Machine-readable universal data format for bidirectional reflectance distribution function and BiRDview—An open-source web-based application for viewing and comparing bidirectional reflectance data

Modern studies of bidirectional reflectance distribution function (BRDF) and its applications using data and machine-driven science require formatting of BRDF data according to Findable, accessible, interoperable and reusable (FAIR) data principles. As a solution a FAIR universal BRDF file-format based on Java Script Object Notation (JSON) is proposed. JSON principles as well as file structure are explained and examples are given. Automatic validation of universal BRDF file format is realized with the help of JSON schema. Furthermore, the source code and accompanying documentation are presented in dedicated supporting material files. It is expected that after its wide adoption, the proposed BRDF file format will enhance collaboration between different research groups and benefit machine-driven science. The uptake is facilitated by introducing a BiRDview—a modern open-source web-based application for BRDF visualization.This work has been done in the frame of the projects 16NRM08 BiRD and 18SIB03 BxDiff, that have received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. The work has also been supported by the Academy of Finland Flagship Programme, Photonics Research and Innovation (PREIN), decision number: 320167

Sipuncula inhabiting the coral Oculina patagonica in the western Mediterranean Sea

Background: We analyzed the sipunculan fauna inhabiting the scleractinian coral Oculina patagonica in the Marine Reserve of Tabarca Island (western Mediterranean). Results: Five sipunculan species were collected from 2011 to 2014: Phascolosoma stephensoni, P. granulatum, P. cf. agassizii, Aspidosiphon misakiensis, and Golfingia vulgaris. All five species were reported for the first time inhabiting O. patagonica; with P. cf. agassizii being a new record for the Iberian Peninsula. The average abundance of sipunculans inhabiting the coral was 468.75 ± 158.04 ind m−2, representing the second most abundant taxonomic group, in biomass, after Mollusca. Conclusions: Sipunculan diversity was low comparing with tropical reefs, but species abundances were higher than in soft-bottom nearby areas and community structure appears to be more homogeneous. There may be a considerable contribution to the erosion of the coral skeleton by sipunculans

Introducción y presentación

Depto. de Ciencia Política y de la AdministraciónFac. de Ciencias Políticas y SociologíaTRUEpu

Visual sensor fusion for active security in robotic industrial environments

This work presents a method of information fusion involving data captured by both a standard CCD camera and a ToF camera to be used in the detection of the proximity between a manipulator robot and a human. Both cameras are assumed to be located above the work area of an industrial robot. The fusion of colour images and time of light information makes it possible to know the 3D localization of objects with respect to a world coordinate system. At the same time this allows to know their colour information. Considering that ToF information given by the range camera contains innacuracies including distance error, border error, and pixel saturation, some corrections over the ToF information are proposed and developed to improve the results. The proposed fusion method uses the calibration parameters of both cameras to reproject 3D ToF points, expressed in a common coordinate system for both cameras and a robot arm, in 2D colour images. In addition to this, using the 3D information, the motion detection in a robot industrial environment is achieved, and the fusion of information is applied to the foreground objects previously detected. This combination of information results in a matrix that links colour and 3D information, giving the possibility of characterising the object by its colour in addition to its 3D localization. Further development of these methods will make it possible to identify objects and their position in the real world, and to use this information to prevent possible collisions between the robot and such objects

Influencia del tamaño de pigmento en la distancia de detección del sparkle

XI Reunión Nacional de Óptica Día de la Luz; Facultad de Ciencias • Universidad de Salamanca 1 - 4 Septiembre, 2015; http://rno11.usal.es/programaSe diseñó un experimento psicofísico para evaluar la influencia del tamaño del pigmento de efecto en la distancia de detección del sparkle. Los resultados mostraron que a mayor tamaño de pigmento, mayor distancia de detección. Además, la correlación visual e instrumental (distancia de detección vs. grado de sparkle (SG)) sigue una relación lineal, sin embargo, no existe una relación lineal con el tamaño de pigmento: la distancia es máxima para un tamaño inferior al tamaño máximo.Peer Reviewe

Color characterization of coatings with diffraction pigments

Coatings with diffraction pigments present high iridescence, which needs to be characterized in order to describe their appearance. The spectral bidirectional reflectance distribution functions (BRDFs) of six coatings with SpectraFlair diffraction pigments were measured using the robot-arm-based goniospectrophotometer GEFE, designed and developed at CSIC. Principal component analysis has been applied to study the coatings of BRDF data. From data evaluation and based on theoretical considerations, we propose a relevant geometric factor to study the spectral reflectance and color gamut variation of coatings with diffraction pigments. At fixed values of this geometric factor, the spectral BRDF component due to diffraction is almost constant. Commercially available portable goniospectrophotometers, extensively used in several industries (automotive and others), should be provided with more aspecular measurement angles to characterize the complex reflectance of goniochromatic coatings based on diffraction pigments, but they would not require either more than one irradiation angle or additional out-of-plane geometries.European Metrology Research Programme (EMRP) (EMRP IND52); Comunidad de Madrid (SINFOTON-CM: S2013/MIT-2790); Ministerio de Economía y Competitividad (MINECO) (DIP2015-65814)

3D point cloud registration based on a purpose-designed similarity measure

This article introduces a novel approach for finding a rigid transformation that coarsely aligns two 3D point clouds. The algorithm performs an iterative comparison between 2D descriptors by using a purpose-designed similarity measure in order to find correspondences between two 3D point clouds sensed from different positions of a free-form object. The descriptors (named with the acronym CIRCON) represent an ordered set of radial contours that are extracted around an interest-point within the point cloud. The search for correspondences is done iteratively, following a cell distribution that allows the algorithm to converge toward a candidate point. Using a single correspondence an initial estimation of the Euclidean transformation is computed and later refined by means of a multiresolution approach. This coarse alignment algorithm can be used for 3D modeling and object manipulation tasks such as "Bin Picking" when free-form objects are partially occluded or present symmetries

Visibility of sparkle in metallic paints

For suitable illumination and observation conditions, sparkles may be observed in metallic coatings. The visibility of these sparkles depends critically on their intensity, and on the paint medium surrounding the metallic flakes. Based on previous perception studies from other disciplines, we derive equations for the threshold for sparkles to be visible. The resulting equations show how the visibility of sparkles varies with the luminosity and distance of the light source, the diameter of the metallic flakes, and the reflection properties of the paint medium. The predictions are confirmed by common observations on metallic sparkle. For example, under appropriate conditions even metallic flakes as small as 1 μm diameter may be visible as sparkle, whereas under intense spot light the finer grades of metallic coatings do not show sparkle. We show that in direct sunlight, dark coarse metallic coatings show sparkles that are brighter than the brightest stars and planets in the night sky. Finally, we give equations to predict the number of visually distinguishable flake intensities, depending on local conditions. These equations are confirmed by previous results. Several practical examples for applying the equations derived in this article are provided.European Metrology Research Programme (EMRP) Spanish Ministry of Economy and Competitiveness(DPI2011-30090-C02) Comunidad de Madrid (CM: S2013/MIT-2790). The EMRP is jointly funded by the EMRP participating countries within the European Association of National Meteorlogy (EURAMET) and the European Union

Accurate estimation of airborne ultrasonic time-of-flight for overlapping echoes

In this work, an analysis of the transmission of ultrasonic signals generated by piezoelectric sensors for air applications is presented. Based on this analysis, an ultrasonic response model is obtained for its application to the recognition of objects and structured environments for navigation by autonomous mobile robots. This model enables the analysis of the ultrasonic response that is generated using a pair of sensors in transmitter-receiver configuration using the pulse-echo technique. This is very interesting for recognizing surfaces that simultaneously generate a multiple echo response. This model takes into account the effect of the radiation pattern, the resonant frequency of the sensor, the number of cycles of the excitation pulse, the dynamics of the sensor and the attenuation with distance in the medium. This model has been developed, programmed and verified through a battery of experimental tests. Using this model a new procedure for obtaining accurate time of flight is proposed. This new method is compared with traditional ones, such as threshold or correlation, to highlight its advantages and drawbacks. Finally the advantages of this method are demonstrated for calculating multiple times of flight when the echo is formed by several overlapping echoes.This work has been supported by the Spanish Government projects DPI2006-15313 and DPI2012-36959

Global color estimation of special-effect coatings from measurements by commercially available portable multiangle spectrophotometers

Colors of special-effect coatings have strong dependence on illumination/viewing geometry and an appealing appearance. An open question is to ask about the minimum number of measurement geometries required to completely characterize their observed color shift. A recently published principal components analysis (PCA)-based procedure to estimate the color of special-effect coatings at any geometry from measurements at a reduced set of geometries was tested in this work by using the measurement geometries of commercial portable multiangle spectrophotometers X-Rite MA98, Datacolor FX10, and BYK-mac as reduced sets. The performance of the proposed PCA procedure for the color-shift estimation for these commercial geometries has been examined for 15 special-effect coatings. Our results suggest that for rendering the color appearance of 3D objects covered with special-effect coatings, the color accuracy obtained with this procedure may be sufficient. This is the case especially if geometries of X-Rite MA98 or Datacolor FX10 are used.The authors are grateful to EMRP for funding the project “Multidimensional Reflectometry for Industry.” The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. This study was also supported by the Spanish Ministry of Economy and Competitiveness under grant no. DPI2011-30090-C02-02 and the European Union