3DSSE – A 3D Scene Search Engine: Exploring 3D scenes using keywords

The evolution of real time 3D graphics technologies in combination with high bandwidth Internet connections and modern Web browsers enable users to explore complex 3D scenes. As a rule, a virtual visitor has to manually explore the geometrically complex 3D model in order to discover points of interest. This manual exploration is a time consuming process that, in some cases, can be assisted by sets of predefined points of interest. In this paper, we propose the annotation of 3D scenes in order to equip the user with a text based 3D scene search engine. The search engine provides a query mechanism that unburdens the user from the time consuming process of manually exploring vast 3D scenes. It responds to queries by exploiting the metadata of each 3D model and returns textual and visual information along with a group of links that correspond to relative points of interest within the 3D scene. The search engine allows the virtual visitor to automatically be transferred to a specific point of interest. We have built a Web accessible prototype system that is able to handle queries related to historical data, topological relationships and architectural properties of buildings. A number of 3D reconstructions covering urban areas of cultural importance located in Northern Greece have been annotated and used in the search engine as case studies. The prototype system is based on open source technologies and on a hybrid metadata schema that is derived from the MIDAS Heritage and MACE schemas.     

Automatic registration of large range datasets with spin-images

Terrestrial laser scanning technique has represented one of the more advances occurred in the last years in the field of data acquisition. Time-of-Flight (TOF) systems provide a fast and reliable tool to measure millions of 3D points allowing a very effective and dense measurement of the surface geometry. Nowadays, the generation of high quality 3D models is a practice applied to different kind of objects: small or medium size artworks, parts of human body, cars, buildings, civil infrastructures (like dams, bridges, plants, etc.) and whole archaeological sites as well. In most cases, in order to capture the whole object geometry a number of single scans need to be acquired from different positions and then stitched together (i.e. registered each other) to generate the full 3D model. The automatization of the registration of multiple scans acquired from a terrestrial laser scanner (TLS) still represents a very attractive research field. The chance to automatically align several point clouds would reduce processing costs in terms of time and human resources. In addition it would allow even non-specialist users to produce 3D models with good quality. This paper contributes to this research area by presenting a method for the automatic registration of very dense point clouds acquired by TLS systems. The proposed solution is an extension to large datasets of an automatic range data registration procedure we developed a few years ago for the modelling of point clouds acquired with close-range laser scanners. Such procedure, based on the spin-images (SIs) algorithm, has been then improved with the introduction of a multi-resolution method that generates a pyramid of spin-images in order to speed up the matching between adjacent scans. The results we present show that this method can be successfully applied for the automatic registration of high density laser scans of complex and large structures of Cultural Heritage.     

AI and virtual crowds: Populating the Colosseum

Computer technologies and digital recreations have been widely used in the field of Cultural Heritage in the past decade. However, most of the effort has concentrated in accurate data gathering and geometrical representation of buildings and sites. Only very recently, works are starting to go beyond that approach by including digital people. The impressive development of computer graphics techniques and computing power, makes now possible the creation and management of virtual environments where a big number of virtual creatures interact and behave in a smart manner.In this paper we present a novel use of virtual crowds for Cultural Heritage: we use them to predict behaviors, or to help scholars draw more educated conclusions on unknown matters. We specifically present a case study based on an artificial intelligence crowd simulation which is being used by scholars to study the ergonomics of the Roman Colosseum: it was formerly believed to be an excellent people-mover, but currently that belief is seriously questioned, as potential bottlenecks seem to have been detected.     

Decay regions segmentation from color images of ancient monuments using fast marching method

This work faces the problem of detecting decay zones from color images of stone materials. In Cultural Heritage, the extraction of degradation regions from images of ancient monuments represents an important step forward in studying and analyzing the state of preservation of historical buildings. Generally the decay diagnosis is provided by “naked eye” analysis done by expert scientists “walking around” the artifact and recording the conservation state of each individual element they observe. In addition to this kind of investigation, the application of an image segmentation strategy to color images of stony materials can be used in order to extract regions characterized by a visible chromatic alteration, changes in color, for example, as oxidation or concretion. This paper features a color image segmentation approach founded on the fast marching numerical method. We have applied this technique for its possibility to work locally, that is, only the contour of the region under study is processed. In addition to this method, we present a global approach, that is, the possibility to extract decay regions from the entire image; these regions are spatially disconnected but with similar colorimeter value. The main aim of the present work is to provide a tool that helps the expert to contour the degraded regions. In this sense even if the results of the proposed procedure depend on the expert evaluation, the approach can be a contribution to improve the efficiency of the boundary detection process. The study case concerns the impressive remains of the Roman Theatre in the city of Aosta (Italy). In the image segmentation process the color space L*a*b* is utilized.     

Cartographic heritage: Toward unconventional methods for quantitative analysis of pre-geodetic maps

Historical cartography all over the world is a fundamental part of Cultural Heritage, and it needs to be preserved from damage of its analogical support due to ageing. Regeneration of ancient cartography in digital form is an interesting way not only to preserve historical cartographic documents as Cultural Heritage, but also to allow new chances of understanding and using the historical information they record. In such a way, modern digital techniques, in particular study of map deformations and map georeferencing, help in metric analysis of ancient cartography, and at last they appear to be useful for researchers to derive historical information for their studies, for example related to urban development or to geomorphological and environmental topics. The present research would give an example of the usefulness of the digital regeneration of ancient cartography, but also an example of possible difficulties in correctly interpreting information preserved in historical cartography, especially the pre-geodetic one. The study subject consists in three contemporaneous pre-geodetic maps (late 16th century) from the ancient Po river delta area (Italy), by means of which a geometrically correct representation of those parts of the landscape, not preserved today because of sea erosion, was tried. In fact, standard georeferencing methods, that use reference control points to compare historical cartography with the present one, in this specific case demonstrated to be not successful in describing the real location of disappeared landscape details with an adequate level of accuracy. For these reasons, in order to define which map among the others was the most faithful to the contemporaneous physical reality, a compound methodology, consisting of a three-step analytical process, is here applied to the three samples. Starting from measurement of sighting angles and distances applied to a number of landmarks, a splitting of the old maps in sub-areas, probably corresponding to the set of original surveyed zones, was performed. In the area of main concern, the use of absolute measurements was avoided in order to check the level of inner congruence of the representation. Finally, a new specific error index, that can also be applied to maps lacking an explicit graphical scale, is proposed to evaluate the map truthfulness degree. The proposed method can be applied to other similar examples from ancient cartography.     

Process for the 3D virtual reconstruction of a microcultural heritage artifact obtained by synchrotron radiation CT technology using open source and free software

Computer tomography (CT) technology has greatly contributed to the feasibility and convenience of detecting and visualizing the internal material constitution and geometrical fabrication of museum artifacts. This paper presents a case study of 3D virtual reconstruction for the CT-acquisition-based study of a cultural heritage artifact. It documents the complete procedure, including the preprocessing, segmentation and visualization of the data by providing coarse interactive exploration and integrated high-quality renderings. A parallel aim achieved was to use open source tools and free software for segmentation and visualization, thus providing full transparency of the adopted methodology and 3D visualization methods, and a cost effective solution for ordinary CPU-based PC users. Furthermore, the challenges of the large data volumes involved have been addressed using preprocessing, a segmentation scheme and linked front-to-back management to keep interaction and high-quality rendering available, thus achieving corresponding demands.     

A practical approach to making accurate 3D layouts of interesting cultural heritage sites through digital models

On many occasions, the graphic information handled by people working in the cultural heritage sector is still bidimensional. Layouts showing elevations and cross sections are the most widespread tools. However, there is an increased need for carefully detailing the complexity of valuable sites with an improved accuracy. This implies the measuring and handling of three-dimensional data, using both commercial and turn-key hardware and software solutions. Taking the usual traditional process as a reference, in the present paper a new effective methodology for carrying out computer assisted delineation of layouts from cultural heritage sites, using 3D digital models, is described. The proposed procedure has been tested in five intervention projects on representative churches within the “Merindad de Aguilar de Campoo” medieval area, in the north of Spain.¹ This area has the largest collection of Romanesque art in the world, and is currently under European Heritage Site and World Heritage Site declaration process by the UNESCO.     

A web information system for the management and the dissemination of Cultural Heritage data

Safeguarding and exploiting Cultural Heritage induce the production of numerous and heterogeneous data. The management of these data is an essential task for the use and the diffusion of the information gathered on the field. Previously, the data handling was a hand-made task done thanks to efficient and experienced methods. Until the growth of computer science, other methods have been carried out for the digital preservation and treatment of Cultural Heritage information. The development of computerized data management systems to store and make use of archaeological datasets is then a significant task nowadays. Especially for sites that have been excavated and worked without computerized means, it is now necessary to put all the data produced onto computer. This allows preservation of the information digitally (in addition with the paper documents) and offers new exploitation possibilities, like the immediate connection of different kinds of data for analyses, or the digital documentation of the site for its improvement. Geographical Information Systems have proved their potentialities in this scope, but they are not always adapted to the management of features at the scale of a particular archaeological site. Therefore this paper aims to present the development of a Virtual Research Environment dedicated to the exploitation of intra-site Cultural Heritage data. The Information System produced is based on open-source software modules dedicated to the Internet, so users can avoid being software driven and can register and consult data from different computers. The system gives the opportunity to do exploratory analyses of the data, especially at spatial and temporal levels. The system is compliant to every kind of Cultural Heritage site and allows management of diverse types of data. Some experimentation has been done on sites managed by the Service of the National Sites and Monuments of Luxembourg.     

西湖申遗彰显文化魅力——本刊记者访西湖申遗专家组组长陈文锦

记者：陈老师,今天想请你谈谈杭州西湖申遗的事. 答：我作为一个了解西湖历史和文化的过来人,主要是思考者的角色,所以,下述谈话内容,也只能是我个人的观点。     

Using 3D digital models for the virtual restoration of polychrome in interesting cultural sites

In most cases, the polychrome paintings that decorated heritage buildings no longer exist or are reduced to mere remnants. These facts decontextualize the sites in their historical and artistic evolution, distort the intention under which they were conceived, and hamper their accomplishment. Current recovery methods are restricted to the stabilization of the remains in their present status, requiring a lot of completely manual work that is expensive and almost unrelated to the use of new technologies. Three-dimensional digitalization and modelling is proved to be the basis for the virtual recovery of paintings in a significant edifice. To do so, an innovative methodology is presented that allows the 3D geometric information of a site (captured using a laser scanner) to be combined with specially designed 2D artistic images. The resulting 3D digital models can then be focused, with high efficiency projectors, on the equivalent area of the original site, and also used as raw material to compose a video-projection without perspective effects to emulate, with due rigour, the primitive appearance, its evolution along time, the effects of the deterioration, or other interesting aspects. The results obtained at Sta. María de Mave (Palencia, Spain) are presented, supporting the potential of this new methodology not only as a scientific way to discuss possible restoration hypotheses with experts or as a didactic tool for narrating the historical evolution of a monument, but also as a spectacular show for tourists.     

Smart surfaces for architectural heritage: Preliminary results about the application of TiO2-based coatings on travertine

The development and application of self-cleaning treatments on historical and architectural stone surfaces could be a significant improvement in conservation, protection and maintenance of Cultural Heritage. In this paper, a TiO₂-based coating has been investigated in order to evaluate its possible use as a self-cleaning treatment. This coating was obtained by a sol-gel and a hydrothermal (134 °C) processes and then it was applied on travertine (a limestone often used in historical and monumental buildings) in two ways, obtaining a single-layer and a three-layer treatment, respectively. In order to verify its potential use in the field of Cultural Heritage, the maintenance of appearance properties of the treated travertine surfaces was monitored by colour and gloss analyses. Besides, de-pollution and soiling removal tests were carried out under ultraviolet-light exposure to evaluate photo-induced effects and self-cleaning efficiency. Results seem to allow the use of TiO₂-based treatments on historical and architectural surfaces made up by travertine, where de-pollution and self-cleaning photo-induced effects are well evident, maintaining their original visual appearance. Anyway, before applying TiO₂-based coatings as conservative treatments, further tests are needed especially on their durability, that is mandatory for Cultural Heritage applications. On-site test in an urban environment and accelerated test by weatherometer are currently under way.     

Surface analysis of stone materials integrating spatial data and computer vision techniques

This paper deals with a possible application of computer vision techniques in the field of Cultural Heritage. These techniques allow an effective integration of data from different sources. Particular consideration will be given to an accurate geometric analysis of the zone under study in order to detect degradation damage in historical building-stone materials. To this end, we employ a computer vision technique, known as the Shape from Shading method, for which a photographic image of the stone material under consideration is the only input data required. By using this method, it is possible to recover, under some constraints, the shape of the three-dimensional surface of the object from the photographic image. In order to improve the results, in this paper, we implement this technique by using an optimization approach which allows a suitable integration of photographic and spatial data, the latter of which is obtained by a topographical device. We outline the potentialities of the method which mainly consist of two relevant capabilities. The first one is the geometric shape reconstruction of the surface material at a resolution much higher than the one allowed by topographical acquisition. The second one is the correction of the lighting-induced distortions in the photographic image. Such a correction is relevant for further image-based analysis of the degradation of the stone material. Experimental results, obtained by using both photographic and spatial data relative to a pudding stone with degradation, are presented and discussed.     

The contribution of urban-scale environmental monitoring to materials diagnostics: A study on the Cathedral of Modena (Italy)

The problem of environmental monitoring aimed at identifying and evaluating the weathering mechanisms affecting historical stoneworks is here discussed and a methodology based on the use of already available, long record, urban-scale environmental data is proposed. An example of its application to the Cathedral of Modena (Italy, XII-XIV century, included in the UNESCO's World Heritage List) is then presented. In this case, the methodology allowed the identification of the main degradation causes, which found significant confirmation by material diagnostics on the available samples and finite element structural modelling. Thanks to the decay causes identification allowed by the proposed methodology, more effective restoration procedures can be outlined.     

Cultural heritage interactive 3D models on the web: An approach using open source and free software

Cultural heritage sites and artefacts get a significant added value from high-resolution 3D models. These models are increasingly available due to improvements in technology and to higher integration of survey techniques such as laser scanning and photogrammetry. In this paper we present a case study on the development of a web-based application for user access and interactive exploration of three-dimensional models by providing integrated geometrical and non-geometrical information into an intuitive interface. The main feature of this interactive system is to provide the user with a completely new visit experience based on a free interactive exploration interface of the object (i.e., not constrained by any predefined pathway) and on the opportunity to get more detailed information on specific parts of interest. A parallel aim achieved was to use, in data processing and in the architecture, open source tools and free software, thus providing full transparency on adopted methodology and data processing methods, and a cost effective solution both for server and client. Furthermore, the aspect of data size has been considered using a segmentation and simplification scheme and server-side data management to keep transmission size to a minimum, thus improving access speed.     

Documentation of cultural heritage using digital photogrammetry and laser scanning

Precise documentation of cultural heritage status is essential for its protection and scientific studies carried out during the restoration and renovation process. The close range photogrammetry has been used successfully for documentation of cultural heritage. With recent developments in computer and information technologies, this well-known traditional method has been replaced with digital close-range photogrammetry. This new method offers us new opportunities such as automatic orientation and measurement procedures, generation of 3D vector data, digital ortho-image and digital surface model. Terrestrial laser scanning is another technology that in recent years has become increasingly popular for documentation which provides very dense 3D points on an object surface with high accuracy. In addition, the 3D model and digital ortho-image can be easily generated using generated 3D point cloud and recorded digital images.     

Methods for 3D digitization of Cultural Heritage

Complete digital recording of Cultural Heritage is a multidimensional process. It depends highly on the nature of the subject of recording as well as the purpose of its recording. The whole process involves the three-dimensional digitization, digital data processing and storage, archival and management, representation and reproduction. In this paper we briefly review methods for three-dimensional digitization that are applicable to cultural heritage recording.     

Digital preservation of Brazilian indigenous artworks: Generating high quality textures for 3D models

Three-dimensional (3D) digital preservation aims at generating 3D models of objects that have cultural or scientific value. It allows realistic visualization of objects through virtual museums or scientific applications, and the restoration of the preserved object in case of natural wear or accidents. This work contributes to this research area by presenting a method to improve color texture quality of 3D models obtained from color and depth images of a laser scanner. Although this device offers precise depth information, the resulting color information is still poor and limits the generation of realistic textures. Our approach is to capture photographs of the object with a high-resolution digital camera and use them to generate a new color texture for the 3D model. Our work proposes a practical technique, easy to replicate, to generate high quality textures for 3D models from photographs. The method is composed by three main steps: (1) calibration of the image acquisition devices; (2) data acquisition; and (3) texture generation. In this paper, we detail our color texture generation method and apply it on the digital preservation of many artworks made by native Brazilians (indians) from the Wauja and Karaja communities. These indigenous communities are acknowledged as great ceramic artists, each bearing their own main themes, using a very rich symbolism in their paintings. Their artworks represent important aspects of the native South American culture and their digital preservation is motivated by three main reasons: (1) their fragility; (2) the paintings loose their original appearance with time; and (3) the possibility of extinction of these communities. We present several results of preserved artworks with enhanced quality realistic texture maps. Also, we present a methodology to analyze the quality and accuracy of texture maps. The resulting 3D models can be visualized through a tool we developed to support the virtual exhibit of 3D preserved heritage.     

3D preserving xviii century barroque masterpiece: Challenges and results on the digital preservation of Aleijadinho's sculpture of the Prophet Joel

We present our recent efforts in the digital preservation of a set of baroque sculptures made by Antônio Francisco Lisboa, known as O. Aleijadinho, which is an important American baroque artist. The set was made in the beginning of the xix century and is composed of 12 near real sized sculptures, hand-carved in soapstone. These sculptures represent 12 of the 16 prophets from the Holy Bible and are part of a UNESCO World Heritage Site. Our group has been collaborating with UNESCO in a project that aims to preserve all these statues. We hereby present our initial efforts, consisting of the 3D digital preservation of the Prophet Joel sculpture. We developed a complete 3D digital preservation pipeline composed of four main stages: data acquisition, 3D reconstruction, texture generation and 3D model visualization. By evaluating our results in this first sculpture, we discuss the improvements we conceived before applying our pipeline in the remaining ones. Finally, we present the 3D model of the Prophet which registers the sculpture's current state and will be used in restoration, research and educational activities. We believe this contribution may be useful to guide further research on similar scenarios, showing how to avoid some practical mistakes and achieve good results.