The geometrical structure of a tree can consist of thousands, even millions, of branches, twigs and leaves in complex arrangements. The structure contains a lot of useful information and can be used for example to assess a tree's health or calculate parameters such as total wood volume or branch size distribution. Because of the complexity, capturing the structure of an entire tree used to be nearly impossible, but the increased availability and quality of particularly digital cameras and Light Detection and Ranging (LIDAR) instruments is making it increasingly possible. A set of digital images of a tree, or a point cloud of a tree from a LIDAR scan, contains a lot of data, but the information about the tree structure has to be extracted from this data through analysis. This work presents a method of reconstructing 3D models of trees from point clouds. The model is constructed from cylindrical segments which are added one by one. Bayesian inference is used to determine how to optimize the parameters of model segment candidates and whether or not to accept them as part of the model. A Hough transform for finding cylinders in point clouds is presented, and used as a heuristic to guide the proposals of model segment candidates. Previous related works have mainly focused on high density point clouds of sparse trees, whereas the objective of this work was to analyze low resolution point clouds of dense almond trees. The method is evaluated on artificial and real datasets and works rather well on high quality data, but performs poorly on low resolution data with gaps and occlusions.

[pt] O estágio atual das comunicações móveis é caracterizado por um crescimento espetacular da demanda em todos os tipos de ambientes, tanto urbanos densos como suburbanos e rurais . Os planejadores destes sistemas necessitam ferramentas eficientes e economicamente viáveis para a caracterização e projeto deles. O grande objetivo de um bom planejamento é uma boa cobertura, e um dos parâmetros de qualidade é a perda média de propagação. A principal técnica determinística utilizada para o cálculo da perda média de propagação em micro-células em áreas fortemente edificadas é o traçado de raios, a través de um de dois métodos alternativos: o método das imagens e o método de lançamento de raios. Este trabalho apresenta uma formulação detalhada do método de lançamento de raios e dos métodos assintóticos que foram usados afim de calcular os campos eletromagnéticos (direto, refletido e difratado) que permitem calcular a Perda Média de Propagação. Além do mais apresenta-se o método de discriminação espacial usado para acelerar o processo de cálculo. A metodologia proposta foi implementada em programa de computador e são apresentados alguns estudos de caso para ambientes específicos. / [en] The current period of the mobile communications is characterized by a spectacular growth of the demand in all the types of environments, not only in density urbanized cities as suburban and rural. The planners of these systems need efficient and economically viable tools for the design of these systems. The main goal of good planning is a good coverage, and one of the most adopted quality indicators is the path loss of propagation. The mostly used deterministic technique for calculation it in strongly built micro-cells is the tracing of rays, whether the method of the images or the method of launching of rays. This work presents a detailed formularization of the method of launching of rays and of the asymptotic methods which have been used in order to calculate the electromagnetic fields (direct, reflected and diffracted) which allow to calculate the Path Loss of Propagation. Besides it this shown the used method of space discrimination, which was employed to speed up the calculation. The methodology proposal was implemented in computer program and is presented some studies of case for specific environments.

Cette thèse porte sur le développement d'outils et de méthodes pour l'étude des systèmes de localisation Ultra Large Bande en milieu intérieur. Le travail de thèse a été mené pour partie dans le cadre du projet Européen FP7 WHERE2, portant sur la localisation coopérative dans les réseaux cellulaires. La thèse utilise pour sa partie validation des données obtenues dans le cadre de ce projet. La thèse comporte 4 grandes parties. Une première partie présente un outil de raytracing basé sur une description à base de graphes. Afin de pouvoir adresser les problématiques de simulation de la mobilité, l'outil introduit le concept nouveau de signature ainsi qu'un formalisme vectorisé permettant l'accélération du calcul du champ sur les rayons obtenus. Une seconde partie concerne les techniques de localisation utilisées en intérieur et propose une technique originale basée sur des approches ensemblistes. Cette technique est évaluée et comparée à des techniques alternatives comme le des moindres carrés pondérés ou le maximum de vraisemblance. Tirant partie des spécificités de la méthode précédente, une méthode basé sur un test d'hypothèse est décrite. Cette dernière propose d'exploiter les données de puissance reçue (largement disponible en pratique) pour lever les ambiguïtés multimodales dans les cas de carence d'observables précis. Une troisième partie présente 3 aspects de la plateforme dynamique. Tout d'abord un modèle de mobilité réaliste basé sur les «steering behaviors», puis la description sous forme de graphe du réseaux sans fils et enfin un protocole simplifié de communication inter agents. La quatrième partie exploite des données radio obtenues lors d'une campagne de mesure pour valider les différents étages de la plateforme et les algorithmes de localisation proposés. / This thesis focuses on the development of tools and methods dedicated for ultra wide band (UWB) localization systems in indoor environment. The thesis work was conducted within the European FP7 project Where2, about the cooperative localization in cellular networks. Data from a measurement campaign conduct during the project are used to validate the proposed algorithms. This thesis is divided in four parts : The first part is focused on the description of an original raytraing tool based on a graph description. In order to be compliant with the requirement of a mobile simulation, a new concept of rays signature enabling incremental computation, and a vectorized formalism for processing rays are described and implemented. The second part is focused on the indoor localization techniques, where a novel technique based on interval analysis approaches is presented and compared to alternative techniques. Advantageously using this approach, a specific processing based on an hypothesis testing method using received power observations to resolve ambiguities appearing in under determined localization problems is described. A third part describes different aspects of the dynamic platform. In particular a realistic mobility model based on ''steering behaviors'', a graph description of the network scene and an inter agents communication protocol are detailed. The fourth section uses measured data obtained from an heterogeneous measurement campaign to validate both the developed software platform and the proposed localization algorithms.

Subject of this thesis is acceleration of the photon mapping method on a graphic card. The photon mapping is a method for computing almost realistic global illumination of the scene. The computation itself is relatively time-consuming, so the acceleration of it is a hot issue in the field of computer graphics. The photon mapping is described in detail from photon tracing to rendering of the scene. The thesis is then focused on spatial subdivision structures, especially to the uniform grid. The design and the implementation of the application computing the photon mapping on GPU, which is achieved by OpenGL and CUDA interoperability, is described in the next part of the thesis. Lastly, the application is tested properly. The achieved results are reviewed in the conclusion of the thesis.

This thesis deals with the method of distributed ray tracing focusing on optimalization of this method. The method uses simulation of some attributes of light by distributing rays of lights and it produces high quality and partly realistic images. The price for realitic effects is the high computational complexity of the method. The thesis analysis the theory connected with these aspects. A large part describes optimalizations of this method, i.e. searching for the nearest triangle intersection using kd-trees, quasi random sampling with faster convergence, the use of SSE instruction set and fast ray - triangle intersection. These optimalizations brought a noticable speed - up. The thesis includes description of implementation of these techniques. The implementation itself emphasises the practical usability including generating some advanced animations and universal description of objects.

This thesis concentrates on physically based simulation of fluids followed by its photorealistic visualization. It describes one form of Smooth Particle Hydrodynamics methods for viscoelastic fluid simulation and includes its extension for multiple interacting fluids. It also deals with SPH boundary problem and investigates its solution by fixed boundary particles. For visualization of fluids there is a method of Ray Tracing described in detail and it's extended with light absorption in transparent materials. In connection with this method there is also discussed a problem of infinite total reflections and some solution techniques are offered. To extract the surface of the fluid there is used a Marching cubes method and its discussed in terms of Ray Tracing.

This thesis deals with ray tracing methods and their acceleration. It gives partial study and review of algorithms from classical ray shooting algorithm to recursive approach up to distributed ray tracing algorithm. Significant part of this thesis is devoted to BSP tree structure and its subclass of k-D tree, it shows simple algorithm for its construction and traversal. The rest of thesis is dealing with k-D tree construction techniques, which are based on the right choice of the splitting plane inside the every cell of k-D tree. The techniques upon the thesis is based on are space median, object median and relatively new cost model technique named SAH, otherwise as surface area heuristic. All three techniques are put into testing and performance comparison. In the conclusion the results of tests are reviewed, from where SAH is coming out as a winner.

Master thesis is dealing with design and implementation of ray-tracing and path-tracing using IPP library. Theoretical part discusses current trends in acceleration of selected algorithms and also possibilities of parallelization. Design of ray-tracing and path-tracing algorithm and form of parallelization are described in proposal. This part also discusses implementation of adaptive sampling and importance sampling with Monte Carlo method to accelerate path-tracing algorithm. Next part is dealing with particular steps in implementation of selected rendering methods regarding IPP library. Implementation of network interface using Boost library is also discussed. At the end, implemented methods are subjected to performance and quality test. Final product of this thesis is server aplication capable of handling multiple connections which provides visualisation and client application which implements ray-tracing and path-tracing.

The thesis describes theoretical fundamentals of optics and problems of ray-tracing method, ray-triangle intersection computation included. Next section describes concept of three different camera models for ray-tracing method - plain camera, pinehole camea and spherical camera (fish-eye). The thesis comparse properties and capabilities of camera models and their effect to projected image of a scene. The program for raytracing was implemented for purposes of the thesis including implementation of camera models described in the thesis.

VYSOKÉ UČENÍ TECHNICKÉ V BRNĚ Distributed Ray Tracing, also called distribution ray tracing and stochastic ray tracing, is a refinement of ray tracing that allows for the rendering of "soft" phenomena, area light, depth of field and motion blur.