DH2013 - Track 1

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https://diglib.eg.org/handle/10.2312/12322

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Multi-scalar 3D digitization of Cultural Heritage using a low-cost integrated approach
(The Eurographics Association, 2013) Manferdini, Anna Maria; Russo, Michele; -
In the architectural survey field, one of the main aspects to consider during a 3D digitization is the multi-scalar geometrical complexity of the artifact to acquire, besides other fundamental factors connected with the different aims of communication. Since the widespread of range-sensors has provided extremely versatile instruments able to easily acquire huge amount of data that can be processed for different uses and users and changing communication aims, the possibility to survey and restore high-quality 3D multi-resolution models has become an urgent need. Despite these developments, these technologies are still very expensive, need expertise and present persistent bottlenecks both in the reverse modeling process and in time consuming. In order to overcome these critical aspects and taking advantage of recent improvements of automated image-based technologies based on the Structure from Motion approach, this contribution presents some first results of investigations on the reliability of these low-cost technologies for the 3D digitization of Cultural Heritage. One of the main aims of these investigations rely on developing a procedure that could ease the work of surveyors called to represent artifacts at an architectural scale using fast and low-cost technologies. 3D models derived using the selected low-cost image-based technologies were compared among each other and with a 3D laser scanner gold standard acquisition. These investigations led to qualitative and quantitative evaluations and to considerations on times and skills required by all tested technologies. Strengths and weaknesses are highlighted, suggesting the best solution with respect to the optimization of all considered aspects. Finally, integration of different technologies are presented, as it represents the best solution in multi-scalar contexts.
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.
A Methodology for Updating 3D Solid Models of Complex Monumental Structures Based on Local Point-based Meshes
(The Eurographics Association, 2013) Zvietcovich, Fernando; Castaneda, Benjamin; Perucchio, Renato; Morales, Ricardo; Uceda, Santiago; -
Structural changes introduced during the life of monuments contribute to produce complex geometrical configurations that cannot be properly represented in standard solid modeling systems designed for current engineering applications such as finite element analysis (FEA). Likewise, point-based 3D meshes laser-scanner or photogrammetric , although capable of constructing detailed representation of surfaces, cannot be used for direct application in structural analysis because they do not produce complete and unambiguous solid models. To tackle this issue, we merged these two approaches into a unified methodology capable of updating a 3D solid model, representing the entire monument as reconstructed in its presumed original configuration, with information from a 3D mesh model containing a detailed geometrical description of the recent structural state of a specific sector of the same monument. The methodology is based on a series of functions that operate in the Mesh and Solid Modeling Space. The mesh model is aligned via 3D registration and, subsequently, segmented for its conversion to a solid model. Finally, this solid updates the solid representation of the entire monument via Boolean operations. We test the procedure on the Main Platform of the Huaca de la Luna, Trujillo, Peru, one of the most important massive earthen structures of the Moche civilization. Solid models are defined in AutoCAD while 3D meshes are constructed via the photogrammetric program Agisoft PhotoScan. The results indicate that the proposed methodology is effective at transferring complex geometrical and topological features from the mesh to the solid modeling space. The updated solid model can be represented and visualized in any standard CAD software, and utilized for FEA and augmented reality applications.
Replicating perishable artefacts. A project for analysis and exhibition of Early Medieval objects from the Byzantine village at Scorpo (Supersano, Italy)
(The Eurographics Association, 2013) Bandiera, Adriana; Arthur, Paul; Imperiale, Marco Leo; Maffezzoli, Alfonso; Frigione, Mariaenrica; Montagna, Francesco; Signore, Grazia Maria; -
Artefacts found in an archaeological excavation are sometimes made of perishable or fragile material like wood, iron, or leather. These present obvious conservation problems. This is the case of various artefacts from the Byzantine village of Scorpo (Supersano, southern Italy) that has been the object of excavations by archaeologists from the University of Salento (Italy) since 1999. In 2007 a number of wooden objects were discovered in a well, while in 2012 a hoard of ferrous objects was found near a drystone wall that perhaps enclosed the settlement. Given the highly fragile and perishable nature of the objects, the questions arise as to how to study these artefacts, preserve them for the future and display them to the public. In this paper we will illustrate the methodology developed at the University of Salento to give an answer to all these questions and we will describe the entire process ranging from the discovery of the artefacts, to their 3D digital acquisition and modeling, the eventual digital restoration, the realization of one or more physical copies using a rapid prototyping apparatus (RP), to their display in a museum. Digital models of artefacts and ancient contexts are increasingly used in museums in order to improve communication, also for the disabled. Furthermore, the resin replica of an object, created from its digital 3D model, can also be useful for its preservation and fruition, especially if it is fragile or in poor condition.
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.
Feature-based automatic 3D registration for cultural heritage applications
(The Eurographics Association, 2013) Tombari, Federico; Remondino, Fabio; -
This paper presents a review of the state-of-the-art techniques in the field of 3D invariant features for the automatic registration of point clouds and 3D meshes. The paper proposes also a multi-stage 3D registration pipeline implemented using the PCL libraries. Experiments are carried out on datasets related to heritage scenarios and addressing large-scale outdoor data acquisitions as well as small objects.
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.
3D documentation of Cultural Heritage artefacts: from data acquisition to virtual conservation and restoration
(The Eurographics Association, 2013) Athanasiou, Eleni; Faka, Marina; Hermon, Sorin; Vassallo, Valentina; Yakoupi, Kyriaki; -
This paper focuses on the development of a procedure for 3D documentation of Cultural Heritage assets and describes all the steps from the 3D data acquisition of the real object, the post processing the raw data and finally the digital recording, documentation and virtual preservation of the 3D data. It will also describe the experiences, carried out during the digital process, of some virtual restoration cases.
Design and implement a reality-based 3D digitisation and modelling project
(The Eurographics Association, 2013) Remondino, Fabio; Menna, Fabio; Koutsoudis, Anestis; Chamzas, Christos; El-Hakim, Sabry; -
3D digitisation denotes the process of describing parts of our physical world through finite measurements and representations that can be processed and visualised with a compute r system. Reality-based 3D digiti sation is essential for the documentation, conservation and preservation of our Cultural Heritage. This article composes a critical review of the digitisation pipeline, ranging from sensor selection and planning to data acquisition, processing and visualisation.
Reverse Engineering of Scale Models Using Dataflow Programming: Application to the fortification of plans-reliefs
(The Eurographics Association, 2013) Jacquot, Kevin; Chevrier, Christine; Gilles, Halin; -
Despite the progress in three-dimensional scanning, some architectural artifacts remain a digitizing challenge. Scale models and more especially the plans-reliefs of Louis XIV of France have specific characteristics such as size, scale, number, etc. A knowledge-based modeling approach is developed to address the limitations of digitizing tools. Our study deals with the fortified areas of the scale models. Bastioned fortification works extend over wide areas but they are built according to design rules. Once studied and organized, fortification knowledge has been used to create a library of parametric components. Implemented in Grasshopper, the components were manually adjusted to different practical cases. The library was then validated and we are now focusing on the automation of the adjustments of the components. Thereupon a reverse-engineering approach has been set up. Semantic segmentation algorithms have been defined and implemented in Grasshopper to automatically extract fortification features from 3D surveys based on the knowledge of fortification design rules. Along with the three-dimensional modeling of fortification, an automatic reconstruction of the city parts of the scale models is underway. Both these studies are part of a project aimed at valorizing and diffusing a very unique cultural heritage collection. As such, knowledge models are precious assets both the digitizing and the semantic enhancements of the final application.
Characterization of European Lacquers by terahertz (THz) reflectometric imaging
(The Eurographics Association, 2013) Dandolo, Corinna Ludovica Koch; Jepsen, Peter Uhd; -
In this study a European lacquerware replica has been investigated by terahertz (THz) reflectometric imaging. The inspected lacquerware is a wooden panel covered by multiple complex layers of lacquers and plaster. Utilizing pulsed Terahertz Time-Domain Imaging (THz-TDI) in reflection mode, we observe non-invasively buried layers of the lacquerware replica, including the internal structure of the wooden panel itself. We find that non-invasive terahertz reflectometric imaging analysis of lacquerware is can provide conservators with important information about the condition of the compositional layers, potentially aiding in the development of appropriate conservation treatments. With the same technique we have performed a surface material mapping. The material distribution has been enhanced through reflected THz composite RGB false color rendering, where RGB mapping allows distinction between different materials and textures on the surface of the lacquerware. The contrast between different textures is enabled by wavelength-dependent scattering from the surface, as well as differences in the composition of the surface layer.
Temporal Terrestrial Laser Scanning to Visualize the Archaeological Excavation Process
(The Eurographics Association, 2013) Srour, David; Richter, Ashley; Levy, Thomas; Kuester, Falko; -
Archaeology is a destructive science. Photographs and videos preserve some aspects of the sequence of events inherent within the archaeological excavation process, but cannot replicate the spatiality and detail of the downward progression of the digging entailed through excavation. Time lapse sequences of properly adapted and employed terrestrial laser scanning to create a temporal sequence of point clouds of the archaeological methodologies can, however, serve as an innovative step towards accurate documentation of crucial data for future archaeologists interested in the site. Over the course of the National Science Foundation Integrative Graduate Education and Research Traineeship funded Sediment Intervals and Site Deformation Processes: Exploring Time Lapse Laser Scanning Capabilities and Methodologies for Archaeology, temporal scanning was tested on the beaches of San Diego to establish a baseline capability for data capture. Subsequently, the methodologies for data collection were utilized as a part of the excavation workflow at the University of California, San Diego's Edom Lowlands Regional Archaeological Project's excavation of a Roman era section of tell Khirbat Faynan in southern Jordan. With the data collected from the excavation as the impetus for new system development, original visualization processing designed with the archaeological problems and end-goals in mind is being created at the University of California, San Diego Center of Interdisciplinary Science for Art, Architecture, and Archaeology in order to meaningful display the shifting data sets in real time and exhibit not just the archaeological data, but the archaeological process.
Quick textured mesh generation for massive 3D digitization of museum artifacts
(The Eurographics Association, 2013) Gonizzi, Sara; Micoli, Laura L.; Guidi, Gabriele; -
The goal of the "3D Icons" European Project, is to provide Europeana with accurate 3D models of Cultural Heritage artifacts. The purpose of this paper is to describe the specific optimized processing pipeline that has been set-up for digitizing a significant part of the Civic Archaeological Museum in Milan (Italy). Many technical and logistic issues for capturing 3D models in a Museum environment are addressed. In such framework the main problem is generating a good result by the technical point of view, minimizing the impact on the usual Museum activity during 3D capture operations, while shortening the processing time to the minimal allowed by the different applicable techniques. This condition led to precise choices related to the 3D acquisition techniques to be used (SfM), and the related data processing. This paper illustrates the aforementioned systematic aspects through three practical examples, showing good practices for image capturing and some 3D processing optimizations that allowed to speed the 3D models production at a level compliant to the final goal of more than 500 models in 36 months.
Cutting-edge technologies for the survey and documentation of cultural heritage: the case study of the architectural-archaeological area of Aruch in Armenia
(The Eurographics Association, 2013) Versaci, Antonella; Cardaci, Alessio; -
One of the most important finalities of survey is the architecture's comprehension. To the end of cultural heritage conservation, it is furthermore necessary to communicate the acquired knowledge. In the recent years, this need has resulted in a radical change in cataloging and digitization systems, as well as in telematics networking. Moreover, the use of 3D laser scanner has transformed not only the approaches related to metrics data acquisition and graphic rendering but has also afforded the opportunity to share important information on the web. This paper focuses on the usefulness of state-of-the-art technologies for documentation, presenting a case study related to the architectural-archeological area of Aruch in Armenia.
Measuring Changes in Cultural Heritage Objects with Reflectance Transform Imaging
(The Eurographics Association, 2013) Manfredi, Marcello; Williamson, Greg; Kronkright, Dale; Doehne, Eric; Bearman, Gregory; Jacobs, Megan; Marengo, Emilio; -
Sites and objects of cultural heritage from art to ancient inscriptions to ruins are under constant attack by time and the environment. While much is known about how material components change from laboratory-based artificial aging, very little is known about the process or rates of change of actual objects and sites in situ. Reflectance Transformation Imaging (RTI) is a quantitative method that captures surface normals. In our case, it provides detailed information on the geometry of the object surface. We show that RTI can be quantified for use as a method for measuring change in cultural heritage objects. The past decade has seen the rapid evolution and application of computational photography methods to document important works of human heritage, from art and architecture to archives and archaeology. The next logical step involves defining just how reproducible and precise these methods can be to use them to measure rates of change for important works of cultural heritage. The need is to move to calibrated, quantitative image datasets for reproducible imaging. We measure the precision of computed surface normals, which define the basic repeatability of RTI. Our results show that the average included solid angle for RTI sensitivity fitted to the Hemispherical Harmonics (HSH) polynomial function is 0.003 steradians (3 sigma), while the older Polynomial texture map (PTM) method is much less sensitive (0.5 steradians). The absolute sensitivity of the method is the minimum variation of the normal that can be statistically considered a change of the object. It is calculated considering the average value of the normal of each single pixel. The solid angle of the cone of variation represents the statistical limit (3 *s). Analysis of multiple RTI data sets from objects that have changed between image capture sessions results in a map of change that can easily be evaluated by conservators.
Realistic Virtual Reproductions. Image-based modelling of geometry and appearance
(The Eurographics Association, 2013) Martos, Antonio; Ruiz, Bernardino; -
Existing technologies for contact-less 3D scanning and Image Based Modelling (IBM) methods are being extensively used nowadays to digitize cultural heritage elements. With a convenient degree of automation these methods can properly capture and reproduce shape and basic colour textures. However, there is usually a quite evident lack of fidelity in the resulting appearance of the virtual reproductions when compared with the original items. Even when properly photo-textured, the reproduced surfaces often resemble either plaster or plastic, regardless of the properties of the original materials. What is neither captured nor modelled is the natural dynamic response of the actual materials with respect to changes in observation angle and/or the lighting arrangement. The methodology introduced in this paper tries to improve the three-dimensional digitalization and visualization of cultural heritage elements, by extending the present capabilities of IBM with additional capture and modelling of surface appearance. We show that it is possible to automatically reproduce realistic-looking virtual objects and scenes, even with photographs taken with an uncalibrated single moving camera and while under uncontrolled and intentionally variable lighting conditions. This is achieved not only by reconstructing the shape and projecting colour texture maps from photographs, but also modelling and mapping the apparent optical response of the surfaces to light changes, while also determining the variable distribution of environmental illumination of the original scene. This novel approach integrates Physically Based Render (PBR) concepts in a processing loop that combines capture and visualization. Using the information contained in different photographs, where the appearance of the object surface changes with environmental light variations, we show that it is possible to enhance the information contained in the usual colour texture maps with additional layers. This enables the reproduc- ion of finer details of surface normals and relief, as well as effective approximations of the Bi-directional Reflectance Distribution Function (BRDF). The appearance of the surfaces can then be reproduced with a dedicated render engine providing unusual levels of detail and realism due to enriched multi-layer texture maps and custom shading functions. This methodology will be introduced with a real case-study, to illustrate its practical applicability and flexibility; The virtual reproduction of the Lady of Elche was performed only from archived photographs taken at the museum for different documentation purposes, using uncalibrated optics and an uncontrolled studio light arrangement. We discuss the capture on larger architectural elements as well, with uncontrolled (yet still variable) illumination in outdoor environments and challenging items with difficult to capture surfaces such as the brass sculpture of La Regenta, where proper reproduction of surface reflection and environmental lights are fundamental steps to provide a good visualization experience. These cases will show the feasibility of working with field calibration and initial approximations for the camera model and light-maps, addressing thus the flexibility required for practical field documentation in museum environments or outdoors. The potential for diffusion will be shown with the use of open source software tools for enhanced visualization. The presented capture methods are integrated with the specific adaptation of open-source GPU-based (Graphics Processing Unit) render engines to produce two flavours of 3D inspection/visualization tools with proper relighting capabilities, able to reveal very subtle details: A quasi-real time realistic engine (Blender Cycles), which is also the basis for the capture process and is focused on realistic reproduction, and a real-time version based on customized pixel shaders, for the real-time visualization of lightweight models on web browsers and other interac
Low-cost mobile system for multispectral cultural heritage data acquisition
(The Eurographics Association, 2013) Blazek, Jan; Soukup, Jindrich; Tichý, Tomás; Zitova, Barbara; Hradilová, Janka; Flusser, Jan; -
In the paper we propose an alternative approach to the multispectral data acquisition of the cultural heritage artifacts. The demonstrated solution is mobile, affordable, and consists only of commercial off-the-shelf products. It could be used for the data acquisition in-situ without limitations. It was designed for multispectral scanning of cultural heritage artifacts for their first analysis, for multimedia presentations dedicated to public, and, of course, for art conservation studies. The presented solution contains next to the hardware part as well the description of pre-analysis step two alternative ways of the photometric calibration to ensure the anticipated precision. The applicability of the framework was demonstrated on the case study, the preliminary spectral analysis. The proposed methodology is successfully used in the art restoration practice.
GNSS role in planning and conductance of terrain archaeological survey: technical aspects and methodology
(The Eurographics Association, 2013) Stamenov, Stefan; Naydenova, Vanya; -
The purpose of the present paper is to present the technical aspects and the methodological framework of applying non-destructive methods and technologies for planning and conductance of terrain archaeological survey. The remote sensing methods together with the GNSS and geoinformation technologies play an important role in the terrain survey. The proposed approach is focused on the technical aspects of applying GNSS technologies in the field work. This approach was applied on the Early-Medieval archaeological object Kabiyuk, located in Northeast Bulgaria, announced as a National Historical and Archaeological Reserve in 2012. Kabiyuk is one of the main archaeological sites connected with the First Bulgarian Kingdom, whose earthen rampart is at second place after the fortification of the First Bulgarian Capital Pliska. The methodological framework for terrain survey includes four main stages planning of the terrain archaeological survey; preliminarily survey of the archaeological site; conductance of the terrain survey and GNSS measurements and post-processing of the recorded data and collected information. During the planning of the terrain archaeological survey, information from remote sensing data (satellite images and aerial photos) was used to define the areas without built-up lands or thick forests, waters bodies. In the second stage a preliminarily survey were conducted during which areas without vegetation cover were defined on which archeological surveys will be carried out. The terrain survey was conducted using preliminarily generated digital grid, which was applied for the first time in the investigation of the First Bulgarian capital Pliska by the same team. A GNSS receiver with high accuracy is required for navigation according to the digital grid and for registration the discovered new potential archaeological objects, and as well as for detailed archaeological mapping.
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.
Digital Production of Traditional Costumes
(The Eurographics Association, 2013) Kang, Yeonkyung; Wu, Sehee; Ko, Young-A; Martin, Kathi; Ko, Hyeong-Seok; -
The role of the museum has changed from a "onesided information delivery" system focusing on exhibition and education to ''community as culture''. Creating richly detailed digitized reproductions of museum holdings can stimulate the social media dialogue between museum and visitor. The purpose of this study is to determine the feasibility of reproducing traditional costumes using digital technology. For this experiment, we selected a woman's robe and a man's ensemble of the Rococo era of the 18th century. Using historical reference material we first analyzed the design features of the silhouette, and the fabrics, hairdos and accessories of the period. This paper details the application of 3D technologies, DC Suite and Maya Qualoth, to reconstruct them.

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