Computer tools for depicting shape and detail in 3D archaeological models

Posted on August 24, 2016


On every Wednesday I post videos of a session I have filmed at a conference.

Session Abstract:

Miguel Carrero-Pazos, Alia Vázquez-Martínez, Benito Vilas-Estévez, Miguel Busto-Zapico
Archaeology has been long characterized by the interdisciplinarity and the transversality of their approaches and methodologies. In this context, we strongly believe that a proposal of a session that considers the use of the New Technologies (NNTT) on the fields that deal with computer tools for depict shape and detail in 3D archaeological models, and their application in archaeology is necessary. At the same time, we might see the impact that other sciences could have into Archaeology and how it is seen through them. In the field of archaeological research, the use of the NNTT are widely spread due to their technical profits, as quicker methodologies to obtain archaeological data or carrying out some analysis that will be impossible to conduct manually. We should not forget that the use of these techniques allow us to get greater objectification of the archaeological record. From this perspective, the possibilities of the application of the NNTT to Archaeology are almost unlimited. In this sense, since its beginning, Processual and Post-processual Archaeology has been joining the benefits of the computer science advancements. Therefore, we are able to consider a strong consolidated research field. Since the beginning of Informatics’ Era, different branches of archaeological research have been arisen. One of them has been the representation and study of archaeological elements by their virtual reconstruction (3D). From this view, different approaches have appeared, especially since the turn of the century, which put the attention on the development of visual techniques to implement archaeological 3D models. That is particularly the case regarding the Polynomial Texture Mapping technique, from RTI methodology -Reflection Transformation Imaging- (Malzbender et al., 2001). Or its counterpart, the virtual RTI, which combines reflection transformation techniques with photogrammetry and no intrusive digitalization, in order to create an advanced level of interaction with the 3D model, and to enhance the topographic surface (Earl, Beale, Martinez, Pagi, 2010). Moreover, the Morphological Residual Model (MRM), a recent technique (currently inaccessible) which also enables a better visualization of 3D model details has to be denoted (Pires et al., 2014; Correia Santos et al., 2014; Correia Santos et al., 2015; Pires et al., 2015). On the other hand, with the development of free and open access software like Meshlab, it has been multiplied the contributions to the creation of rendering plugins (or shaders), which analyse some characteristics of the 3D model to enhance them. Perhaps one of the most relevant is the Radiance Scaling (Vergne et al., 2010), an expressive rendering which enhance the 3D model concavities and convexities. The application of these techniques to the study of archaeological objects and structures is not new, but it has been steadily increasing since the last decade. Everything that has been said before show us the framework or context in which our session will take place. Our aim is to show different examples of 3D visual techniques, which have been planned or developed to use with computer tools. In this sense, we will be able to reflect about the advantages and the challenges of the interdisciplinarity and the transversality of our discipline and the use of NNTT in Archaeology. Nowadays the NNTT are a fundamental part of the development of the archaeological research. In many cases, the future of our discipline is to adapt and absorb new methods and models developed in other scientific fields. The purpose of our meeting will be to learn from those so heterogeneous experiences, and show how the use of other techniques can help Archaeology to plan and resolve different archaeological problems. Communications, posters and audio-visual material will be accepted, especially those that deal with new computer techniques, to depict shape and detail in 3D archaeological models.
[References] CORREIA SANTOS, M. J., PIRES, H., SOUSA, O., 2014, “Nuevas lecturas de las inscripciones del santuario de Panóias (Vila Real, Portugal)”, Sylloge Epigraphica
Barcinonensis (SEBarc) XII, Barcelona, pp. 197-224. CORREIA SANTOS, M. J., SOUSA, O., PIRES, H., FONTE, J., GONÇALVES-SECO, L., 2015, “Travelling back in Time to Recapture Old Texts. The use of Morphological Residual Model (M.R.M.) for epigraphic reading: four case studies (CIL 02, 02395a, CIL 02, 02395c, CIL 02, 02476, CIL 02, 05607)”, In Acts of Information Technologies for Epigraphy and Cultural Heritage. Proceedings of the first EAGLE International Conference, Europeana Eagle project. Studi umanistici- Antichistica, Sapienza Universitá Editrice, pp. 437-450. EARL, G., BEALE, G., MARTINEZ, K., PAGI, H., 2010, “Polynomial Texture Mapping and Related Imaging Technologies for the Recording, Analysis and Presentation of Archaeological Materials”. In International Society for Photogrammetry and Remote Sensing, vol. XXXVIII, Part 5, pp. 218-223. MALZBENDER, T., WILBURN, B., GELB, D., AMBRISCO, B., 2006, “Surface enhancement using real-time photogrammetric stereo and reflectance transformation”. In Eurographics Symposium on Rendering, pp. 245-250. PIRES, H., FONTE, J., GONÇALVES-SECO, L., CORREIA SANTOS, M. J., SOUSA, O., 2014, Morphological Residual Model. A Tool for Enhancing Epigraphic Readings of Highly Erosioned Surfaces, EAGLE- Information Technologies for Epigraphy and Cultural Heritage in the Ancient World. Paris, pp. 133-144. PIRES, H., MARTÍNEZ RUBIO, J., ELORZA ARANA, A., 2015, “Techniques for revealing 3D hidden archaeological features: morphological residual models as a virtual-polynomial texture maps”, The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, volumen XL-5/W4, 2015 3D Virtual Reconstruction and Visualization of Complex Arquitectures, 25-27 February 2015, Avila, Spain, pp. 415-421. VERGNE, R., VANDERHAEGUE, D., CHEN, J., BARLA, P., GRANIER, X., SCHILICK, C., 2011, “Implicit brushes for stylized line-based rendering”, Computer Graphics Forum, 30 (2), pp. 513-522.

S06-01 Automated heritage monitoring software prototype implementing 3D technologies

Rimvydas Laužikas, Albinas Kuncevičius, Tadas Žižiūnas, Egidijus Žilinskas
Preservation of urban heritage is one of the main challenges for contemporary society. It’s closely connected with several dimensions: Global-local rhetoric, cultural tourism, armed conflicts, immigration, cultural changes, investment flows, new transport infrastructures and etc. Nowadays very often organizations responsible for heritage management constantly have to deal with lack of resources, which are crucial for proper heritage preservation, maintaining and protection. Particularly it is problematic for countries with low GDP or unstable political situation. The possible solution of these problems could be automated heritage monitoring software system, based on the 3D technologies. The system prototype was developed and tested by Vilnius University and Terra Modus Ltd. in frame of project “Creation of automated urban heritage monitoring software prototype”. Project financed by Lithuanian Council for Culture. At this paper will present the main results of the project. 3D scanning technology is the most accurate method to capture the situation of an evolving cultural heritage object or complex at a given time. As a cultural heritage object or complex is evolving continuously, two 3D point clouds created at different time allow to reliably trace potential changes. Monitoring of large scale heritage complexes such as urban heritage objects is a resource demanding task and in such cases automatic computer-based 3D visual analysis is appropriate. Comparison of 3D visual data captured in different time advances to next level when utilizing methods of 3D photogrammetry which make it possible (at least partially) to create 3D point clouds from old photos, giving us opportunities to expand research by adding empirical data captured before 3D scanning equipment and also lowering costs to conduct such research.

S06-02 A machine learning approach for 3D shape analysis and recognition of archaeological objects
Diego Jiménez-Badillo, Mario Canul Ku, Salvador Ruíz-Correa, Rogelio Hasimoto-Beltrán
Museum professionals all over the world have always shown great interest in acquiring automatic methods to register and analyse the shape of cultural heritage artefacts. Thanks to recent advances in 3D scanning and photogrammetry techniques, it is now possible to model the surface of objects with very little effort and in a relatively short time. The continuous adoption of these techniques in cultural institutions has generated thousands if not millions of 3D digital models. Unfortunately, after these resources are produced, very little effort is spent in making them accessible to researchers or the general public. Part of the problem is a lack of efficient computer mechanisms to search, retrieve and classify 3D data. The conventional way to search and retrieve 3D models consists in composing a query based on text descriptions. However, textual annotations are necessarily constrained by the database application domain, ontology, etc., as well as by language and other factors. Consequently they are inadequate for shape oriented searches. This paper presents results of an on-going project focused on developing a computer platform to automatize the search, retrieval, recognition and analysis of 3D object models. The platform processes queries based on geometric properties instead of text. Simply stated, the computer program takes a 3D surface mesh as input (i.e. the query model). Then, a search engine compares it to hundreds or even thousands of 3D scanned objects stored in a repository identifying those that approximate the shape of the query model. Next, the matching models are retrieved, ranked by degree of similarity and displayed to the final user. Afterwards, additional tools can be deployed to perform some kind of analysis on the objects retrieved. A platform like this is much more powerful than a text search engine because it avoids mismatching situations, such as when a person queries the database looking up for “bowls” and retrieves nothing just because the bowls are labelled as “cuencos” (a Spanish term) or “cajetes” (i.e. a term common in Mesoamerican archaeology to described the same type of vessels). Moreover, the platform is able to exploit mathematical analysis algorithms for automatic classification of shapes. During the presentation, we discuss the specific requirements that a shape recognition platform must satisfy to be useful in museums and cultural heritage research. In archaeological projects, for example, we encounter objects that are not necessarily identical in terms of geometry and yet they are considered to belong to the same class. We also intent to show the first part of this platform, namely the search engine for matching and retrieval of 3D Objects.

S06-04 Application of Computer Vision algorithms for automatic classification of archaeological artefacts
Edgar Francisco Román-Rangel, Diego Jiménez-Badillo
The application of computer vision technologies for the analysis of cultural heritage artefacts has witnessed a rapid growth during the last decade. This is especially true with regard to the creation and use of digital 3D models, which enable capabilities that would not be available using the original artefacts, such as automatic and semi-automatic content analysis, virtual reconstructions, more efficient archiving, sharing documentation online, training of novel scholars, etc. An area of especial interest is the statistical analysis of shape features observed on 3D models of artefacts, especially ceramic vessels and pottery sherds, with the purpose of categorizing and classifying objects in an automatic way. In this paper we present new results of an on-going project focused on applying computer vision techniques for automatic classification of archaeological artefacts. We discuss some useful approaches that involve the extraction of shape descriptors (SIFT, Spin Images, etc.) within a Bag of Visual Words model and propose a novel technique for local description of 3D surfaces called Histogram of Spherical Orientations (HoSO). The HoSO local descriptor consists of the quantization of the local orientations of a point with respect to its nearest neighbours. Such local orientations are computed both in the azimuth and the zenith axes. The frequencies of the local orientations are stored in a histogram, which can then be used for comparison and matching purposes

S06-05 A comparison of methods for creating 3D models of obsidian artifacts
Samantha Thi Porter, Kele Missal
Within the discipline of lithic analysis, digital 3D artifact models are useful both as a means of augmenting traditional two-dimensional representations, and as a form of raw data for morphometric and technological analysis. Unfortunately, some raw materials are inherently more difficult to capture than others. Obsidian, specifically, is highly reflective, tends to have a visually homogenous surface, and is oftentimes transparent. All of these factors restrict a researcher’s ability to capture images of obsidian objects that are of high enough quality for the construction of an accurate 3D model. In some parts of the world the vast majority of lithic artifacts are made of obsidian. Therefore, finding a way to systematically model obsidian artifacts with a high degree of precision would be extremely useful.
We compare the effectiveness of two different methods of capturing object morphology, (structured- light scanning using a DAVID SLS-2 system and close-range photogrammetry using the software Agisoft PhotoScan) in conjunction with several commonly used substances used to coat lithic artifacts for scanning, (brushed-on talc powder, talc-based developer spray, and chalk spray) on a sample of experimentally produced obsidian pieces of different shapes and sizes. Coatings are evaluated on their ease of use, the quality of scans that result from their use, and their impact on artifacts (e.g. difficulty of removal, and effects on artifact labels). The quality of the 3D models are evaluated on the accuracy of gross artifact morphology as well as success in capturing fine features commonly used in lithic analysis such as retouch, platform preparation removals, ripples, and lancets. We also discuss alternative methods of documenting obsidian artifacts that do not necessitate coating, such as Reflectance Transformation Imaging (RTI).
S06-06 Les gestes retrouves: A 3D visualisation approach to the functional study of Early Upper Palaeolithic grinding stones

Sorin Hermon, Laura Longo, Dante Abate, Giusi Sorrentino, Natalia Skakun
The paper will present an innovative approach to the identification and characterization of use-wear traces on Aurignacian grinding stones used to processed plant in order to get staple food. Such a study is essential in reconstructing ancient dietary habits of humans at a crucial stage of human colonization in Eurasia. The current study focuses on the potential contribution of 3D investigation, at various levels of detail and resolution, to the identification of such traces and residues. The working methodology is still under revision, but it includes the following steps, firstly applied on a grinding stone from the Upper Palaeolithic site of Surein, Crimean Peninsula:
1. An overall documentation of the grinding stone: 3D geometry and rectified macro-photography. 2. Rugosity analysis of the stone’s surface, in order to identify anomalies relatable to human intentional intervention (grinding). This analysis is performed using two approaches: cloud compare and Meshlab filter functions of colorizing curvatures (several tests are currently performed, using different curvature types). 3. 3D documentation of molds taken in selected areas on the active surface of the grinding stone. These were 3D scanned using a shuttered light scanner and photogrammetry. Values had to be inversed along the Z axis, in order to correctly represent the surface micro-topography. 4. Rectified digital images taken with a digital microscope at various magnifications, at logarithmic steps from x25 to x2500. These were assembled together in a CAD system, each magnification being considered one layer, in order to create a mosaicking of the surface. 5. Measurements of the area of trace marks and characterization of their shape. Clustering of these marks along the working surface of the stone and associated starches.
Overall, more than 40 trace marks were observed and characterized. The rugosity analysis of the working surface of the grinding stone correctly identified areas that have been modified by intentional human intervention. The presence of wear-traces and adhering starches, identified under microscope, along with morphological characteristic of use marks, are among the earliest evidences for plant processing at the dawn of modern humans in Eurasia. Currently, other 10 stones related to plant grinding (both grinding stones and pestles) are under analysis, with very promising preliminary results. The integration of 3D documentation, macro-photography and digital microscopy provided an ideal set of 3D and 2D data that has been successfully used for the functional analysis of Aurigancian grinding stones.

S06-10 From survey to 3D modeling to 3D printing: Bramante’s Nymphaeum Colonna at Genazzano

Tommaso Empler, Adriana Caldarone
Today it’s more and more widespread the use of new computer techniques applied to the field of archeology. Techniques are often heterogeneous, but organized in a right pipeline allow a good understanding of the archaeological heritage. In the study of the “Nymphaeum Colonna of Genazzano”, attributed to Bramante, the integrated approach of systems such as photogrammetry, 3D modeling, virtual tour and 3D printing, allows to generate a scale model, with low margins of error, of the shape of the Nymphaeum at the beginning of the sixteenth century (researches until now were very limited). Initial activities are concentrated in the acquisition of data using a total station or TST (total station theodolite) and photographs, taken as multiple frames, recognizable in the coordinate system result from the survey with TST. A special software allows the georeferencing of the raster files with the captured data, allowing the generation of bitmap textures, used in the next step of 3D modeling and rendering. At this stage of 3D visualization it’s possible to spot the differences between the Nymphaeum in the project of Bramante and the current status. The following step goes from the virtual 3D model to prototyping, through the realization of a real object by a 3D printing. The object, printed in two PLA parts, is then cleaned by the support materials and joined together. The methodology described revolutionizes and increases the “empathetic size” with the archaeological site, with its use, giving the opportunity to be better perceived either in its current state either in the historical reconstruction at the time of Bramante.
S06-11 3D Reconstruction of Koch, Russian rowing/sailing boat of the 17th century
Mikhail V. Vavulin, Olga V. Zaytceva, Andrei A. Pushkarev
Koch is a Russian rowing/sailing boat adapted for the heavy Arctic conditions. A virtual 3D reconstruction of a 17th-century koch commenced in 2014. Precise engineering drawings were unknown to Russian boat makers of the 17th century, while the few pictures of koch and inconsistent written sources do not allow for an authentic reconstruction of all details and specific features of the vessel. The original boat parts discovered during archaeological studies in Mangazeya, the first transpolar Russian town in Siberia, served the unique resource for the reconstruction. The area had no forests to provide wood for construction, so houses were built from dismantled boats. Structures built entirely from framings were surveyed in Mangazeya. Boat parts are perfectly preserved in the cultural layer of permafrost. For the purposes of reconstruction, we used the two best preserved koch framings dating back to the 17th century. We needed to perform 3D scanning of 293 boat parts. Those parts represented individual pieces of various forms and sizes (from 0.3 m to 5.6 m). This diversity was the key factor when choosing the equipment and elaborating scanning methods. We used scanners GoScan 3D and GoScan 50 by Creaform with the optimal resolution of 1 mm. Textures were identified using photo camera Nikon D700 and the SfM (structure from motion) 3D model technique. Agisoft Photoscan Pro software was used to create low-poly models with applied textures. We used Geomagic Wrap software to perform the final processing of the scanned model and to copy the textures from low to high poly. 3D Studio max software was used to reproduce the original look of the parts by removing traces of secondary use and natural wood deformation. The same software was used for virtual assembly of the parts and 3D reconstruction of the whole boat.

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