No presente trabalho, utilizou-se o Método da Fronteira Imersa, o qual utiliza dois tipos de malhas computacionais: euleriana (utilizada para o fluido) e lagrangiana (utilizada para representar a interface de separação de dois fluidos). O software livre GMSH foi utilizado para representar um sólido por meio da sua superfície externa e também para gerar uma malha triangular, bidimensional e não estruturada para discretizar essa superfície. Essa superfície foi utilizada como condição inicial para a malha lagrangiana (fronteira imersa). Os dados da malha lagrangiana são armazenados em uma estrutura de dados chamada Halfedge, a qual é largamente utilizada em Computação Gráfica para armazenar superfícies fechadas e orientáveis. Uma vez que a malha lagrangiana esteja armazenada nesta estrutura de dados, passa-se a estudar uma hipotética interação dinâmica entre a fronteira imersa e o escoamento do fluido. Esta interação é estudada apenas em um sentido, considera-se apenas a condição de não deslizamento, isto é, a fronteira imersa acompanhará passivamente um campo de velocidades pré-estabelecido (imposto), sem exercer qualquer força ou influência sobre ele. Foi utilizado um campo de distância local com sinal (função indicadora de fluidos) para identificar o interior e o exterior da superfície que representa a interface entre os fluidos. Este campo de distância é atualizado a cada passo no tempo utilizando idéias de Geometria Computacional, o que tornou o custo computacional para calcular esse campo otimal independente da complexidade geométrica da interface. Esta metodologia mostrou-se robusta e produz uma definição nítida das distintas fases dos fluidos em todos os passos no tempo. Para acompanhar e visualizar de forma mais precisa o comportamento dos fluidos na vizinhança da superfície que representa a interface de separação dos fluido, foi utilizado um algoritmo chamado de Refinamento Adaptativo de Malhas para fazer um refinamento dinâmico da malha euleriana na vizinhança da malha lagrangiana. / The scientific motivation of the present work is the mathematical modeling and the computational simulation of multiphase flows. Specifically, the equations of a two-phase flow are written by combining the Immersed Boundary Method with a suitable fluid indicator function. It is assumed that the fluid equations are discretized on an Eulerian mesh covering completely the flow domain and that the interface between the fluid phases is discretized by a non-structured Lagrangian mesh formed by triangles. In this context, employing tools commonly found in Computational Geometry, the computation of the fluid indicator function is efficiently performed on a block-structured Eulerian mesh bearing dynamical refinement patches. Formed by a set of triangles, the Lagrangian mesh, which is initally generated employing the free software GMSH, is stored in a Halfedge data structure, a data structure which is widely used in Computer Graphics to represent bounded, orientable closed surfaces. Once the Lagrangian mesh has been generated, next, one deals with the hipothetical situation of dealing with the one-way dynamical interaction between the immersed boundary and the fluid flow, that is, considering the non-slip condition, only the action of the flow on the interface is studied. No forces arising on the interface affects the flow, the interface passively being advect with the flow under a prescribed, imposed velocity field. In particular, the Navier-Stokes equations are not solved. The fluid indicator function is given by a signed distance function in a vicinity of the immersed boundary. It is employed to identify interior/exterior points with respect to the bounded, closed region which is assumed to contain one of the fluid phases in its interior. The signed distance is update every time step employing Computational Geometry methods with optimal cost. Several examples in three dimensions, showing the efficiency and efficacy in the computation of the fluid indicator function, are given which employ the dynamical adaptive properties of the Eurlerian mesh for a moving interface.

No presente trabalho, utilizou-se o Método da Fronteira Imersa, o qual utiliza dois tipos de malhas computacionais: euleriana (utilizada para o fluido) e lagrangiana (utilizada para representar a interface de separação de dois fluidos). O software livre GMSH foi utilizado para representar um sólido por meio da sua superfície externa e também para gerar uma malha triangular, bidimensional e não estruturada para discretizar essa superfície. Essa superfície foi utilizada como condição inicial para a malha lagrangiana (fronteira imersa). Os dados da malha lagrangiana são armazenados em uma estrutura de dados chamada Halfedge, a qual é largamente utilizada em Computação Gráfica para armazenar superfícies fechadas e orientáveis. Uma vez que a malha lagrangiana esteja armazenada nesta estrutura de dados, passa-se a estudar uma hipotética interação dinâmica entre a fronteira imersa e o escoamento do fluido. Esta interação é estudada apenas em um sentido, considera-se apenas a condição de não deslizamento, isto é, a fronteira imersa acompanhará passivamente um campo de velocidades pré-estabelecido (imposto), sem exercer qualquer força ou influência sobre ele. Foi utilizado um campo de distância local com sinal (função indicadora de fluidos) para identificar o interior e o exterior da superfície que representa a interface entre os fluidos. Este campo de distância é atualizado a cada passo no tempo utilizando idéias de Geometria Computacional, o que tornou o custo computacional para calcular esse campo otimal independente da complexidade geométrica da interface. Esta metodologia mostrou-se robusta e produz uma definição nítida das distintas fases dos fluidos em todos os passos no tempo. Para acompanhar e visualizar de forma mais precisa o comportamento dos fluidos na vizinhança da superfície que representa a interface de separação dos fluido, foi utilizado um algoritmo chamado de Refinamento Adaptativo de Malhas para fazer um refinamento dinâmico da malha euleriana na vizinhança da malha lagrangiana. / The scientific motivation of the present work is the mathematical modeling and the computational simulation of multiphase flows. Specifically, the equations of a two-phase flow are written by combining the Immersed Boundary Method with a suitable fluid indicator function. It is assumed that the fluid equations are discretized on an Eulerian mesh covering completely the flow domain and that the interface between the fluid phases is discretized by a non-structured Lagrangian mesh formed by triangles. In this context, employing tools commonly found in Computational Geometry, the computation of the fluid indicator function is efficiently performed on a block-structured Eulerian mesh bearing dynamical refinement patches. Formed by a set of triangles, the Lagrangian mesh, which is initally generated employing the free software GMSH, is stored in a Halfedge data structure, a data structure which is widely used in Computer Graphics to represent bounded, orientable closed surfaces. Once the Lagrangian mesh has been generated, next, one deals with the hipothetical situation of dealing with the one-way dynamical interaction between the immersed boundary and the fluid flow, that is, considering the non-slip condition, only the action of the flow on the interface is studied. No forces arising on the interface affects the flow, the interface passively being advect with the flow under a prescribed, imposed velocity field. In particular, the Navier-Stokes equations are not solved. The fluid indicator function is given by a signed distance function in a vicinity of the immersed boundary. It is employed to identify interior/exterior points with respect to the bounded, closed region which is assumed to contain one of the fluid phases in its interior. The signed distance is update every time step employing Computational Geometry methods with optimal cost. Several examples in three dimensions, showing the efficiency and efficacy in the computation of the fluid indicator function, are given which employ the dynamical adaptive properties of the Eurlerian mesh for a moving interface.

The ability of a robot to navigate itself in the environment is a crucial step towards its autonomy. Navigation as a subtask of the development of autonomous robots is the subject of this thesis, focusing on the development of a method for simultaneous localization an mapping (SLAM) of mobile robots in six degrees of freedom (DOF). As a part of this research, a platform for 3D range data acquisition based on a continuously inclined laser rangefinder was developed. This platform is presented, evaluating the measurements and also presenting the robotic equipment on which the platform can be fitted. The localization and mapping task is equal to the registration of multiple 3D images into a common frame of reference. For this purpose, a method based on the Iterative Closest Point (ICP) algorithm was developed. First, the originally implemented SLAM method is presented, focusing on the time-wise performance and the registration quality issues introduced by the implemented algorithms. In order to accelerate and improve the quality of the time-demanding 6DOF image registration, an extended method was developed. The major extension is the introduction of a factorized registration, extracting 2D representations of vertical objects called leveled maps from the 3D point sets, ensuring these representations are 3DOF invariant. The extracted representations are registered in 3DOF using ICP algorithm, allowing pre-alignment of the 3D data for the subsequent robust 6DOF ICP based registration. The extended method is presented, showing all important modifications to the original method. The developed registration method was evaluated using real 3D data acquired in different indoor environments, examining the benefits of the factorization and other extensions as well as the performance of the original ICP based method. The factorization gives promising results compared to a single phase 6DOF registration in vertically structured environments. Also, the disadvantages of the method are discussed, proposing possible solutions. Finally, the future prospects of the research are presented.

Les avancées technologiques dans le domaine informatique (logiciel et matériel) et, en particulier, de la géolocalisation ont permis la démocratisation des modèles numériques. L'arrivée depuis quelques années de véhicules de cartographie mobile a ouvert l'accès à la numérisation 3D mobile terrestre. L'un des avantages de ces nouvelles méthodes d'imagerie de l'environnement urbain est la capacité potentielle de ces systèmes à améliorer les bases de données existantes 2D comme 3D, en particulier leur niveau de détail et la diversité des objets représentés. Les bases de données géographiques sont constituées d'un ensemble de primitives géométriques (généralement des lignes en 2D et des plans ou des triangles en 3D) d'un niveau de détail grossier mais ont l'avantage d'être disponibles sur de vastes zones géographiques. Elles sont issues de la fusion d'informations diverses (anciennes campagnes réalisées manuellement, conception automatisée ou encore hybride) et peuvent donc présenter des erreurs de fabrication. Les systèmes de numérisation mobiles, eux, peuvent acquérir, entre autres, des nuages de points laser. Ces nuages laser garantissent des données d'un niveau de détail très fin pouvant aller jusqu'à plusieurs points au centimètre carré. Acquérir des nuages de points laser présente toutefois des inconvénients :- une quantité de données importante sur de faibles étendues géographiques posant des problèmes de stockage et de traitements pouvant aller jusqu'à plusieurs Téraoctet lors de campagnes d'acquisition importantes- des difficultés d'acquisition inhérentes au fait d'imager l'environnement depuis le sol. Les systèmes de numérisation mobiles présentent eux aussi des limites : en milieu urbain, le signal GPS nécessaire au bon géoréférencement des données peut être perturbé par les multi-trajets voire même stoppé lors de phénomènes de masquage GPS liés à la réduction de la portion de ciel visible pour capter assez de satellites pour en déduire une position spatiale. Améliorer les bases de données existantes grâce aux données acquises par un véhicule de numérisation mobile nécessite une mise en cohérence des deux ensembles. L'objectif principal de ce manuscrit est donc de mettre en place une chaîne de traitements automatique permettant de recaler bases de données géographiques et nuages de points laser terrestre (provenant de véhicules de cartographies mobiles) de la manière la plus fiable possible. Le recalage peut se réaliser de manière différentes. Dans ce manuscrit, nous avons développé une méthode permettant de recaler des nuages laser sur des bases de données, notamment, par la définition d'un modèle de dérive particulièrement adapté aux dérives non-linéaires de ces données mobiles. Nous avons également développé une méthode capable d'utiliser de l'information sémantique pour recaler des bases de données sur des nuages laser mobiles. Les différentes optimisations effectuées sur notre approche nous permettent de recaler des données rapidement pour une approche post-traitements, ce qui permet d'ouvrir l'approche à la gestion de grands volumes de données (milliards de points laser et milliers de primitives géométriques).Le problème du recalage conjoint a été abordé. Notre chaîne de traitements a été testée sur des données simulées et des données réelles provenant de différentes missions effectuées par l'IGN / Technological advances in computer science (software and hardware) and particularly, GPS localization made digital models accessible to all people. In recent years, mobile mapping systems has enabled large scale mobile 3D scanning. One advantage of this technology for the urban environment is the potential ability to improve existing 2D or 3D database, especially their level of detail and variety of represented objects. Geographic database consist of a set of geometric primitives (generally 2D lines and plans or triangles in 3D) with a coarse level of detail but with the advantage of being available over wide geographical areas. They come from the fusion of various information (old campaigns performed manually, automated or hybrid design) wich may lead to manufacturing errors. The mobile mapping systems can acquire laser point clouds. These point clouds guarantee a fine level of detail up to more than one points per square centimeter. But there are some disavantages :- a large amount of data on small geographic areas that may cause problems for storage and treatment of up to several Terabyte during major acquisition,- the inherent acquisition difficulties to image the environment from the ground. In urban areas, the GPS signal required for proper georeferencing data can be disturbed by multipath or even stopped when GPS masking phenomena related to the reduction of the portion of the visible sky to capture enough satellites to find a good localization. Improve existing databases through these dataset acquired by a mobile mapping system requires alignment of these two sets. The main objective of this manuscript is to establish a pipeline of automatic processes to register these datasets together in the most reliable manner. Co-registration this data can be done in different ways. In this manuscript we have focused our work on the registration of mobile laser point cloud on geographical database by using a drift model suitable for the non rigid drift of these kind of mobile data. We have also developped a method to register geographical database containing semantics on mobile point cloud. The different optimization step performed on our methods allows to register the data fast enough for post-processing pipeline, which allows the management of large volumes of data (billions of laser points and thousands geometric primitives). We have also discussed on the problem of joint deformation. Our methods have been tested on simulated data and real data from different mission performed by IGN

Os fundamentos teóricos desenvolvidos neste trabalho e que dão suporte aos métodos propostos garantem que as estimativas obtidas sejam sempre conservadoras (no sentido de que elas são sempre subconjuntos da região de estabilidade verdadeira) e, portanto, possuam elevado grau de confiança ao concluir sobre a estabilidade do sistema. Os métodos apresentados consistem em extensões dos métodos Closest UEP e CUEP, utilizados na análise de estabilidade transitória de sistemas elétricos de potência, para sistemas que admitem FEG. Embora os métodos Closest UEP e CUEP forneçam estimativas de forma rápida e precisa, sua aplicação está limitada à existência de uma Função Energia (FE) para o sistema, o que consiste em uma forte limitação. Muitos sistemas não admitem FE e, mesmo quando se pode provar a existência de uma FE, a impossibilidade de exibi-la impede a aplicação dos métodos citados. Outra contribuição deste trabalho consiste em um método computacional que permite a obtenção de uma FEG para sistemas polinomiais. O método apresentado também é aplicado a uma classe de problemas não polinomiais, provenientes da modelagem de sistemas elétricos de potência, mediante uma mudança não linear de variáveis que permite a construção de um sistema polinomial equivalente. Através dos métodos apresentados, visa-se disponibilizar métodos computacionais que permitam a obtenção de estimativas rápidas e precisas e que possam ser aplicados a uma ampla classe de sistemas: aqueles que admitem FEG. Com isso, almeja-se não somente contribuir para o desenvolvimento de métodos para análise de estabilidade de sistemas elétricos de potência mas, também, disponibilizá-los a outras áreas do conhecimento. / In this work, we develop computational methods to estimate stability regions and the relevant part of stability boundary of attracting sets of nonlinear dynamical systems. Such methods are based on Generalized Energy Function (GEF) theory and, therefore, can be applied to a larger class of problems than those based on Energy Functions (EF). The theoretical foundations developed in this work, which support the proposed methods, ensure that the estimates are always conservative (in the sense that they are subsets of the true stability region), providing high confidence level when asserting the stability of a system. The presented methods are extensions of the Closest UEP and the CUEP methods, used in the assessment of stability of electrical power systems, to the systems that admit GEF. Even though the Closest UEP and CUEP methods provide estimates in a fast and accurate way, they are only applicable to systems that admit EFs, which consists in a strong limitation for their usage. Many systems do not admit EF and, even if it is possible to prove the existence of an EF, the impossibility to exhibit it in the form of elementary mathematical functions prevents the application of such methods. Other contribution of this work is a computational method to obtain a GEF for polinomial systems. We also applied the presented method to a class of non polinomial systems arising from electrical power system models, after a nonlinear change of variables that provides an equivalent polinomial system. By means of the proposed methods, we aim to offer computational methods to allow fast and accurate stability region estimates which could be used in a broad class of dynamical systems: those that admit GEF. This way, we plan to contribute for the development of methods used in the assessment of stability of electrical power systems and make such tools available to systems from other areas of science.

Os fundamentos teóricos desenvolvidos neste trabalho e que dão suporte aos métodos propostos garantem que as estimativas obtidas sejam sempre conservadoras (no sentido de que elas são sempre subconjuntos da região de estabilidade verdadeira) e, portanto, possuam elevado grau de confiança ao concluir sobre a estabilidade do sistema. Os métodos apresentados consistem em extensões dos métodos Closest UEP e CUEP, utilizados na análise de estabilidade transitória de sistemas elétricos de potência, para sistemas que admitem FEG. Embora os métodos Closest UEP e CUEP forneçam estimativas de forma rápida e precisa, sua aplicação está limitada à existência de uma Função Energia (FE) para o sistema, o que consiste em uma forte limitação. Muitos sistemas não admitem FE e, mesmo quando se pode provar a existência de uma FE, a impossibilidade de exibi-la impede a aplicação dos métodos citados. Outra contribuição deste trabalho consiste em um método computacional que permite a obtenção de uma FEG para sistemas polinomiais. O método apresentado também é aplicado a uma classe de problemas não polinomiais, provenientes da modelagem de sistemas elétricos de potência, mediante uma mudança não linear de variáveis que permite a construção de um sistema polinomial equivalente. Através dos métodos apresentados, visa-se disponibilizar métodos computacionais que permitam a obtenção de estimativas rápidas e precisas e que possam ser aplicados a uma ampla classe de sistemas: aqueles que admitem FEG. Com isso, almeja-se não somente contribuir para o desenvolvimento de métodos para análise de estabilidade de sistemas elétricos de potência mas, também, disponibilizá-los a outras áreas do conhecimento. / In this work, we develop computational methods to estimate stability regions and the relevant part of stability boundary of attracting sets of nonlinear dynamical systems. Such methods are based on Generalized Energy Function (GEF) theory and, therefore, can be applied to a larger class of problems than those based on Energy Functions (EF). The theoretical foundations developed in this work, which support the proposed methods, ensure that the estimates are always conservative (in the sense that they are subsets of the true stability region), providing high confidence level when asserting the stability of a system. The presented methods are extensions of the Closest UEP and the CUEP methods, used in the assessment of stability of electrical power systems, to the systems that admit GEF. Even though the Closest UEP and CUEP methods provide estimates in a fast and accurate way, they are only applicable to systems that admit EFs, which consists in a strong limitation for their usage. Many systems do not admit EF and, even if it is possible to prove the existence of an EF, the impossibility to exhibit it in the form of elementary mathematical functions prevents the application of such methods. Other contribution of this work is a computational method to obtain a GEF for polinomial systems. We also applied the presented method to a class of non polinomial systems arising from electrical power system models, after a nonlinear change of variables that provides an equivalent polinomial system. By means of the proposed methods, we aim to offer computational methods to allow fast and accurate stability region estimates which could be used in a broad class of dynamical systems: those that admit GEF. This way, we plan to contribute for the development of methods used in the assessment of stability of electrical power systems and make such tools available to systems from other areas of science.

The nearest neighbour problem is of practical significance in a number of fields. Often we are interested in finding an object near to a given query object. The problem is old, and a large number of solutions have been proposed for it in the literature. However, it remains the case that even the most popular of the techniques proposed for its solution have not been compared against each other. Also, many techniques, including the old and popular ones, can be implemented in a number of ways, and often the different implementations of a technique have not been thoroughly compared either. This research presents a detailed investigation of different implementations of two popular nearest neighbour search data structures, KDTrees and Metric Trees, and compares the different implementations of each of the two structures against each other. The best implementations of these structures are then compared against each other and against two other techniques, Annulus Method and Cover Trees. Annulus Method is an old technique that was rediscovered during the research for this thesis. Cover Trees are one of the most novel and promising data structures for nearest neighbour search that have been proposed in the literature.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-06-07T15:41:47Z No. of bitstreams: 1 lucianowalentyxaviercejnog.pdf: 14234810 bytes, checksum: 492ebb7393b5f0e7cfc6e822067fe492 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-06-24T13:12:44Z (GMT) No. of bitstreams: 1 lucianowalentyxaviercejnog.pdf: 14234810 bytes, checksum: 492ebb7393b5f0e7cfc6e822067fe492 (MD5) / Made available in DSpace on 2017-06-24T13:12:44Z (GMT). No. of bitstreams: 1 lucianowalentyxaviercejnog.pdf: 14234810 bytes, checksum: 492ebb7393b5f0e7cfc6e822067fe492 (MD5) Previous issue date: 2015-09-21 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho visa melhorar um método clássico para o problema de registro rígido, o ICP (iterative Closest Point), fazendo com que a busca dos pontos mais próximos, uma de suas fases principais, considere informações aproximadas da geometria local de cada ponto combinadas à distância Euclidiana originalmente usada. Para isso é necessária uma etapa de pré-processamento, na qual a geometria local é estimada em tensores de orientação de segunda ordem. É definido o CTSF, um fator de similaridade entre tensores. O ICP é alterado de modo a considerar uma combinação linear do CTSF com a distância Euclidiana para estabelecer correspondências entre duas nuvens de pontos, variando os pesos relativos entre os dois fatores. Isso proporciona uma capacidade maior de convergência para ângulos maiores em relação ao ICP original, tornando o método comparável aos que constituem o estado da arte da área. Para comprovar o ganho obtido, foram realizados testes exaustivos em malhas com características geométricas variadas, para diferentes níveis de ruído aditivo, outliers e em casos de sobreposição parcial, variando os parâmetros do método de estimativa dos tensores. Foi definida uma nova base com malhas sintéticas para os experimentos, bem como um protocolo estatístico de avaliação quantitativa. Nos resultados, a avaliação foi feita de modo a determinar bons valores de parâmetros para malhas com diferentes características, e de que modo os parâmetros afetam a qualidade do método em situações com ruído aditivo, outliers, e sobreposição parcial. / This work aims to enhance a classic method for the rigid registration problem, the ICP (Iterative Closest Point), modifying one of its main steps, the closest point search, in order to consider approximated information of local geometry combined to the Euclidean distance, originally used. For this, a preprocessing stage is applied, in which the local geometry is estimated in second-order orientation tensors. We define the CTSF, a similarity factor between tensors. Our method uses a linear combination between this factor and the Euclidean distance, in order to establish correspondences, and a strategy of weight variation between both factors. This increases the convergence probability for higher angles with respect to the original ICP, making our method comparable to some of the state-of-art techniques. In order to comprove the enhancement, exhaustive tests were made in point clouds with different geometric features, with variable levels of additive noise and outliers and in partial overlapping situations, varying also the parameters of the tensor estimative method. A dataset of synthetic point clouds was defined for the experiments, as well as a statistic protocol for quantitative evaluation. The results were analyzed in order to highlight good parameter ranges for different point clouds, and how these parameters affect the behavior of the method in situations of additive noise, outliers and partial overlapping.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-06-07T17:49:03Z No. of bitstreams: 1 fernandoakiodearaujoyamada.pdf: 21095203 bytes, checksum: 1842e801a538bdeef0368c963b9d98b7 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-06-24T13:47:22Z (GMT) No. of bitstreams: 1 fernandoakiodearaujoyamada.pdf: 21095203 bytes, checksum: 1842e801a538bdeef0368c963b9d98b7 (MD5) / Made available in DSpace on 2017-06-24T13:47:22Z (GMT). No. of bitstreams: 1 fernandoakiodearaujoyamada.pdf: 21095203 bytes, checksum: 1842e801a538bdeef0368c963b9d98b7 (MD5) Previous issue date: 2016-03-15 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / No problema de registro rígido por pares é preciso encontrar uma transformação rígida que alinha duas nuvens de pontos. A sulução clássica e mais comum é o algoritmo Iterative Closest Point (ICP). No entanto, o ICP e muitas de suas variantes requerem que as nuvens de pontos já estejam grosseiramente alinhadas. Este trabalho apresenta um método denominado Shape-based Weighting Covariance Iterative Closest Point (SWC-ICP), uma melhoria do ICP clássico. A abordagem proposta aumenta a possibilidade de alinhar corretamente duas nuvens de pontos, independente da pose inicial, mesmo quando existe apenas sobreposição parcial entre elas, ou na presença de ruído e outliers. Ela se beneficia da geometria local dos pontos, codificada em tensores de orientação de segunda ordem, para prover um segundo conjunto de correspondências para o ICP. A matriz de covariância cruzada computada a partir deste conjunto é combinada com a matriz de covariância cruzada usual, seguindo uma estratégia heurística. Para comparar o método proposto com algumas abordagens recentes, um protocolo de avaliação detalhado para registro rígido é apresentado. Os resultados mostram que o SWC-ICP está entre os melhores métodos comparados, com performance superior em situações de grande deslocamento angular, mesmo na presença de ruído e outliers. / In the pairwise rigid registration problem we need to find a rigid transformation that aligns two point clouds. The classical and most common solution is the Iterative Closest Point (ICP) algorithm. However, the ICP and many of its variants require that the point clouds are already coarsely aligned. We present in this work a method named Shape-based Weighting Covariance Iterative Closest Point (SWC-ICP), an improvement over the classical ICP. Our approach improves the possibility to correctly align two point clouds, regardless of the initial pose, even when there is only a partial overlapping between them, or in the presence of noise and outliers. It benefits from the local geometry of the points, encoded in second-order orientation tensors, to provide a second correspondences set to the ICP. The cross-covariance matrix computed from this set is combined with the usual cross-covariance matrix following a heuristic strategy. In order to compare our method with some recent approaches, we present a detailed evaluation protocol to rigid registration. Results show that the SWC-ICP is among the best methods compared, with superior performance in situations of wide angular displacement, even in situations of noise and outliers.

The Iterative Closest Point (ICP) algorithm has been an extremely popular method for 3D points or surface registration. Given two point sets, it simultaneously solves for correspondences and estimates the motion between these two point sets. However, by only registering two such views at a time, ICP fails to exploit the redundant information available in multiple views that have overlapping regions. In this thesis, a multiview extension of the ICP algorithm is provided that simultaneously averages the redundant information available in the views with overlapping regions. Variants of this method that carry out such simultaneous registration in a causal manner and that utilize the transitivity property of point correspondences are also provided. The improved accuracy in registration of these motion averaged approaches in comparison with the conventional ICP method is established through extensive experiments. In addition, the motion averaged approaches are compared with the existing multiview techniques of Bergevin et. al. and Benjemaa et. al. The results of the methods applied to the Happy Buddha and the Stanford Bunny datasets of 3D Stanford repository and to the Pooh and the Bunny datasets of the Ohio (MSU/WSU) Range Image database are also presented.