@article {irs17-12, title = {Analysis of a multi-ring technique for 3D pattern recognition}, number = {17-12}, year = {2017}, month = {June}, pages = {20 p.}, publisher = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

Pattern characterization of geometric features is of great interest in the cultural heritage domain, as the style of the some parts such beards, hairs, helms or cuirass decorations would support and enhance the classification and/or cataloguing of the archaeological artefacts and fragments. In this context, a pattern is a geometric or colour feature which is repeated over a surface, either on its entirety or on a part (for instance, engravings and chisellings, ornamental decorations, etc.). In the literature, methods that face this problem either project the surface into an image and then adopt a image pattern recognition techniques or try to extend in 3D an existing image technique to surfaces. In this paper, we analyse the performance of the technique called mesh Local Binary Pattern (meshLBP) that works on triangulation meshes, considering implementation defined in [WTBdB15, WBdB15] and freely available. Tests are performed on meshes of the repository at STARC - The Cyprus Institute [STA] that correspond to laser scans of earthenware fragments retrieved from the Salamina Island. Fragments are represented with triangulations, not necessarily uniformly sampled. In this paper we analyse two kind of patterns represented by geometric and colorimetric variations on the surface of the fragment. In addition, we discuss a sub-sample strategy to keep the effectiveness of the meshLBP descriptor and the dependence of the operator on parameters such as the surface representation and the number of rings used for its multi-scale evaluation. Finally, the main limitations of the method are discussed and possible improvements and future developments are outlined.

}, keywords = {3D pattern analysis, 3D pattern classification, mesh}, url = {http://irs.imati.cnr.it/reports/irs17-12}, author = {E. Moscoso Thompson and S. Biasotti} } @article {ipa|Calcolo di descrittori ibridi geometria-colore per l{\textquoteright}analisi di similarit{\`a} di forme 3D|2016, title = {Calcolo di descrittori ibridi geometria-colore per l{\textquoteright}analisi di similarit{\`a} di forme 3D}, year = {2016}, month = {June}, pages = {24 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

Il riconoscimento e la classificazione di forme geometriche hanno molteplici applicazioni in grafica computazionale, spaziando dallo sviluppo di search engine all{\textquoteright}identificazione di anomalie in modelli medicali orientati al paziente, al design di nuovi farmaci e alla sperimentazione in silico. In tutti questi contesti, il confronto tra forme viene tradotto nel confronto tra descrizioni dell{\textquoteright}oggetto. {\`E} quindi di fondamentale importanza che una buona descrizione dell{\textquoteright}oggetto sia quanto pi{\`u} possibile completa, per risultare univoca, e allo stesso tempo concisa, per poter essere facilmente computabile e confrontabile con altre descrizioni. Inoltre, la descrizione geometrica di un oggetto 3D pu{\`o} essere corredata da informazioni colorimetriche, eventuali annotazioni e/o dati derivanti dalla sua acquisizione/provenienza. Nell{\textquoteright}ambito generale del confronto di forme 3D, in questo lavoro si analizza un metodo che utilizza propriet{\`a} geometriche e colorimetriche. Rispetto alla implementazione presente nella letteratura, si studia una ottimizzazione del metodo volta a diminuirne la complessit{\`a} computazionale e di memoria, e si discutono possibili strategie per un futuro miglioramento.

}, keywords = {Hybrid geometry-colour shape description}, url = {http://irs.imati.cnr.it/reports/irs16-05}, author = {S. Biasotti and A. Raffo} } @article {ipa|Comparing methods for the approximation of rainfall fields in environmental applications|2016, title = {Comparing methods for the approximation of rainfall fields in environmental applications}, year = {2016}, month = {February}, pages = {26 p.}, institution = {CNR-IMATI}, address = {Genova}, abstract = {

Digital environmental data are becoming commonplace and the amount of information they provide is huge, yet complex to process, due to the size, variety, and dynamic nature of the data captured by sensing devices. The paper discusses an evaluation framework for comparing methods to approximate observed rain data, in real conditions of sparsity of the observations. The novelty brought by this experimental study stands in the geographical area and heterogeneity of the data used for evaluation, aspects which challenge all approximation methods. The Liguria region, located in the north-west of Italy, is a complex area for the orography and the closeness to the sea, which cause complex hydro-meteorological events. The observed rain data are highly heterogeneous: two data sets come from measured rain gathered from two different rain gauge networks, with different characteristics and spatial distribution over the Liguria region; the third data set come from weather radar, with a more regular coverage of the same region but a different veracity. Finally, another novelty of the paper is brought by the proposal of an application-oriented perspective on the comparison. The approximation models the rain field, whose maxima and their evolution is essential for an effective monitoring of meteorological events. Therefore, we adapt a storm tracking technique to the analysis of the displacement of maxima computed by the different methods.

}, keywords = {Surface approximation}, url = {http://irs.imati.cnr.it/reports/irs16-10}, author = {G. Patan{\'e} and A. Cerri and V. Skytt and S. Pittaluga and S. Biasotti and D. Sobrero and T. Dokken and M. Spagnuolo} } @article {ipa|Feature curve identification in archaeological fragments using an extension of the Hough transform|2016, title = {Feature curve identification in archaeological fragments using an extension of the Hough transform}, year = {2016}, month = {July}, pages = {19 p.}, institution = {CNR-IMATI}, address = {Genova}, abstract = {

The use of computer graphics techniques in cultural heritage (CH) has led to impressive improvements in technologies related to digital acquisition and rendering of 3D CH data. Digitized artefacts are becoming widely available for access and reuse, thus increasing the need of tools able to support comparative shape analysis. As 3D artefacts are often worn, eroded and broken, these tools cannot take advantage of existing methods based on exact matching but they rather require new approaches able to identify partial features in portions of models thus leading to a double partiality of the matching problem, in terms of both features and models In this context, we propose a method based on a novel generalization of the Hough transform technique able to identify and localize semantic features like anatomical features, ornaments, or decorations on digital artefacts or fragments, even if the features are partially damaged or incomplete. The major advantages of using a method based on the Hough transform technique are the relative robustness to noise and the recognition power also in the case of partial features. Our experiments on digital models of real artefacts are encouraging and show the potential of the method, which can work on both 3D meshes and point clouds.

}, keywords = {Hough transform}, url = {http://irs.imati.cnr.it/reports/irs16-09}, author = {ML. Torrente and S. Biasotti and B. Falcidieno} } @article {ipa|Persistence-based tracking of rainfall field maxima|2016, title = {Persistence-based tracking of rainfall field maxima}, year = {2016}, month = {July}, pages = {16 p.}, institution = {CNR-IMATI}, type = {Working paper}, address = {Genova}, abstract = {

In this paper we propose a novel methodology for tracking the maxima of rainfall precipitation fields, whose changes in time may give interesting insights on the evolution of storms. Our approach is based on a topological analysis of rainfall data allowing for the extraction of the most prominent, and hence meaningful, rainfall field maxima. Then, an ad-hoc bottleneck matching is used to track the evolution of maxima along multiple time instances. The potential of our method is exhibited through a set of experiments carried out on a collection of observed punctual rainfall data and radar measurements provided by Genova municipality and Regione Liguria.

}, keywords = {Storm tracking}, url = {http://irs.imati.cnr.it/reports/irs16-11}, author = {D. Sobrero and A. Cerri and S. Biasotti and S. Pittaluga and M. Spagnuolo} }