Estudi i implementació d’un mètode de reconstrucció 3D basat en SfM i registre de vistes 3D parcials

Aquest projecte es basarà en reconstruir una imatge 3D gran a partir d’una seqüència d’imatges 2D capturades per una càmera. Ens centrem en l’estudi de les bases matemàtiques de la visió per computador així com en diferents mètodes emprats en la reconstrucció 3D d’imatges. Per portar a terme aquest estudi s’utilitza la plataforma de desenvolupament MatLab ja que permet tractar operacions matemàtiques, imatges i matrius de gran tamany amb molta senzillesa, rapidesa i eficiència, per aquesta raó s’usa en moltes recerques sobre aquest tema. El projecte aprofundeix en el tema descrit anteriorment estudiant i implementant un mètode que consisteix en aplicar Structure From Motion (SFM) a pocs frames seguits obtinguts d’una seqüència d’imatges 2D per crear una reconstrucció 3D. Quan s’han creat dues reconstruccions 3D consecutives i fent servir un frame com a mínim en comú entre elles, s’aplica un mètode de registre d’estructures 3D, l’Iterative Closest Point (ICP), per crear una reconstrucció 3D més gran a través d’unir les diferents reconstruccions obtingudes a partir de SfM. El mètode consisteix en anar repetint aquestes operacions fins al final dels frames per poder aconseguir una reconstrucció 3D més gran que les petites imatges que s’aconsegueixen a través de SfM. A la Figura 1 es pot veure un esquema del procés que es segueix. Per avaluar el comportament del mètode, utilitzem un conjunt de seqüències sintètiques i un conjunt de seqüències reals obtingudes a partir d’una càmera. L’objectiu final d’aquest projecte és construir una nova toolbox de MatLab amb tots els mètodes per crear reconstruccions 3D grans per tal que sigui possible tractar amb facilitat aquest problema i seguir-lo desenvolupant en un futur

Slow dynamis in the 3D gonihedric model

We provide analytical evidence of stochastic resonance in polarization switching vertical-cavity surface-emitting lasers (VCSELs). We describe the VCSEL by a two-mode stochastic rate equation model and apply a multiple time-scale analysis. We were able to reduce the dynamical description to a single stochastic differential equation, which is the starting point of the analytical study of stochastic resonance. We confront our results with numerical simulations on the original rate equations, validating the use of a multiple time-scale analysis on stochastic equations as an analytical tool.

Characterisation of the LMS200 laser beam under the influence of blockage surfaces. Influence on 3D scanning of tree orchards

The geometric characterisation of tree orchards is a high-precision activity comprising the accurate measurement and knowledge of the geometry and structure of the trees. Different types of sensors can be used to perform this characterisation. In this work a terrestrial LIDAR sensor (SICK LMS200) whose emission source was a 905-nm pulsed laser diode was used. Given the known dimensions of the laser beam cross-section (with diameters ranging from 12 mm at the point of emission to 47.2 mm at a distance of 8 m), and the known dimensions of the elements that make up the crops under study (flowers, leaves, fruits, branches, trunks), it was anticipated that, for much of the time, the laser beam would only partially hit a foreground target/object, with the consequent problem of mixed pixels or edge effects. Understanding what happens in such situations was the principal objective of this work. With this in mind, a series of tests were set up to determine the geometry of the emitted beam and to determine the response of the sensor to different beam blockage scenarios. The main conclusions that were drawn from the results obtained were: (i) in a partial beam blockage scenario, the distance value given by the sensor depends more on the blocked radiant power than on the blocked surface area; (ii) there is an area that influences the measurements obtained that is dependent on the percentage of blockage and which ranges from 1.5 to 2.5 m with respect to the foreground target/object. If the laser beam impacts on a second target/object located within this range, this will affect the measurement given by the sensor. To interpret the information obtained from the point clouds provided by the LIDAR sensors, such as the volume occupied and the enclosing area, it is necessary to know the resolution and the process for obtaining this mesh of points and also to be aware of the problem associated with mixed pixels.

Innovative LIDAR 3D dynamic measurement system to estimate fruit-tree leaf area

In this work, a LIDAR-based 3D Dynamic Measurement System is presented and evaluated for the geometric characterization of tree crops. Using this measurement system, trees were scanned from two opposing sides to obtain two three-dimensional point clouds. After registration of the point clouds, a simple and easily obtainable parameter is the number of impacts received by the scanned vegetation. The work in this study is based on the hypothesis of the existence of a linear relationship between the number of impacts of the LIDAR sensor laser beam on the vegetation and the tree leaf area. Tests performed under laboratory conditions using an ornamental tree and, subsequently, in a pear tree orchard demonstrate the correct operation of the measurement system presented in this paper. The results from both the laboratory and field tests confirm the initial hypothesis and the 3D Dynamic Measurement System is validated in field operation. This opens the door to new lines of research centred on the geometric characterization of tree crops in the field of agriculture and, more specifically, in precision fruit growing.

Splat-based surface reconstruction from defect-laden point sets

We introduce a method for surface reconstruction from point sets that is able to cope with noise and outliers. First, a splat-based representation is computed from the point set. A robust local 3D RANSAC-based procedure is used to filter the point set for outliers, then a local jet surface - a low-degree surface approximation - is fitted to the inliers. Second, we extract the reconstructed surface in the form of a surface triangle mesh through Delaunay refinement. The Delaunay refinement meshing approach requires computing intersections between line segment queries and the surface to be meshed. In the present case, intersection queries are solved from the set of splats through a 1D RANSAC procedure

Testing of stair climbing point-of-choice prompts in Barcelona at an outdoor set of stairs and scalators on the Montjuïc site

Regular stair climbing has well-documented health dividends, such as increased fitness and strength, weight loss and reduced body fat, improved lipid profiles and reduced risk of osteoporosis. The general absence of barriers to participation makes stair climbing an ideal physical activity (PA) for health promotion. Studies in the US and the UK have consistently shown that interventions to increase the accumulation of lifestyle PA by climbing stairs rather than using the escalators are effective. However, there are no previous in Catalonia. This project tested one message for their ability to prompt travelers on the Montjuïc site to choose the stairs rather than the escalator when climbing up the Monjuïc hill. One standard message, " Take the stairs! 7 minutes of stair climbing a day protects your heart" provided a comparison with previous research done in the UK. Translated into Catalan and Spanish, it was presented on a poster positioned at the point of choice between the stairs and the escalator. The study used a quasi-experimental, interrupted time series design. Travelers, during several and specific hours on two days of the week, were coded for stair or escalator use, gender, age, ethnic status, presence of accompanying children or bags by one observer. Overall, the intervention resulted in a 81% increase in stair climbing. In the follow-up period without messages, stair climbing dropped out to baseline levels. This preliminary study showed a significant effect on stair use. However, caution is needed since results are based on a small sample and, only a low percentage of the sample took the stairs at baseline or the intervention phase . Future research on stair use in Catalonia should focus on using bigger samples, different sites (metro stations, airports, shopping centers, etc) , different messages and techniques to promote stair climbing.

Terrestrial laser scanning for landslides deformation monitoring

Within last few years a new type of instruments called Terrestrial Laser Scanners (TLS) entered to the commercial market. These devices brought a possibility to obtain completely new type of spatial, three dimensional data describing the object of interest. TLS instruments are generating a type of data that needs a special treatment. Appearance of this technique made possible to monitor deformations of very large objects, like investigated here landslides, with new quality level. This change is visible especially with relation to the size and number of the details that can be observed with this new method. Taking into account this context presented here work is oriented on recognition and characterization of raw data received from the TLS instruments as well as processing phases, tools and techniques to do them. Main objective are definition and recognition of the problems related with usage of the TLS data, characterization of the quality single point generated by TLS, description and investigation of the TLS processing approach for landslides deformation measurements allowing to obtain 3D deformation characteristic and finally validation of the obtained results. The above objectives are based on the bibliography studies and research work followed by several experiments that will prove the conclusions.

Prototipus de visualització d’informació vitivinícola en 3D

iii. El projecte final a consistit en la creació prototipus de SIG (Sistema d’informació Geogràfica) per l’empresa T-Systems. El sistema desenvolupat es troba format per un conjunt de serveis web 3D utilitzant ArcGIS Server 9.2, amb la informació de les parcel•les vitivinícoles del Priorat (Catalunya), i un client personalitzat a les necessitats de l’usuari final, utilitzant ArcGIS Explorer 410. Per programar les eines personalitzades s’ha utilitzat Visual Studio 2005 (Visual Basic .NET).

Proper actions, fixed-point algebras and naturality in nonabelian duality

"Vegeu el resum a l'incici del document del fitxer adjunt."

Art en tres dimensions: construcció de renders 3D amb renders 3D studio max

Treball de recerca realitzat per un alumne d’ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit científic del Jovent l’any 2008. Existeixen diversos programes informàtics per a la generació d’imatges en format 3D. S’analitza breument l’oferta del mercat actual de la tecnologia de programari més emprada en la producció de gràfics 3D amb ordinador, identificant les vessants positives i negatives de cadascun. Posteriorment s’examina en profunditat el programa 3D Studio Max, per tal de conèixer-ne les eines de creació d’escenes virtuals i les seves funcionalitats. Finalment s’han desenvolupat projectes d’escenaris 3D en els quals es puguin aplicar els coneixements tècnics obtinguts en la recerca, sempre conceptualitzant aquestes propostes amb un cert criteri artístic.

Two different 3D biogeochemical models for the NW mediterranean sea: validation with Meris data and intercomparison

Report for the scientific sojourn carried out at the University of New South Wales from February to June the 2007. Two different biogeochemical models are coupled to a three dimensional configuration of the Princeton Ocean Model (POM) for the Northwestern Mediterranean Sea (Ahumada and Cruzado, 2007). The first biogeochemical model (BLANES) is the three-dimensional version of the model described by Bahamon and Cruzado (2003) and computes the nitrogen fluxes through six compartments using semi-empirical descriptions of biological processes. The second biogeochemical model (BIOMEC) is the biomechanical NPZD model described in Baird et al. (2004), which uses a combination of physiological and physical descriptions to quantify the rates of planktonic interactions. Physical descriptions include, for example, the diffusion of nutrients to phytoplankton cells and the encounter rate of predators and prey. The link between physical and biogeochemical processes in both models is expressed by the advection-diffusion of the non-conservative tracers. The similarities in the mathematical formulation of the biogeochemical processes in the two models are exploited to determine the parameter set for the biomechanical model that best fits the parameter set used in the first model. Three years of integration have been carried out for each model to reach the so called perpetual year run for biogeochemical conditions. Outputs from both models are averaged monthly and then compared to remote sensing images obtained from sensor MERIS for chlorophyll.

Point-occurrence self-similarity in crackling-noise systems and in other complex systems

It has been recently found that a number of systems displaying crackling noise also show a remarkable behavior regarding the temporal occurrence of successive events versus their size: a scaling law for the probability distributions of waiting times as a function of a minimum size is fulfilled, signaling the existence on those systems of self-similarity in time-size. This property is also present in some non-crackling systems. Here, the uncommon character of the scaling law is illustrated with simple marked renewal processes, built by definition with no correlations. Whereas processes with a finite mean waiting time do not fulfill a scaling law in general and tend towards a Poisson process in the limit of very high sizes, processes without a finite mean tend to another class of distributions, characterized by double power-law waiting-time densities. This is somehow reminiscent of the generalized central limit theorem. A model with short-range correlations is not able to escape from the attraction of those limit distributions. A discussion on open problems in the modeling of these properties is provided.

Pessebre virtual: disseny i exportació

Aquest projecte és una part d’un projecte més ampli consistent en estudiar un format gràfic que permeti exportar una escena modelada en Blender i importar aquesta mateixa escena en un entorn interactiu basat en Visual C++ amb OpenGL. D’aquesta forma, disposem de la capacitat de modelat de Blender i de la interacció i visualització de la llibreria OpenGL. Aquest format ha de representar geometria i textures imprescindiblement, i si és possible, d’altres factors importants com il·luminació, visualització i moviment. La part del projecte explicada en aquesta memòria consisteix en estudiar el format gràfic més adient per representar els diferents factors de realisme de l’escena (geometria, textura, etc.) havent triat el format OBJ per la seva capacitat de representació i fàcil edició. Per a provar el format, s’ha dissenyat un diorama de pessebre utilitzant les capacitats de modelatge de Blender. Pel que respecta les figures, aspecte important per a considerar l’escena com a pessebre, s’ha utilitzat un escàner 3D que ha obtingut representacions de malla 3D, a partir de figures reals de pessebre, que posteriorment han estat texturades. S’ha generat un vídeo del diorama de pessebre que permet veure’n tots els detalls navegant amb el punt de vista per l’escena. Aquest vídeo s’ha exposat en la mostra de pessebres de la Associació Pessebrista de Sabadell el Nadal del 2008.

Desenvolupament d'un videojoc en 3D

La industria de los videojuegos crece exponencialmente y está ya superando a otras industrias punteras del ocio. En este proyecto, nos hemos planteado la realización de un videojuego con visualización en el espacio real 3D. Para la realización del videojuego se ha usado el siguiente software: Blender para diseñar los modelos 3D, C++ como lenguaje de programación para desarrollar el código y un conjunto de librerías básicas para desarrollar un videojuego llamadas Ogre3d (Motor Gráfico). La lógica del movimiento 3D y los choques entre las partículas del juego ha sido diseñada enteramente en este proyecto acorde con las necesidades del videojuego, y de forma compatible a los ficheros de Blender y a las librerías OGRE3D.

Juguem amb la Wii!: telemesura d'acceleracions en 3D : desenvolupament d'un projecte informàtic de codi lliure

Treball de recerca realitzat per un alumne d'ensenyament secundari i guardonat amb un Premi CIRIT per fomentar l'esperit científic del Jovent l'any 2009. Aquest treball de recerca és un projecte sobre el disseny i la creació d’un programa informàtic de codi obert amb l’objectiu de mesurar acceleracions en tres dimensions utilitzant el comandament de la wii, també conegut com a wiimote. Per tant, s'ha creat un programa que es connecta amb el wiimote, en rep les dades, les guarda i les representa per analitzar posteriorment diversos tipus de moviments i les seves acceleracions. Per tal de fer això es va aprofitar una biblioteca de funcions de codi obert ja existent que aporta les funcions principals per a la comunicació i control del comandament. El codi obert és un concepte que s’utilitza per als projectes informàtics, el codi dels quals està a la disposició de qui el necessiti. La biblioteca utilitzada està escrita en llenguatge C i per a plataforma Linux, i per tal d’aprofitar-la es va haver d’aprendre a utilitzar tant el llenguatge com la plataforma ja que no s'hi havia treballat mai abans. Gràcies a aquest projecte s'ha tingut la possibilitat de veure el funcionament d’algunes tecnologies alternatives i veure’n els avantatges sobre les convencionals o propietàries. Així doncs, des del punt de vista de l'autor, ha estat útil i enriquidor el fet de realitzar-lo.