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Item Improving the digitization of shape and color of 3D artworks in a cluttered environment(The Eurographics Association, 2013) Bettio, Fabio; Gobbetti, Enrico; Merella, Emilio; Pintus, Ruggero; -We propose an approach for improving the digitization of shape and color of 3D artworks in a cluttered environment using 3D laser scanning and flash photography. In order to separate clutter from acquired material, semi-automated methods are employed to generate masks for segment the 2D range maps and the color photographs, removing unwanted 3D and color data prior to 3D integration. Sharp shadows generated by flash acquisition are trivially handled by this masking process, and color deviations introduced by the flash light are corrected at color blending time by taking into account the object geometry. The approach has been applied to, and evaluated on, a large scale acquisition campaign of the Mont'e Prama complex, an extraordinary collection of stone fragments from the Nuragic era, depicting larger-than-life archers, warriors, boxers, as well as small models of prehistoric nuraghe (cone-shaped stone towers). The acquisition campaign has covered 36 statues mounted on metallic supports, acquired at 0.25mm resolution, resulting in over 6200 range scans (over 1.3G valid samples) and 3426 10Mpixel photographs.Item Surface Light Field from Video Acquired in Uncontrolled Settings(The Eurographics Association, 2013) Palma, Gianpaolo; Desogus, Nicola; Cignoni, Paolo; Scopigno, Roberto; -This paper presents an algorithm for the estimation of the Surface Light Field using video sequences acquired moving the camera around the object. Unlike other state of the art methods, it does not require a uniform sampling density of the view directions, but it is able to build an approximation of the Surface Light Field starting from a biased video acquisition: dense along the camera path and completely missing in the other directions. The main idea is to separate the estimation of two components: the diffuse color, computed using statistical operations that allow the estimation of a rough approximation of the direction of the main light sources in the acquisition environment; the other residual Surface Light Field effects, modeled as linear combination of spherical functions. From qualitative and numerical evaluations, the final rendering results show a high fidelity and similarity with the input video frames, without ringing and banding effects.Item A Low-Cost Portable 3D Laser Scanning System with Aptness from Acquisition to Visualization(The Eurographics Association, 2013) Banerjee, Sumandeep; Biswas, Prabir Kumar; Bhowmick, Partha; Dutta, Somnath; -This paper presents the design perspectives of a low-cost portable 3D laser scanning mechanism. The hardware is simple in design, easy to fabricate, and costs much less compared to the cheapest ones available in the market. Moreover, it is noninvasive and able to generate high-quality data sets. We present the complete design pipeline and discuss how to implement and put together the most recent algorithms. We propose this design for its wide applications to virtual reality simulation, 3D modeling, digitization of archaeological artifacts, automated defect inspection, object recognition etc.Item Global refinement of image-to-geometry registration for color projection on 3D models(The Eurographics Association, 2013) Dellepiane, Matteo; Scopigno, Roberto; -The management, processing and visualization of color information is a critical subject in the context of the acquisition and visualization of real objects. Especially in the context of Cultural Heritage, artifacts are so complex or hard-to-handle that the appearance information has to be extracted from a set of images. The images usually have to be registered to the 3D model of the objects, in order to transfer the needed information. Hence, the problem of image-to-geometry registration has been thoroughly studied by the Computer Graphics and Computer Vision community. Several methods have been proposed, but a fully automatic and generic solution is still missing. Moreover, small misalignments often lead to visible artifacts in the final colored 3D models. In this paper, we propose a method to refine the alignment of a group of images which has been already registered to a 3D model. Taking advantage of the overlapping among the images, and applying a statistical global method based on Mutual Information, the registration error is distributed among all the elements of the dataset. Hence, the quality of color projection is improved, especially when dealing with small details. The method was tested on a number of heterogeneous Cultural Heritage objects, bringing to a visible improvement in the rendering quality. The method is fully automatic, and it does not need powerful hardware or long processing time. Hence, it represents a valid solution for a wide application on CH artifacts.Item On-the-fly automatic alignment and global registration of free path collected 3D scans(The Eurographics Association, 2013) Signoroni, Alberto; Bonarrigo, Francesco; Pezzotti, Nicola; -We present a complete geometry processing pipeline for multiple 3D scans alignment, composed by a fast, automated feature-based coarse alignment and an efficient global registration, with the aim to enable high-quality and high-throughput cultural heritage digitization. Salient features of our pipeline consist in the capability to provide low-latency, on-the-fly coarse alignment regardless to the number of scans, the capacity to handle interruptions of a continuous acquisition path, as well as an improved implementation of a robust state-of-the-art global alignment technique.Item Faithful, Compact and Complete Digitization of Cultural Heritage using a Full-Spherical Scanner(The Eurographics Association, 2013) Nöll, Tobias; Köhler, Johannes; Reis, Gerd; Stricker, Didier; -Effective documentation and display of ancient objects is an essential task in the field of cultural heritage conservation. Digitization plays an important role for the process of creating, preserving and accessing objects in digital space. Up to the present day, industrial scanners are used for this task that focus mainly on the detailed reconstruction of the object's geometry only. However, important for a faithful digital presentation of the object is in particular the appearance information, i.e. a description of the used materials and how they interact with incident light. Using the worlds first full-spherical scanner, we propose a user friendly reconstruction process that is specifically tailored to the needs for digitizing and representing cultural heritage artifacts. More precisely, our hardware specifically addresses the problem that invaluable or fragile artifacts may not be turned over during acquisition. Nevertheless, we can digitize the object completely including its bottom. Further, by integrating appearance information into our digitization we achieve a far more faithful digital replica with a quality comparable to a real picture of the object. But in contrast to a static picture, our representation allows to interactively change the viewing and lighting directions freely. In addition, the results are very memory efficient, consuming only several MB per scanned object and hence are suited to be accessed and visualized interactively in a web browser. In cooperation with museums and a private collector, we digitized several cultural heritage artifacts in order to demonstrate the feasibility of the proposed process.