Papers by Georgia Kontogianni
Digital , 2022
In recent years, the rapid development of technology has offered scientists new powerful tools. E... more In recent years, the rapid development of technology has offered scientists new powerful tools. Especially in the field of cultural heritage documentation, modern digital media are an integral part, contributing significantly to the process of recording, managing, and displaying architectural monuments, archaeological sites, and art objects in a fast and accurate way. Digital technologies have made it possible to produce accurate digital copies of heritage sites and contribute to their salvation
and conservation. At the top of the hill of Agios Fokas, acropolis of the ancient Demos of Kymissaleis, are the remains of a small Hellenistic temple of the 3rd–2nd century BC. This article proposes a virtual reconstruction of the temple on the acropolis of Kymissala. The geometric documentation of the temple and the creation of a three-dimensional model with its virtual reconstruction are analyzed. Modern photogrammetric methods are applied by taking digital images in the context of the experimental application of a relatively simple and semi-automatic method that does not require highly specialized knowledge and therefore can be used by non-specialists. With the use of modeling software, a three-dimensional model of the temple is created with the main goal of its virtual reconstruction.
Virtual Archaeology Review, 2020
Archaeological restoration of monuments is a practice requiring extreme caution and thorough stud... more Archaeological restoration of monuments is a practice requiring extreme caution and thorough study. Archaeologists and conservation experts are very reluctant to proceed to restoration and indeed to reconstruction actions without detailed consultation and thought. Nowadays, anastylosis executed on the real object is practically prohibited. Contemporary technologies have provided archaeologists and other conservation experts with the tools to embark on virtual restorations or anastyloses, thus testing various alternatives without physical intervention on the monument itself. In this way, the values of the monuments are respected according to international conventions. In this paper, two such examples of virtual archaeological anastyloses of two important Macedonian tombs in northern Greece are presented. The anastyloses were performed on three-dimensional (3D) models which have been produced using modern digital 3D documentation techniques, such as image-based modelling and terrestri...
ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, 2015
3D reconstruction relies on accurate detection, extraction, description and matching of image fea... more 3D reconstruction relies on accurate detection, extraction, description and matching of image features. This is even truer for complex architectural scenes that pose needs for 3D models of high quality, without any loss of detail in geometry or color. Illumination conditions influence the radiometric quality of images, as standard sensors cannot depict properly a wide range of intensities in the same scene. Indeed, overexposed or underexposed pixels cause irreplaceable information loss and degrade digital representation. Images taken under extreme lighting environments may be thus prohibitive for feature detection/extraction and consequently for matching and 3D reconstruction. High Dynamic Range (HDR) images could be helpful for these operators because they broaden the limits of illumination range that Standard or Low Dynamic Range (SDR/LDR) images can capture and increase in this way the amount of details contained in the image. Experimental results of this study prove this assumpt...
ISPRS Archives-Volume XLII-2/W17, 2019
In archaeological excavations, many small fragments or artefacts are revealed whose fine details ... more In archaeological excavations, many small fragments or artefacts are revealed whose fine details sometimes should be captured in 3D. In general, 3D documentation methods fall into two main categories: Range-Based modelling and Image-Based modelling. In Range Based modelling, a laser scanner (Time of Flight, Structured light, etc.) is used for the raw data acquisition in order to create the 3D model of an object. The above method is accurate enough but is still very expensive in terms of equipment. On the other hand, Image-Based modelling, is affordable because the equipment required is merely a camera with the appropriate lens, and possibly a turntable and a tripod. In this case, the 3D model of an object is created by suitable processing of images which are taken around the object with a large overlap. In this paper, emphasis is given on the effectiveness of 3D models of frail archaeological finds originate from the palatial site of Ayios Vasileios in Laconia in the southeastern Peloponnese, using low-cost equipment and methods. The 3D model is also produced using various, mainly freeware, hence low-cost, software and the results are compared to those from a well-established commercial one.
ISPRS Archives-Volume XLII-2/W11, 2019
Archaeology as a science is based on finding and displaying the remains of the past. In recent ye... more Archaeology as a science is based on finding and displaying the remains of the past. In recent years, with the progress of technology, the science of archeology has been expanding and evolving. Three-dimensional digitization has become an integral part of the archiving, documentation and restoration effort of cultural heritage, offering important benefits in studies for reconstruction and restoration tasks of architectural creations, archaeological sites, historic monuments and objects of art in general. The three-dimensional models are now available for many applications. In this paper such 3D models of two prominent Macedonian tombs in Northern Greece were exploited for their virtual restoration. Virtual restoration of monuments is of special importance to archaeological research, as it provides the necessary tools to investigate alternative solutions to the serious issue of archaeological restoration. These solutions do not interfere with the real monument, thus respecting its value and the international conventions. Digital 3D models have begun to be more beneficial in a science such as archaeology as they offer easy access to both archaeological and geometric information to a wider audience as well as a high degree of interaction possibilities with the user.
ISPRS Archives-Volume XLII-2/W15, 2019
Small artefacts pose many challenges to 3D documentation techniques due to their often complex de... more Small artefacts pose many challenges to 3D documentation techniques due to their often complex details, which are very difficult to capture completely in 3D. Small objects may also have characteristics that are not optimal for 3D documentation, e.g. glossiness, shininess, textureless surfaces, etc. Furthermore, hidden parts of the artefact cause occlusions and obstructions, which may complicate the data acquisition process, since additional images or scan data are necessary in order to compensate for these restrictions. All these aspects increase acquisition and data processing times. Currently, the two main categories of 3D documentation methods are Image Based Modelling (IBM) and Range Based Modelling (RBM). In this paper, preliminary investigations aimed at evaluating the accuracy and performance of a front surface mirror in Image Based Modelling for small artefacts are presented. These results are then compared to a reference model generated from the artefact using a structured light system.
3D reconstruction of small artefacts is very significant in order to capture the details of the w... more 3D reconstruction of small artefacts is very significant in order to capture the details of the whole object irrespective of the documentation method which is used (Ranged Based or Image Based). Sometimes it is very difficult to achieve it because of hidden parts, occlusions, and obstructions which the object has. Hence, more data are necessary in order to 3D digitise the whole of the artefact leading to increased time for collecting and consequently processing the data. A methodology is necessary in order to reduce the collection of the data and therefore their processing time especially in cases of mass digitisation. So in this paper, the use of mirrors in particular high-quality mirrors in the data acquisition phase for the 3D reconstruction of small artefacts is investigated. Two case studies of 3D reconstruction are presented: the first one concerns Range-Based modelling especially a Time of Flight laser scanner is utilised and in the second one Image-Based modelling technique is implemented.
Serious Games applications are implemented in many scientific fields including cultural heritage.... more Serious Games applications are implemented in many scientific fields including cultural heritage. Virtual museums mainly utilise game technologies for the provision of a means for digital representation of the cultural heritage sites. Many such applications and projects were developed in recent years. In this paper, the development of an application of a virtual museum for the Stoa of Attalos in Athens is presented. The application allows the user to split the visit in two sections. The first one concerns the exhibits of the Stoa of Attalos and the second one focuses on a specialized part of the museum, a shop of the Stoa which conveys the information about the wine production and trade routes in the Eastern Mediterranean basin. The 3D models used in the application were created with automated image based reconstruction method in order to present them as realistically as possible to the virtual visitor.
International Journal of Computational Methods in Heritage Science, 2017
In the cultural heritage field, many Serious Games applications have been developed whose goal is... more In the cultural heritage field, many Serious Games applications have been developed whose goal is to educate players and users not particularly specialized or familiar with this field. On the other hand, 3D models of cultural heritage objects created with precise 3D modelling methods can be a very useful asset for these applications. In this paper a composite Serious Game for the Stoa of Attalos, a prominent monument in the Ancient Athens Agora, is developed and presented. 3D models are used, which were produced mainly with automated image based modelling techniques. The creation of the 3D models is described and presented along with the development of the application, which offers three options for the player. These options are: a quiz game, a 3D visual quiz and a virtual museum. The user interaction is described and, based on an evaluation questionnaire, the application is assessed by a group of people in the Cultural Heritage field.
The 3D digitisation of small artefacts is a very complicated procedure because of their complex m... more The 3D digitisation of small artefacts is a very complicated procedure because of their complex morphological feature structures, concavities, rich decorations, high frequency of colour changes in texture, increased accuracy requirements etc. Image-based methods present a low cost, fast and effective alternative because laser scanning does not meet the accuracy requirements in general. A shallow Depth of Field (DoF) affects the image-based 3D reconstruction and especially the point matching procedure. This is visible not only in the total number of corresponding points but also in the resolution of the produced 3D model. The extension of the DoF is a very important task that should be incorporated in the data collection to attain a better quality of the image set and a better 3D model. An extension of the DoF can be achieved with many methods and especially with the use of the focus stacking technique. In this paper, the focus stacking technique was tested in a real-world experiment to digitise a museum artefact in 3D. The experiment conditions include the use of a full frame camera equipped with a normal lens (50mm), with the camera being placed close to the object. The artefact has already been digitised with a structured light system and that model served as the reference model in which 3D models were compared and the results were presented.
Digital technologies for representing cultural heritage assets of any size are already maturing. ... more Digital technologies for representing cultural heritage assets of any size are already maturing. Technological progress has greatly enhanced the art of virtual representation and, as a consequence, it is all the more appealing to the general public and especially to younger generations. The game industry has played a significant role towards this end and has led to the development of edutainment applications. The digital workflow implemented for developing such an application is presented in this paper. A virtual museum has been designed and developed, with the intention to convey the history of trade in the Eastern Mediterranean area, focusing on the Aegean Sea and five productive cities-ports, during a period of more than 500 years. Image based modeling methodology was preferred to ensure accuracy and reliability. The setup in the museum environment, the difficulties encountered and the solutions adopted are discussed, while processing of the images and the production and finishing of the 3D models are described in detail. The virtual museum and edutainment application, MEDWINET, has been designed and developed with the intention to convey the essential information of the wine production and trade routes in the Eastern Mediterranean basin. The user is able to examine the 3D models of the amphorae, while learning about their production and use for trade during the centuries. The application has been evaluated and the results are also discussed.
The Depth of Field (DoF) is a vital factor in photogrammetric applications. Its effect is in most... more The Depth of Field (DoF) is a vital factor in photogrammetric applications. Its effect is in most cases pretty obvious especially when capturing small artefacts. It is very important to observe its behaviour as it affects the ability to capture all the details of an object. Focus stacking is a technique in computational photography, in which a set of images focused on different planes with limited DoF are combined in order to considerably extend the DoF. Today, there is a number of focus stacking methods that can be applied in order to produce a full-focus image. In this paper, we investigate the application and effects of focus stacking on SfM-MVS 3D reconstruction. Specifically, our experiment involves the 3D reconstruction of a selected artefact using both traditional all-focus photography and focus stacking. The artefact has already been digitised with a high accuracy and resolution structured light 3D scanner, and that 3D model served as the reference model, with which SfM models were compared. We discuss on these fist results and present some preliminary assessment on the application of focus stacking for the SfM-MVS-based 3D reconstruction.
In the field of Cultural Heritage there are many Serious Games applications. 3D models of cultura... more In the field of Cultural Heritage there are many Serious Games applications. 3D models of cultural heritage objects created with 3D modelling methods preserving realism and detail can be a very useful tool for Serious Games if exploited correctly and suitably. In this paper a composite SG application is developed and presented using such realistic 3D models produced by Geomatics techniques. The construction of these 3D models is presented along with the application, which consists of three different options for the user: A virtual navigation to the site with some questions, a visit to the museum of a monument and an educational quiz game concerning the architectural reconstruction of this monument.
Recent advances in contemporary technologies have greatly affected everyday life. In the field of... more Recent advances in contemporary technologies have greatly affected everyday life. In the field of cultural heritage, ICT (Information Communication Technologies) have enabled applications for the thorough multi-dimensional geometric documentation and consequently for the realistic visualization of monuments and artifacts. At the same time the driving force of technology is the game industry. Games and especially Serious Games can be put at the service of cultural heritage, education and tourism exploiting the aforementioned advances and especially the textured three dimensional models. They constitute an attractive platform enabling people to get acquainted with the heritage treasures and get motivated to visit the place and admire the treasures live. In this paper this technological merger is explained and three interconnected applications are presented in order to prove the concept through these implementations. They concern the development of Serious Games for an archaeological site, which aim at the trivial or more specialized information dissemination about that site, while familiarizing the prospect visitor with the environment and the monuments of the site offering the possibility of virtually visiting them. Moreover the development of a virtual museum within a game development environment is presented, which provides the possibility to learn about each exhibit, but also it offers the opportunity to the user to closely examine the exhibits through rotating their three dimensional models. All these examples use realistic models produced for documentation purposes, which convey the real impression of the monuments visualized to the user
Digital technologies have affected significantly many fields of computer graphics such as Serious... more Digital technologies have affected significantly many fields of computer graphics such as Serious Games. These games are used for educational proposes in many scientific areas one of which is Digital Cultural Heritage. 3D textured models may be a useful tool for developing Serious Games in this field. In this paper a first attempt of creating a Serious Game for the Ancient Agora of Athens is presented. The scope of this game is to help people who are not experts such as school pupils, college students, tourists, museum visitors etc. to gain simple knowledge about the Agora and its monuments. Unity 3D software was used for the game development in which different kinds of realistic photogrammetric data were used. The scenario of the game includes virtual tours of the area in different eras and a simple quiz game. In this quiz game there are questions with three possible answers of which the user is expected to select the right one. In case of a correct answer the game continues to the next question. If the answer is wrong the user is presented with the correct answer and an explanation for his error. The game scenario will include more options in order to make the game more attractive for the player.
Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XL-5/W7, 249-255, Sep 2015
Digital technologies have affected significantly many fields of computer graphics such as Games ... more Digital technologies have affected significantly many fields of computer graphics such as Games and especially the field of the Serious Games. These games are usually used for educational proposes in many fields such as Health Care, Military applications, Education, Government etc. Especially Digital Cultural Heritage is a scientific area that Serious Games are applied and lately many applications appear in the related literature. Realistic 3D textured models which have been produced using different photogrammetric methods could be a useful tool for the creation of Serious Game applications in order to make the final result more realistic and close to the reality. The basic goal of this paper is how 3D textured models which are produced by photogrammetric methods can be useful for developing a more realistic environment of a Serious Game. The application of this project aims at the creation of an educational game for the Ancient Agora of Athens. The 3D models used vary not only as far as their production methods (i.e. Time of Flight laser scanner, Structure from Motion, Virtual historical reconstruction etc.) is concerned, but also as far as their era as some of them illustrated according to their existing situation and some others according to how these monuments looked like in the past. The Unity 3D® game developing environment was used for creating this application, in which all these models were inserted in the same file format. For the application two diachronic virtual tours of the Athenian Agora were produced. The first one illustrates the Agora as it is today and the second one at the 2nd century A.D. Finally the future perspective for the evolution of this game is presented which includes the addition of some questions that the user will be able to answer. Finally an evaluation is scheduled to be performed at the end of the project.
3D reconstruction relies on accurate detection, extraction, description and matching of image fea... more 3D reconstruction relies on accurate detection, extraction, description and matching of image features. This is even truer for complex architectural scenes that pose needs for 3D models of high quality, without any loss of detail in geometry or color. Illumination conditions influence the radiometric quality of images, as standard sensors cannot depict properly a wide range of intensities in the same scene. Indeed, overexposed or underexposed pixels cause irreplaceable information loss and degrade digital representation. Images taken under extreme lighting environments may be thus prohibitive for feature detection/extraction and consequently for matching and 3D reconstruction. High Dynamic Range (HDR) images could be helpful for these operators because they broaden the limits of illumination range that Standard or Low Dynamic Range (SDR/LDR) images can capture and increase in this way the amount of details contained in the image. Experimental results of this study prove this assumption as they examine state of the art feature detectors applied both on standard dynamic range and HDR images.
During recent years Terrestrial Laser Scanning tends to be challenged by fast algorithms, which d... more During recent years Terrestrial Laser Scanning tends to be challenged by fast algorithms, which detect millions of conjugate points on overlapping digital images. Their relative or absolute position can also be determined and this procedure results in dense point clouds, very often with colour information. These Structure-from-Motion (SfM) algorithms are being constantly tested and evaluated with a high percentage of success. On the other hand digital imaging has enabled the confrontation of adverse lighting conditions, especially using High Dynamic Range (HDR) imaging. In this paper HDR digital images are being tested with SfM algorithms. It is assumed that images with better lighting conditions could possibly enhance the results of the SfM algorithms as these images offer better depiction of the object. The first results of these tests are presented and evaluated.
Augmented reality is a rapidly evolving technology that enriches reality with computer generated ... more Augmented reality is a rapidly evolving technology that enriches reality with computer generated information as well as a powerful tool that provides innovative ways of information access at cultural heritage sites. In this paper, an augmented reality application that allows the visualization of a part of the Middle Stoa in the Ancient Agora of Athens is presented. Users of this application, pointing their tablet PC at the present situation, have the opportunity to see what this building looked like in ancient times, as its three dimensional model is displayed on the camera view of their device, projected on the modern-
day ruins.
ΛΕΞΕΙΣ ΚΛΕΙΔΙΑ: Εικονική ανακατασκευή, Αληθοφάνεια των δεδομένων, Εικονικό μοντέλο, Μεσαία Στοά
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Papers by Georgia Kontogianni
and conservation. At the top of the hill of Agios Fokas, acropolis of the ancient Demos of Kymissaleis, are the remains of a small Hellenistic temple of the 3rd–2nd century BC. This article proposes a virtual reconstruction of the temple on the acropolis of Kymissala. The geometric documentation of the temple and the creation of a three-dimensional model with its virtual reconstruction are analyzed. Modern photogrammetric methods are applied by taking digital images in the context of the experimental application of a relatively simple and semi-automatic method that does not require highly specialized knowledge and therefore can be used by non-specialists. With the use of modeling software, a three-dimensional model of the temple is created with the main goal of its virtual reconstruction.
day ruins.
and conservation. At the top of the hill of Agios Fokas, acropolis of the ancient Demos of Kymissaleis, are the remains of a small Hellenistic temple of the 3rd–2nd century BC. This article proposes a virtual reconstruction of the temple on the acropolis of Kymissala. The geometric documentation of the temple and the creation of a three-dimensional model with its virtual reconstruction are analyzed. Modern photogrammetric methods are applied by taking digital images in the context of the experimental application of a relatively simple and semi-automatic method that does not require highly specialized knowledge and therefore can be used by non-specialists. With the use of modeling software, a three-dimensional model of the temple is created with the main goal of its virtual reconstruction.
day ruins.
and especially the Serious Games field. This kind of games is usually used for
educational proposes in many scientific fields such as Health Care, Military,
Education etc. Digital Cultural Heritage is a scientific field in which Serious Games are
gradually applied and many applications have been developed according to the
literature.
Realistic 3D models which have been produced using different photogrammetric
methods could be a useful tool for the creation of Serious Games applications in
order to make the final result more realistic and closer to the reality.
The basic goal of this thesis is the development of a Serious Game for the Ancient
Agora of Athens by using different kind of 3D documentation data created in
previous projects. These models vary not only as far as their production methods
(Time of Flight Laser scanner, Structure from Motion, Virtual Historical
reconstruction etc.) is concerned, but also as far as their era, because some of them
are illustrated according the existing situation and some others according to how
these monuments would have looked like in the past.
The Unity 3D Game development engine was used for the game development in
which all these models were inserted in the same file format. The scenario of the
game includes two virtual tours of the area in different eras and a quiz game. In this
quiz game question are posed to the user for each monument with three possible
answers of which the player should select the correct one. In case that the answer is
right he will continue with the next question. In case that the answer is wrong the
player will be presented with the correct answer and an explanation about his
mistake. Furthermore a preliminary stage about ancient Greek temples and their
orders is created in order to help the players to acquire more knowledge and facts
about Ancient Greek architecture.
The evaluation of the game was carried out by a group of people, experienced and
non-experienced in Cultural Heritage field, who played and evaluated the game by
filling in a carefully prepared online questionnaire. The game was improved
according these evaluations for a better result. Finally some concluding remarks and
the future evolution of this game is presented.