El modelat d'escenes és clau en un gran ventall d'aplicacions que van des de la generació mapes fins a la realitat augmentada. Aquesta tesis presenta una solució completa per a la creació de models 3D amb textura. En primer lloc es presenta un mètode de Structure from Motion seqüencial, a on el model 3D de l'entorn s'actualitza a mesura que s'adquireix nova informació visual. La proposta és més precisa i robusta que l'estat de l'art. També s'ha desenvolupat un mètode online, basat en visual bag-of-words, per a la detecció eficient de llaços. Essent una tècnica completament seqüencial i automàtica, permet la reducció de deriva, millorant la navegació i construcció de mapes. Per tal de construir mapes en àrees extenses, es proposa un algorisme de simplificació de models 3D, orientat a aplicacions online. L'eficiència de les propostes s'ha comparat amb altres mètodes utilitzant diversos conjunts de dades submarines i terrestres. / Scene modeling has a key role in applications ranging from visual mapping to augmented reality. This thesis presents an end-to-end solution for creating accurate, automatic 3D textured models, with contributions at different levels. First, we discuss a method developed within the framework of sequential Structure from Motion, where a 3D model of the environment is maintained and updated as visual information becomes available. The technique is more accurate and robust than state-of-the-art 3D modeling approaches. We also develop an online effcient loop-closure detection algorithm, allowing the reduction of drift and uncertainties for mapping and navigation. Inspired from visual bag-of-words, the technique is entirely sequential and automatic. Lastly, motivated by the need to map large areas, we propose a 3D model simplification oriented towards online applications. We discuss the efficiency of the proposals and compare them with state-of-the-art approaches, using a series of challenging datasets both in underwater and outdoor scenarios.

Thesis (M.F.A.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaf 50).

Thesis (M.App.Sc.) - Carleton University, / Includes bibliographical references (p. 82-88). Also available in electronic format on the Internet.

Thesis (M.S.)--Florida State University, 2006. / Advisor: Piyush Kumar, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains viii, 45 pages. Includes bibliographical references.

O movimento relativo entre superfícies planas de contato são comuns a muitos projetos de engenharia. Na operação de muitos mecanismos identificam-se os problemas de atrito como um dos principais obstáculos para o êxito do funcionamento desses dispositivos. Neste trabalho avaliou-se a influência da pressão nominal de contato no atrito estático entre superfícies de aço ABNT 1020 e 1045 contra uma placa de vidro. As superfícies dos corpos de prova foram obtidas através do Processo de Fabricação por Usinagem Com Ferramenta de Geometria Não Definida – Retificação Plana Tangencial. Os corpos de prova foram constituídos de dois grupos: o Grupo A (tipo copo - ABNT1010) e do Grupo B (tipo Maciço - ABNT1045). Todas as superfícies foram caracterizadas quanto à rugosidade, utilizando-se um perfilômetro 3-D óptico sem contato. Para as medições do atrito estático foi utilizado um sistema plano inclinado, com automatização para detecção dos movimentos dos corpos de prova ao longo do tempo. Demonstrou-se que a pressão nominal não influencia os valores de coeficiente de atrito estático. Investigou-se a partir de então, um possível efeito da rugosidade no atrito. A partir dos parâmetros de rugosidade 3D foram calculados os momentos espectrais m0, m2 e m4, e o Parâmetro Largura de Banda, Alfa (α) que foi correlacionado com o coeficiente de atrito estático. Dentro dos parâmetros analisados: Sq, Sdq e Sds, o parâmetro Sq foi o que apresentou a maior discrepância entre os dados coletados. Com base na análise estatística de variância com nível de confiança de 5%, do parâmetro Sq, as amostras foram realocadas em 4 grupos para os quais foram calculados os Parâmetros Alfa. Considerando-se estes grupos de amostras, mostrou-se que o parâmetro alfa afetou o coeficiente de atrito estático, ou seja, quanto maior o parâmetro, maior o coeficiente de atrito estático. / The relative movement among flat surfaces in contact is common for many engineering projects. During the operation of many mechanisms, friction problems are identified as a main obstacle to the successful performance of them. In this study the influence of nominal pressure contact on static friction between steel surfaces (ABNT 1020 and 1045) and glass plate is evaluated. The specimens‘ surfaces were obtained by means of a manufacturing process classified as machining with undefined tool – tangential plane grinding. The specimens were constituted by two groups: the group A (type cup – ABNT1010) and the group B (type compact – ABNT1045). All specimens were characterized with respect to surface roughness, using a 3-D optical non-contact profilometer. For static friction measurements, an inclined plan system was used, with an automated detection of movements of specimens along time. The nominal contact pressure not has any effect on the values of static friction coefficient. Since then, a possible effect of surface roughness on friction was investigated. The spectral moments m0, m2 and m4, and the bandwidth parameter, Alpha (α), were calculated from the 3-D roughness parameters, and this latter was correlated with static friction coefficient. Within the analyzed parameters: Sq, Sdq and Sds, the Sq parameter presented the largest discrepancy within the sampling data. Based on the statistical analysis of variance, with a confidence level of 5%, of Sq parameter, the specimens were relocated into 4 groups, for which we calculated alpha parameter. Considering these groups, we demonstrated that the alpha parameter affected the static friction coefficient, that is, the higher this parameter, the greater the static friction coefficient.

Orientadores: Inacio Maria Dal Fabbro, Celina de almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-18T14:46:35Z (GMT). No. of bitstreams: 1 Silva_MarcosValerioGebrada_M.pdf: 5359194 bytes, checksum: e831ae3ea9b56a4d77ebb1a53f2352da (MD5) Previous issue date: 2011 / Resumo: A medição de sólidos tridimensionais tem recebido uma grande atenção da comunidade científica, devido à sua ampla gama de aplicações. Como por exemplo, no controle de qualidade industrial, na medição do corpo humano para aplicações de ergonomia, e muitas outras áreas. Porém existem diversos métodos e técnicas para se obter tais medições, este trabalho demonstra a técnica de moiré que é uma técnica sem contato e não destrutiva, com um rápido processo de digitalização cujos fenômenos de Franjas de Moiré são o resultado da subtração da projeção de grades sobre um certo objeto com relação as grades projetadas em um plano referencial. Possui medição precisa comparável com a de outros sistemas. Demonstra também a exatidão das técnicas de moiré, sendo dado maior enfoque na técnica de moiré de projeção com deslocamento de fase, e pela utilização de dois tipos de grades a de Ronchi e senoidal, onde são observados os possíveis erros das diversas técnicas de moiré e por outros métodos metrológicos. Neste trabalho foi comprovado o melhor desempenho dos tipos e variação da frequência de grades incluindo vários exemplos práticos da sua aplicação em sólidos regulares e irregulares (frutos), comparação com outras técnicas em vários problemas em engenharia agrícola e determinação volumétrica de sólidos regulares e irregulares. Emprego de "softwares" gratuitos o qual também foi uma preocupação para disseminação da técnica, tais como ImageJ, RisingSun Moiré, SCILAB/SIP e rotinas / Abstract: Measurement of three-dimensional solids has received great attention from the scientific community due to its wide range of applications. As examples in can be mentioned industrial quality control, human body measurement applied to ergonomics and many other areas. The pertinent literature discloses several methods and techniques to carry three dimensional measurements. Moiré technique is a group of non-contact and non-destructive methods based on the more phenomena which fringes are the result of the subtraction of the grid projected onto the surface under study and the grid projected onto a reference plane. Moiré methods are yield accurate measurements if compared to other measuring systems. This work was foccused on the projection moiré technique with phase shift, and the use of two types of grids named Ronchi and sinusoidal one. Metrological errors of various techniques as compared with the moiré method have been determined as well. This work demonstrated the best performance of grid frequency variation through several practical applied to regular and irregular solids (fruits). Body dimensions were compared with convention techniques as water immersion and calypper. The application of free software such as ImageJ, RisingSun Moire, Scilab / SIP and routines was considered very useful to reach the final results / Mestrado / Maquinas Agricolas / Mestre em Engenharia Agrícola

Recent applications in three-dimensional (3-D) presentation of information has emphasized the use of field-sequential stereoscopic CRT displays. The usefulness of stereopsis to present depth information has been studied in terms of performance measures such as search time, search accuracy, and subjective image quality ratings. Few, if any, studies have been conducted to investigate the influence of stereopsis upon cognitive workload. This dissertation is a description of two experiments using 3-D images presented on a Tektronix SGS 620 field-sequential stereoscopic CRT. Comparisons were made between presentations incorporating monocular cues only (2 1/2-D) and scenes containing monocular cues plus retinal disparity (3-D). In the first experiment, 11 participants were required to make inter-elements distance judgments under conditions of varying perspective angle, scene complexity, and depth cues while performing an interval production task. Accuracy was found to be significantly enhanced by the addition of retinal disparity as well as by decreases in the complexity of the presented scene. Cognitive workload increased significantly with increases in scene complexity, but no significant difference in workload was found between the stereoscopic and non-stereoscopic presentation formats. The second experiment investigated the effects of stereopsis on target identification under varying conditions of background complexity, target coding schemes, number of elements, signal-to-noise ratio, and depth cues. Accuracy measures, response time, and workload ratings were degraded by increases in scene background complexity, signal:noise ratio, and number of elements. Target coding methods which incorporated color were found to be significantly better than those in which targets were identified by shape only. No significant difference was found between 2 1/2-D and 3-D presentation for any of the dependent measures. The results indicate that retinal disparity it most appropriate for tasks, such as determination of object location in depth, in which the additional information provided by the depth cue is directly related to the task. Retinal disparity provides the most benefit for depth judgment tasks involving highly complex scenes. In cases of very simple tasks or simple scenes, the addition of retinal disparity is contra-indicated. / Ph. D.

Based on an analysis of the existing literature, we extracted important features regarding 3D file organization and layout. In this way, three separate 3D file browsing techniques were evaluated in a comparison study. Block3D uses a priority weighting scheme to elevate and display files in a grid-based structure. Cluster3D uses sets of animated racks to display files. TreeCubePlus3D visualizes files and directories using groups of semi-transparent cubes within a larger cube-like structure. Across all techniques, each file was represented as a thumbnail image of the file's image, document or document with pictures data. The thumbnails were also augmented with meta-information such as filename and relevancy information to simulate a realistic search. Our experiment explores the effectiveness of each 3D file browsing technique in a manual file searching task. Our evaluation is based on task completion time and a post-questionnaire used to gather subjective feedback on each technique in terms of user preference. The results indicate that users completed the manual file search task significantly faster using Block3D than both TreeCubePlus3D and Cluster3D. Subjective ranking also showed users preferred the Block3D technique.

Shape plays an important role in our everyday life to interpret information about the surroundings whether we are aware or not. Together with visual and auditory information, we are able to obtain and process information for different purposes. Output devices such as monitors and speakers convey visual and auditory information while input devices such as touch screen and microphones receive that information for human machine interaction. Such devices have become commonplace but there has yet to be a fitting input/output device utilizing our haptic perception. Digital Clay is a next generation Human Machine Interface (HMI) device for 2.5D shape input/output via an array of hydraulic actuators. This device potentially has wide applications in the areas of engineering, sciences, medicine, military, entertainment etc. The user can perceive the shape of a computer programmed model in a tangible and concrete manner which means an added realism with the addition of the sense of touch. Conversely, the user can also use Digital Clay as an input device to the computer, by shaping and molding desired shapes on the device, no longer limited to drawing models with a mouse on CAD software. Shape display has been achieved with the current 5x5 prototype at the Georgia Institute of Technology but this research seeks to expand its capability to include haptic feedback and consequently shaping mode. This thesis gives an overview of the current 5x5 prototype and implements 2 commonly used haptic control methods, the admittance control and the impedance control. For implementing the admittance control, actuator displacement and velocity controllers and a proportional integral observer (PIO) are designed. The model-based unknown input observer is a solution for force estimation without added sensors in the actuators. For implementing the impedance control, a novel pressure control technique is designed to provide pressure feedback to the actuators array along with accurate and reliable displacement measurement. Both of the haptic control methods are evaluated, hardware and software limitations are outlined and possible future improvements are suggested.

Thesis (MSc (Computer Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The aim of this thesis is to develop a generic 3D virtual environment development platform for autism spectrum disorder (ASD) therapy tools. The potential of using computerised therapy tools for ASD therapy is well known. However, the development of such tools is expensive and time-consuming, and is language and culture speci c. This work intends to alleviate these problems. The design of the platform is based on known game engine designs, but adapted for the requirements of ASD therapy tools. It supports standard features such as 3D rendering, animation and audio output. Speci c features, aimed at ASD therapy tools and educational games, included in our engine are: replays, data capturing, remote monitoring over a network and language localisation. We also implemented an input hardware abstraction layer to allow support for non-standard input peripherals in the future, without modifying existing game implementations. Furthermore, to separate the development of games and tools from the engine, we include wrapper libraries in our engine for Lua and Java. We successfully developed our engine and implemented a number of prototype therapy tools and educational games. These implementations confirmed that the engine works as expected. Some of these programs are currently in use at a local primary school. / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is om 'n 3D virtuele omgewing en ontwikkelingsplatform vir outistiese spektrum versteuring (OSV) terapiemiddels te ontwikkel. Die gebruik van rekenaargebaseerde terapiemiddels vir OSV terapie is bekend. Om sulke terapiemiddels te ontwikkel is egter duur, tydrowend en is dikwels gerig op spesi eke taal- en kultuurgroepe. Hierdie werk het dit ten doel om hierdie probleme te bowe te kom. Die ontwerp van die platform is gebaseer op die ontwerp van bekende videospeletjie-enjins, maar is aangepas vir die benodigdhede van OSV terapiemiddels. Dit ondersteun standaard funksionaliteit soos 3D uitbeelding, animasie en klank. Ons platform sluit in spesi eke funksionaliteit, wat gerig is op OSV terapiemiddels en opvoedkundige speletjies, naamlik: kykweer, datavaslegging, afstandswaarneming oor 'n netwerk en taal-lokalisering. Verder is 'n abstrakte koppelvlak vir toevoerapparatuur ontwikkel, wat dit moontlik maak om in die toekoms nie-standaard toevoerapparatuur te ondersteun, sonder om bestaande speletjies se implementasies aan te pas. Verder, om die ontwikkeling van speletjies en terapiemiddels te skei van die enjin, is koppelvlakke ontwikkel wat dit moontlik maak om die enjin in Lua en Java te gebruik.