New Reflection Transformation Imaging Methods for Rock Art and Multiple-Viewpoint Display

info:eu-repo/semantics/publishedVersio

Reflectance Transformation Imaging (RTI) System for Ancient Documentary Artefacts

This tutorial summarises our uses of reflectance transformation imaging in archaeological contexts. It introduces the UK AHRC funded project reflectance Transformation Imaging for Anciant Documentary Artefacts and demonstrates imaging methodologies

Methodological considerations of integrating portable digital technologies in the analysis and management of complex superimposed Californian pictographs: From spectroscopy and spectral imaging to 3-D scanning

How can the utilization of newly developed advanced portable technologies give us greater understandings of the most complex of prehistoric rock art? This is the questions driving The Gordian Knot project analysing the polychrome Californian site known as Pleito. New small transportable devices allow detailed on-site analyses of rock art. These non-destructive portable technologies can use X-ray and Raman technology to determine the chemical elements used to make the pigment that makes the painting; they can use imaging techniques such as Highlight Reflective Transformation Imaging and dStretch© to enhance their visibility; they can use digital imagery to disentangle complex superimposed paintings; and they can use portable laser instruments to analyse the micro-topography of the rock surface and integrate these technologies into a 3-D environment. This paper outlines a robust methodology and preliminary results to show how an integration of different portable technologies can serve rock art research and management

A Novel Framework for Highlight Reflectance Transformation Imaging

We propose a novel pipeline and related software tools for processing the multi-light image collections (MLICs) acquired in different application contexts to obtain shape and appearance information of captured surfaces, as well as to derive compact relightable representations of them. Our pipeline extends the popular Highlight Reflectance Transformation Imaging (H-RTI) framework, which is widely used in the Cultural Heritage domain. We support, in particular, perspective camera modeling, per-pixel interpolated light direction estimation, as well as light normalization correcting vignetting and uneven non-directional illumination. Furthermore, we propose two novel easy-to-use software tools to simplify all processing steps. The tools, in addition to support easy processing and encoding of pixel data, implement a variety of visualizations, as well as multiple reflectance-model-fitting options. Experimental tests on synthetic and real-world MLICs demonstrate the usefulness of the novel algorithmic framework and the potential benefits of the proposed tools for end-user applications.Terms: "European Union (EU)" & "Horizon 2020" / Action: H2020-EU.3.6.3. - Reflective societies - cultural heritage and European identity / Acronym: Scan4Reco / Grant number: 665091DSURF project (PRIN 2015) funded by the Italian Ministry of University and ResearchSardinian Regional Authorities under projects VIGEC and Vis&VideoLa

Relighting Egyptian rock art : rapid, accurate HD imaging of prehistoric petroglyphs

Within the framework of the project “Tracing Palaeolithic Aurochs: Rock Art Survey in Upper Egypt”, financed by the National Geographic Society, the authors participated in the long standing tradition of Belgian rock art research in Egypt. Under the direction of Dr. Dirk Huyge, extensive stretches of rock formations along wadi’s in the Eastern Desert between Edfu and Kom Ombo were surveyed in October-November 2014 for the presence of more prehistoric rock art sites, similar to the ones already discovered and studied by the Belgian team in this same region at Qurta and el-Hosh (Huyge et al 2007, 2011, 2012; Huyge 2009). This contribution focuses uniquely on a new component introduced to the 2014 mission: the development and testing of HD imaging techniques for rapid and accurate field recording of the sites with petroglyphs. Multi-light reflectance and 3D photogrammetry techniques were tested on their reliability and operability for a survey in the field

On-the-Go Reflectance Transformation Imaging with Ordinary Smartphones

Reflectance Transformation Imaging (RTI) is a popular technique that allows the recovery of per-pixel reflectance information by capturing an object under different light conditions. This can be later used to reveal surface details and interactively relight the subject. Such process, however, typically requires dedicated hardware setups to recover the light direction from multiple locations, making the process tedious when performed outside the lab. We propose a novel RTI method that can be carried out by recording videos with two ordinary smartphones. The flash led-light of one device is used to illuminate the subject while the other captures the reflectance. Since the led is mounted close to the camera lenses, we can infer the light direction for thousands of images by freely moving the illuminating device while observing a fiducial marker surrounding the subject. To deal with such amount of data, we propose a neural relighting model that reconstructs object appearance for arbitrary light directions from extremely compact reflectance distribution data compressed via Principal Components Analysis (PCA). Experiments shows that the proposed technique can be easily performed on the field with a resulting RTI model that can outperform state-of-the-art approaches involving dedicated hardware setups

considerations on the use of digital tools for documenting ancient wall graffiti

Abstract. Ancient graffiti are a valuable and constant historical evidence through the human history, regardless from the geographic area or historical period. They can be found on different kinds of surfaces and in different contexts, such as religious building or civic structures, in public or private environments. Their study and comprehension need to be grounded on good and complete documentation techniques. The application of accurate recording methods is even more important for ancient graffiti, for a series of reasons. First of all, their perception is often less immediate than other historical or artistic evidence, and directly depends on external aspects, such as the lighting conditions, and personal skills. Moreover, their interpretation is often challenging also for expert scholars, so as to require both the most objective reproduction possible and the personal interpretation of the scholar. As a case study, several late medieval graffiti scratched on frescos have been documented with digital methods. Results will be presented and discussed. This paper will mainly focus on graffiti scratched on frescos or plaster, and not on petroglyphs, i.e. marks and drawings on rock surfaces.</p

Digital imaging techniques for recording and analysing prehistoric rock art panels in Galicia (NW Iberia)

Several works have highlighted the relevance of 3D modelling techniques for the study of rock art, especially in case of deteriorated state of preservation. This paper presents a methodological approach to accurate document two Bronze Age rock art panels in Galicia (Spain), using photogrammetry SfM. The main aim is to show the application of digital enhancement techniques which have allowed the accurate depiction of the motifs and the correction of previous calques, focusing on the application of the exaggerated shading as a novel analytical method