Papers by Anthousis Andreadis
3D scanning in cultural heritage (CH) is used in most cases either for the faithful generation of... more 3D scanning in cultural heritage (CH) is used in most cases either for the faithful generation of digital models of CH objects or for visualization purposes. In this paper, we move a step further and concentrate on documenting the requirements and our experience in 3D scanning for alternative CH application scenarios, where digitization is not the end product, but rather the means to augment the existing information and acquired data. In our work, which is part of the PRESIOUS EU-funded project, we aim at utilizing and inventing new methodologies and technologies for the prediction of geometric information on CH data, ranging from the digitization process itself to geometric reassembly, shape prediction and simulation/prediction of monument degradation. To this end, the scanning requirements of the different processing tasks are given, including specialized high-definition scans for erosion measurement, meso-scale digitization for reassembly as well as for the visualization of the results. Important practical lessons are drawn and the actual digitisation pipelines of state-of-art 3D digitisation technologies are given. A practical discussion summarizes our multi-scale digitisation experience (giving the accuracy, required time and resulting data size that we observed), mainly drawn from the digitization activities at the Nidaros Cathedral,
2015 Digital Heritage, 2015
We present a novel and generic user-guided approach for the digital reconstruction of cultural he... more We present a novel and generic user-guided approach for the digital reconstruction of cultural heritage finds from fragments, which operates directly on generic 3D objects. Central to our approach is a three-tier geometric registration approach that addresses the reassembly problem using i) the contact surface of the fractured objects, ii) feature curves on the intact surfaces and iii) partial object symmetries. In contrast to most existing methodologies, our approach is more generic and addresses even the most difficult cases, where contact surface is unusable, small or absent. We evaluate our method using digitized fragments from the Nidaros Cathedral.
Ray Tracing is a rendering method for the presentation of three dimensional images on two dimensi... more Ray Tracing is a rendering method for the presentation of three dimensional images on two dimensional displays. One of the greatest challenges of ray tracing is efficient execution, since many times the method is dismissed as being too computationally expensive. In the current work we present the application of a novel method to accelerate the most intensive part of the computation of secondary-rays (reflection, refraction and shadow rays) the ray-primitive intersection tests. The main idea behind this acceleration technique is the use of four-dimensional fields (displacement fields) for each object that describe the distance from an augmented bounding sphere to the actual object surface, in every direction, for all positional samples on the sphere. Ray tracing is accelerated by replacing the often numerous distance-sorted ray-polygon hit queries, by a simple and of constant time displacement field indexing mechanism. Furthermore the GPU implementation of the method allows the explo...
Abstract: In this paper we present a novel generic method for the fast and accurate computation o... more Abstract: In this paper we present a novel generic method for the fast and accurate computation of geometric features at multiple scales. The presented method works on arbitrarily complex models and operates in the parametric space. The majority of the existing methods compute local features directly on the geometric representation of the model. Our approach decouples the computational complexity from the underlying geometry and in contrast to other parametric space methods, it is not restricted to a specific feature or parameterization of the surface. We show that the method performs accurately and at interactive rates, even for large feature areas of support, rendering the method suitable for animated shapes. 1
Journal on Computing and Cultural Heritage
The problem of the restoration of broken artifacts, where large parts could be missing, is of hig... more The problem of the restoration of broken artifacts, where large parts could be missing, is of high importance in archaeology. The typical manual restoration can become a tedious and error-prone process, which also does not scale well. In recent years, many methods have been proposed for assisting the process, most of which target specialized object types or operate under very strict constraints. We propose a digital shape restoration pipeline consisting of proven, robust methods for automatic fragment reassembly and shape completion of generic three-dimensional objects of arbitrary type. In this pipeline, first we introduce a novel unified approach for handling the reassembly of objects from heavily damaged fragments by exploiting both fracture surfaces and salient features on the intact sides of fragments, when available. Second, we propose an object completion procedure based on generalized symmetries and a complementary part extraction process that is suitable for driving the fab...
Communications in Computer and Information Science, 2016
The reassembly of fractured 3D objects from their parts is an important problem in cultural herit... more The reassembly of fractured 3D objects from their parts is an important problem in cultural heritage and other domains.We approach reassembly from a geometric matching perspective and propose a pipeline for the automatic solution of the problem, where an efficient and generic three-level coarse-to-fine search strategy is used for the underlying global optimization. Key to the efficiency of our approach is the use of a discretized approximation of the surfaces' distance field, which significantly reduces the cost of distance queries and allows our method to systematically search the global parameter space with minimal cost. The resulting reassembly pipeline provides highly reliable alignment, as demonstrated through the reassembly of fractured objects from their fragments and the reconstruction of 3D objects from partial scans, showcasing the wide applicability of our methodology.
2011 Third International Conference on Games and Virtual Worlds for Serious Applications, 2011
Virtual environments have been valued as being extremely motivating for learners and therefore ar... more Virtual environments have been valued as being extremely motivating for learners and therefore are employed as an innovative, more accessible framework to deliver education and entertainment to the public. Recent advances in creating videogame applications imbedded with effective learning principles, along with the evolution of human computer interfaces performed within the entertainment industry, suggests that a combination of successful practices in these areas could potentially transform virtual environments to a significant educational tool that could facilitate the learning process. This paper describes a virtual reality exhibit implemented for the museum of Thermopylae located at the site of the original battle, near the city of Lamia in Greece. We utilized storytelling techniques and principles of modern videogames to disseminate historical knowledge about the battle and the associated legends. After describing the hardware and software components comprising this installation we elaborate over the educational techniques designed to reinforce the strength of virtual reality technology as a mean of designing educational experiences in the context of historical events.
2010 14th Panhellenic Conference on Informatics, 2010
The employment of innovative forms of technology in the areas of art and entertainment is receivi... more The employment of innovative forms of technology in the areas of art and entertainment is receiving significant attention from the research community in the context of evaluating new forms of expression. Recent developments in tangible interaction, pervasive sensing, wearable computing, and mobile communications bring about the potential to connect, in an unprecedented manner, persons to places (real and virtual) and media, as well as to other persons and objects. The work presented here brings together a research team that is multidisciplinary, scientists, engineers, 3D-artists along with members from the art domain such as stage director, theatrical costumier, choreographer and actors, in order to synthesize a live theatrical performance that jointed technology and art. Real time motion capture data was streamed on a multi-screen topology, while real time generated virtual scenery was creating the virtual context of each act. Live actors were interacting with a digital avatar that was rigged to a motion capture suit through out the theatrical act. The entire setup was evaluated on a theatrical case study that was presented to audience at the "Theatron", a reconfigurable space at the cultural center of Hellenic Cosmos, providing significant feedback on the acceptance of utilizing such a technology both from the audience perspective as well as the experts that live theatrical performances involve.
Lecture Notes in Computer Science, 2013
Proceedings of the 2013 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining - ASONAM '13, 2013
ABSTRACT The paper shows how different concepts and technologies, such as high quality multimedia... more ABSTRACT The paper shows how different concepts and technologies, such as high quality multimedia content production and delivery, social media interaction, and methodologies for monitoring and analysing social network activity, can be practically combined with traditional virtual reality installations into an innovative experimental system that enhances the experience of the visitors in cultural educational centers. Apart from offering a modern, immersive, richer experience to the visitors, the proposed system involves significant benefits for the organizers as well, supplying them with valuable feedback extracted from the monitoring and analysis mechanisms. The experimental system has been successfully deployed and used in the Foundation of the Hellenic World cultural center.
2013 8th International Workshop on Semantic and Social Media Adaptation and Personalization, 2013
ABSTRACT The advancement of ICT has brought about significant changes in the way the cultural and... more ABSTRACT The advancement of ICT has brought about significant changes in the way the cultural and creative industries work as well as in the experience they offer. However there is still a lot of potential that can be leveraged to advance the state of the art in the way the public shares collective cultural experiences. In this paper, we employ different concepts and technologies, such as high quality multimedia content production and delivery, social media interaction, and methodologies for monitoring and analyzing social network activity, to revamp the experience offered in cultural and educational centres. In addition to an increased Quality of Experience, the proposed system involves significant benefits for the organizers as well, providing them with feedback based on social analytics. The experimental system has been successfully deployed and used in the "Hellenic Cosmos" cultural center.
The reassembly of fractured 3D objects from their parts is an important problem in cultural herit... more The reassembly of fractured 3D objects from their parts is an important problem in cultural heritage and other domains. We approach reassembly from a geometric matching perspective and propose a pipeline for the automatic solution of the problem, where an efficient and generic three-level coarse-to-fine search strategy is used for the underlying global optimization. Key to the efficiency of our approach is the use of a discretized approximation of the surfaces’ distance field, which significantly reduces the cost of distance queries and allows our method to systematically search the global parameter space with minimal cost. The resulting reassembly pipeline provides highly reliable alignment, as demonstrated through the reassembly of fractured objects from their fragments and the reconstruction of 3D objects from partial scans, showcasing the wide applicability of our methodology.
We present a new method for the completion of partial globally-symmetric 3D objects, based on the... more We present a new method for the completion of partial globally-symmetric 3D objects, based on the detection of partial and approximate symmetries in the incomplete input dataset. In our approach, symmetry detection is formulated as a constrained sparsity maximization problem, which is solved efficiently using a robust RANSAC-based optimizer. The detected partial symmetries are then reused iteratively, in order to complete the missing parts of the object. A global error relaxation method minimizes the accumulated alignment errors and a non-rigid registration approach applies local deformations in order to properly handle approximate symmetry. Unlike previous approaches, our method does not rely on the computation of features, it uniformly handles translational, rotational and reflectional symmetries and can provide plausible object completion results, even on challenging cases, where more than half of the target object is missing. We demonstrate our algorithm in the completion of 3D scans with varying levels of partiality and we show the applicability of our approach in the repair and completion of heavily eroded or incomplete cultural heritage objects.
We present a novel and generic user-guided approach for the digital reconstruction of cultural he... more We present a novel and generic user-guided approach for the digital reconstruction of cultural heritage finds from fragments, which operates directly on generic 3D objects. Central to our approach is a three-tier geometric registration approach that addresses the reassembly problem using i) the contact surface of the fractured objects, ii) feature curves on the intact surfaces and iii) partial object symmetries. In contrast to most existing methodologies, our approach is more generic and addresses even the most difficult cases, where contact surface is unusable, small or absent.We evaluate our method using digitized fragments from the Nidaros Cathedral.
The problem of object restoration from eroded fragments where large parts could be missing is of ... more The problem of object restoration from eroded fragments where large parts could be missing is of high relevance in archaeology. Manual restoration is possible and common in practice but it is a tedious and error-prone process, which does not scale well. Solutions for specific parts of the problem have been proposed but a complete reassembly and repair pipeline is absent from the bibliography. We propose a shape restoration pipeline consisting of appropriate methods for automatic fragment reassembly and shape completion. We demonstrate the effectiveness of our approach using real-world fractured objects.
The registration of two geometric surfaces is typically addressed using variants of the Iterative... more The registration of two geometric surfaces is typically addressed using variants of the Iterative Closest Point (ICP) algorithm. The Sparse ICP method formulates the problem using sparsity-inducing norms, significantly improving the resilience of the registration process to large amounts of noise and outliers, but introduces a significant performance degradation. In this paper we first identify the reasons for this performance degradation and propose a hybrid optimization system that combines a Simulated Annealing search along with the standard Sparse ICP, in order to solve the underlying optimization problem more efficiently. We also provide several insights on how to further improve the overall efficiency by using a combination of approximate distance queries, parallel execution and uniform subsampling. The resulting method provides cumulative performance gain of more than one order of magnitude, as demonstrated through the registration of partially overlapping scans with various degrees of noise and outliers.
The reassembly of fractured 3D objects from their parts is an important problem in cultural herit... more The reassembly of fractured 3D objects from their parts is an important problem in cultural heritage and other domains. We approach reassembly from a geometric matching perspective and propose a pipeline for the automatic solution of the problem, where an efficient and generic three-level coarse-to-fine search strategy is used for the underlying global optimization. Key to the efficiency of our approach is the use of a discretized approximation of the surfaces’ distance field, which significantly reduces the cost of distance queries and allows our method to systematically search the global parameter space with minimal cost. The resulting reassembly pipeline provides highly reliable alignment, as demonstrated through the reassembly of fractured objects from their fragments and the reconstruction of 3D objects from partial scans, showcasing the wide applicability of our methodology.
In this paper we present a novel generic method for the fast and accurate computation of geometri... more In this paper we present a novel generic method for the fast and accurate computation of geometric features at multiple scales. The presented method works on arbitrarily complex models and operates in the parametric space. The majority of the existing methods compute local features directly on the geometric representation of the model. Our approach decouples the computational complexity from the underlying geometry and in contrast to other parametric space methods, it is not restricted to a specific feature or parameterization of the surface. We show that the method performs accurately and at interactive rates, even for large feature areas of support, rendering the method suitable for animated shapes.
The reassembly of fractured 3D objects is a critical problem in computational archaeology, and ot... more The reassembly of fractured 3D objects is a critical problem in computational archaeology, and other application domains. An essential part of this problem is to distinguish the regions of the object that belong to the original surface from the fractured ones. A general strategy to solve this region classification problem is to first divide the surface of the object into distinct facets and then classify each one of them based on statistical properties. While many relevant algorithms have been previously proposed, a comparative evaluation of some well-known segmentation strategies, when used in the context of such a problem, is absent from the bibliography. In this poster we present our ongoing work on the evaluation of the performance and quality of segmentation algorithms when operating on fractured objects. We also present a novel method for the classification of the segmented regions to intact and fractured, based on their statistical properties.
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Papers by Anthousis Andreadis