Browsing by Author "Komar, Alexander"

Now showing 1 - 5 of 5
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    Motif-driven Retrieval of Greek Painted Pottery
    (The Eurographics Association, 2019) Lengauer, Stefan; Komar, Alexander; Labrada, Arniel; Karl, Stephan; Trinkl, Elisabeth; Preiner, Reinhold; Bustos, Benjamin; Schreck, Tobias; Rizvic, Selma and Rodriguez Echavarria, Karina
    The analysis of painted pottery is instrumental for understanding ancient Greek society and human behavior of past cultures in Archaeology. A key part of this analysis is the discovery of cross references to establish links and correspondences. However, due to the vast amount of documented images and 3D scans of pottery objects in today's domain repositories, manual search is very time consuming. Computer aided retrieval methods are of increasing importance. Mostly, current retrieval systems for this kind of cultural heritage data only allow to search for pottery of similar vessel's shape. However, in many cases important similarity cues are given by motifs painted on these vessels. We present an interactive retrieval system that makes use of this information to allow for a motif-driven search in cultural heritage repositories. We address the problem of unsupervised motif extraction for preprocessing and the shape-based similarity search for Greek painted pottery. Our experimental evaluation on relevant repository data demonstrates effectiveness of our approach on examples of different motifs of interests.
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    Real-Time Gaussian-Product Subdivision on the GPU
    (The Eurographics Association, 2021) Komar, Alexander; Preiner, Reinhold; Andres, Bjoern and Campen, Marcel and Sedlmair, Michael
    We propose a real-time technique for rendering Gaussian-Product subdivision surfaces. This is achieved by our real-time subdivision pipeline, able to accept the base of Gaussian-Product subdivision, that is, a covariance mesh, which extends regular base meshes by storing additional 3x3 covariance matrices per vertex. Our technique evaluates the non-linear limit subdivision surface by computing B-spline patches embedded in a 9-dimensional dual space, where the subdivision scheme becomes linear. We construct and evaluate these B-spline patches using real-time tessellation capabilities of current GPUs. We analyzed the performance of our technique on all supported subdivision levels, and provide an analysis of its visual quality and geometric accuracy.
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    Semi-automated Annotation of Repetitive Ornaments on 3D Painted Pottery Surfaces
    (The Eurographics Association, 2020) Lengauer, Stefan; Komar, Alexander; Karl, Stephan; Trinkl, Elisabeth; Sipiran, Ivan; Schreck, Tobias; Preiner, Reinhold; Spagnuolo, Michela and Melero, Francisco Javier
    The creation of drawings from the surface of painted pottery artifacts is an important practice in archaeological research and documentation. Traditional approaches include manual drawings using pen and paper, either directly on the physical surface, or from photographs, while more recent approaches are supported by photography or flattening of 3D digitized objects. Elaborate vase paintings, mostly showing figural scenes, often comprise ornamental decorations in secondary position or in the background, exhibiting repetitive patterns. We propose a tool supporting the creation of archaeological drawings with a semi-automatic extraction of ornamental surface sections, based on a combination of user-defined queries and self-similarity detection. Appropriate heuristics allow to detect the presence and positions of ornamental bands, a frequently occurring scheme, where ornamental primitives are evenly spaced along the tangential direction of a vessel's solid of revolution. Our interactive tool allows domain experts to efficiently select ornamental queries, and assess the quality of resulting similarity detections. First experiments with real world artifacts from ancient Greek and Peruvian cultures confirm the feasibility of the approach.
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    Sketch-Aided Retrieval of Incomplete 3D Cultural Heritage Objects
    (The Eurographics Association, 2019) Lengauer, Stefan; Komar, Alexander; Labrada, Arniel; Karl, Stephan; Trinkl, Elisabeth; Preiner, Reinhold; Bustos, Benjamin; Schreck, Tobias; Biasotti, Silvia and Lavoué, Guillaume and Veltkamp, Remco
    Due to advances in digitization technology, documentation efforts and digital library systems, increasingly large collections of visual Cultural Heritage (CH) object data becomes available, offering rich opportunities for domain analysis, e.g., for comparing, tracing and studying objects created over time. In principle, existing shape- and image-based similarity search methods can aid such domain analysis tasks. However, in practice, visual object data are given in different modalities, including 2D, 3D, sketches or conventional drawings like profile sections or unwrappings. In addition, collections may be distributed across different publications and repositories, posing a challenge for implementing encompassing search and analysis systems. We introduce a methodology and system for cross-modal visual search in CH object data. Specifically, we propose a new query modality based on 3D views enhanced by user sketches (3D+sketch). This allows for adding new context to the search, which is useful e.g., for searching based on incomplete query objects, or for testing hypotheses on existence of certain shapes in a collection. We present an appropriately designed workflow for constructing query views from incomplete 3D objects enhanced by a user sketch based on shape completion and texture inpainting. Visual cues additionally help users compare retrieved objects with the query. We apply our method on a set of relevant 3D and view-based CH object data, demonstrating the feasibility of our approach and its potential to support analysis of domain experts in Archaeology and the field of CH in general.
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    Visual Exploration of Cultural Heritage Collections with Linked Spatiotemporal, Shape and Metadata Views
    (The Eurographics Association, 2020) Lengauer, Stefan; Komar, Alexander; Karl, Stephan; Trinkl, Elisabeth; Preiner, Reinhold; Schreck, Tobias; Krüger, Jens and Niessner, Matthias and Stückler, Jörg
    The analysis of Cultural Heritage (CH) artefacts is an important task in the Digital Humanities. Increasingly, rich CH artefact data comprising metadata of different modalities becomes available in digital libraries and research data repositories. How- ever, the large amounts and heterogeneity of artefacts in these repositories compromise their accessibility for common domain analysis tasks, as domain researchers lack a structural overview of the spatial, temporal, and categorical traits of the artefacts in these collections. Still, researchers need to compare artefacts along different modalities, put them into context, and deal with possible uncertainties, subjectivities, or missing data. To date, many works support domain research via interactive visuali- sation. The majority relies primarily on visualisation of text and metadata including spatiotemporal, image and shape data. However, fewer consider these types of data in a tightly coupled way. We present an approach for tightly integrated multimodal visual exploration of large CH data collections along space, time and shape traits. Based on requirements obtained in collab- oration with domain researchers, we introduce a set of interlinked views for exploration of said modalities. An appropriately defined approach automatically computes most significant correlations across different modalities, guiding the user towards de- tecting interesting artefact relationships. We apply our approach to pertinent archaeological data collections, and demonstrate that characteristic explorative tasks are effectively supported and domain-relevant artefact relations can be discovered.