Matteo Dellepiane

Global refinement of image-to-geometry registration for color projection on 3D models

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.

Integration and Analysis of Sampled Data: Visualization Approaches and Platforms

The evolution of digitization technologies (2D and 3D) and the consequent wide availability of digital representations of artworks has ignited a number of works aimed at providing tools and platforms for archival, visual presentation, and integration of all those media. This chapter reviews some available instruments, focusing first on the platforms that could support the CH/DH professional in the single or cross-analysis of multimedia representations. Then, we discuss the available approaches for structuring and integrating the available data, presenting both the GIS-based solutions and the more recent Web-based systems. Some discussion on open issues concludes the contribution.

From Paper to Web: Automatic Generation of a Web-Accessible 3D Repository of Pottery Types

3D web repositories are a hot topic for the research community in general. In the Cultural Heritage (CH) context, 3D repositories pose a difficult challenge due to the complexity and variability of models and to the need of structured and coherent metadata for browsing and searching. This paper presents one of the efforts of the ArchAIDE project: to create a structured and semantically-rich 3D database of pottery types, usable by archaeologists and other communities. For example, researchers working on shape-based analysis and automatic classification. The automated workflow described here starts from pages of a printed catalog, extracts the textual and graphical description of a pottery type, and processes those data to produce structured metadata information and a 3D representation. These information are then ingested in the database, where they become accessible by the community using dynamically-created web presentation pages, showing in a common context: 3D, 2D and metadata information. CCS Concepts •Computer Graphics → Shape modelling; •Data management systems → Database design and models; •Document management and text processing → Document capture;

The Dream and the Cross: a 3D-referenced, web-based digital edition

The Dream of the Rood is one of the earliest Christian poems in the corpus of Old English literature, and an example of the genre of dream poetry. While its complete text can be found in the 10th Century ”Vercelli Book”, the poem is considerably older, and its oldest occurrence is carved (in runes) on the 7-8th Century Ruthwell Stone Cross. In this paper, we present the prototype of a web-based digital edition of the Dream of the Rood, as it appears on the Ruthwell Cross. The multimedia framework presents the highly detailed 3D model acquired with 3D Scanning technology, together with the transcription and translation of the runes that can be found on its surface. The textual and spatial information are linked through a system of bi-directional links called spots, that give the possibility to the user to have a free navigation over the multimedia content, keeping the 3D and textual data synchronized. The proposed work provides discussion and solution on two main issues related to digital editions: the integration of three dimensional content in the context of the presentation on the web platform of heterogeneous multimedia data, and the creation of an XML encoding that could account for the necessities of 3D data disposition, but keeping the encoding rules in the context of the standards of the community.

Improving High-Speed Scanning Systems by Photometric Stereo

High-speed scanning systems can be extremely valuable for Cultural Heritage applications, especially when large collections of small objects have to be acquired. However, fine details may not be acquired using this technology. Nevertheless, it is possible to try to recover them by taking advantage of the additional data provided by these systems: the calibrated video sequence of the acquisition, and the position of the projector light for each frame. In this paper, we propose a workflow that processes the video sequence with a photometric stereo approach, in order to refine the coarse geometry provided by the scanner. A normal map is first extracted by a method that accounts for the unevenly distributed sampling that generally results from the particular trajectory followed by this kind of scanners during the acquisition. This normal map is then integrated in order to recover missing geometric features. Good performances are achieved, since the whole workflow is particularly suited to GPU programming.