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

Satellite-based sunshine duration for Europe

In this study, two different methods were applied to derive daily and monthly sunshine duration based on high-resolution satellite products provided by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility on Climate Monitoring using data from Meteosat Second Generation (MSG) SEVIRI (Spinning Enhanced Visible and Infrared Imager). The satellite products were either hourly cloud type or hourly surface incoming direct radiation. The satellite sunshine duration estimates were not found to be significantly different using the native 15-minute temporal resolution of SEVIRI. The satellite-based sunshine duration products give additional spatial information over the European continent compared with equivalent in situ-based products. An evaluation of the satellite sunshine duration by product intercomparison and against station measurements was carried out to determine their accuracy. The satellite data were found to be within ±1 h/day compared to high-quality Baseline Surface Radiation Network or surface synoptic observations (SYNOP) station measurements. The satellite-based products differ more over the oceans than over land, mainly because of the treatment of fractional clouds in the cloud type-based sunshine duration product. This paper presents the methods used to derive the satellite sunshine duration products and the performance of the different retrievals. The main benefits and disadvantages compared to station-based products are also discussed

Image registration algorithm for molecular tagging velocimetry applied to unsteady flow in Hele-Shaw cell

In order to develop velocimetry methods for confined geometries, we propose to combine image registration and volumetric reconstruction from a monocular video of the draining of a Hele-Shaw cell filled with water. The cell’s thickness is small compared to the other two dimensions (e.g. 1x400 x 800 mm3). We use a technique known as molecular tagging which consists in marking by photobleaching a pattern in the fluid and then tracking its deformations. The evolution of the pattern is filmed with a camera whose principal axis coincides with the cell’s gap. The velocity of the fluid along this direction is not constant. Consequently, tracking the pattern cannot be achieved with classical methods because what is observed is the integral of the marked molecules over the entire cell’s gap. The proposed approach is built on top of direct image registration that we extend to specifically model the volumetric image formation. It allows us to accurately measure the motion and the velocity profiles for the entire volume (including the cell’s gap) which is something usually hard to achieve. The results we obtained are consistent with the theoretical hydrodynamic behaviour for this flow which is known as the Poiseuille flow

Study of the model-order reduction of the aerolastic behavior of a wing

The  ultimate goal of this project is to construct a   reduced-order model capable of  providing real-time predictions of   the aeroelastic behavior of a wing.  The approach for carrying out such a task is, firstly, in the spirit of classic modal analysis, to project the full-order, governing equations of the wing (finite element equations, for instance) onto the low-dimensional subspace spanned by a few global displacement modes. Such displacement modes, in turn, are obtained by applying data compression algorithms  to a representative set of full-order simulations.   Once these dominant displacement modes have been identified, the next step in the approach is to choose, among all points of the underlying finite element mesh,  a set of sampling points  so that the integrals appearing in the weak form of the balance equation can be accurately evaluated by monitoring the strains and stresses only at such key points.The main objective of this paper is to apply the model-order reduction technique to an airplane’s wing in order to speed up development of aircrafts or to get real-time results of a plane structural state. However, this case is especially complex since the wings are an aeroelastic problem where both fluid and structure must be computed in order to get realistic results. In order to improve the overall airplane design speed -in addition to the usage of MOR techniques- a complementary software has been developed. This is a parametric software capable of quickly generating a geometry and exporting it to simulate both the fluid and the structure with a FE software like Kratos. This software will be open sourced. The usage of the custom software helps to generate geometries that differ only on a single design parameter (the angle of attack in this paper). These different geometries are then processed with Kratos to obtain the high-fidelity result from each one of them. Once the high-fidelity snapshots have been obtained (five are used in this paper), the reduced order models are generated using a discrete version of the Proper Orthogonal Decomposition (POD) called Single Value Decomposition (SVD). Finally, using the discrete empirical interpolation method (DEIM), it is possible to interpolate between the simulations and obtain the results of any intermediate state in less than a second without having to perform the full simulation. No physical model has been constructed to compute the fluid and only statistical methods are employed for that part. The results turned out to be very precise regarding the structure ROM; all the same, the only statistical approach to the fluid proved to be not ideal and the accuracy error remained around 15% for this part