobbetti, Enrico; Combet, Roberto; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolWe present a simple, fast and robust technique for semi-automatic 2D-3D registration capable to align a large set of unordered images to a massive point cloud with minimal human effort. Our method converts the hard to solve image-to-geometry registration problem in a Structure-from-Motion (SfM) plus a 3D-3D registration problem. We exploit a SfM framework that, starting just from the unordered image collection, computes an estimate of camera parameters and a sparse 3D geometry deriving from matched image features. We then coarsely register this model to the given 3D geometry by estimating a global scale and absolute orientation using minimal manual intervention. A specialized sparse bundle adjustment (SBA) step, exploiting the correspondence between the model deriving from image features and the fine input 3D geometry, is then used to refine intrinsic and extrinsic parameters of each camera. Output data is suitable for photo blending frameworks to produce seamless colored models. The effectiveness of the method is demonstrated on a series of real-world 3D/2D Cultural Heritage datasets.Item Integrated High-Quality Acquisition of Geometry and Appearance for Cultural Heritage(The Eurographics Association, 2011) Schwartz, Christopher; Weinmann, Michael; Ruiters, Roland; Klein, Reinhard; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolCurrent research trends demonstrate that, for a wide range of applications in cultural heritage, 3D shape acquisition alone is not sufficient. To generate a digital replica of a real world object the digitized geometric models have to be complemented with information pertaining to optical properties of the object surface. We therefore propose an integrated system for acquiring both the 3D shape and reflectance properties necessary for obtaining a photo-realistic digital replica. The proposed method is suitable for the digitization of objects showing the complex reflectance behavior, for example specularities and meso-scale interreflections, often encountered in the field of cultural heritage. We demonstrate the performance of our system with four challenging examples. By using Bidirectional Texture Functions, our structured light based approach is able to achieve good geometric precision while preserving tiny details such as scratches and engravings.Item Real-time Rendering of Massive Unstructured Raw Point Clouds using Screen-space Operators(The Eurographics Association, 2011) Pintus, Ruggero; Gobbetti, Enrico; Agus, Marco; Franco Niccolucci and Matteo Dellepiane and Sebastian Pena Serna and Holly Rushmeier and Luc Van GoolNowadays, 3D acquisition devices allow us to capture the geometry of huge Cultural Heritage (CH) sites, historical buildings and urban environments. We present a scalable real-time method to render this kind of models without requiring lengthy preprocessing. The method does not make any assumptions about sampling density or availability of normal vectors for the points. On a frame-by-frame basis, our GPU accelerated renderer computes point cloud visibility, fills and filters the sparse depth map to generate a continuous surface representation of the point cloud, and provides a screen-space shading term to effectively convey shape features. The technique is applicable to all rendering pipelines capable of projecting points to the frame buffer. To deal with extremely massive models, we integrate it within a multi-resolution out-of-core real-time rendering framework with small pre-computation times. Its effectiveness is demonstrated on a series of massive unstructured real-world Cultural Heritage datasets. The small precomputation times and the low memory requirements make the method suitable for quick onsite visualizations during scan campaigns.