Ces travaux s'inscrivent dans la thématique de l'inférence géométrique dont le but est de répondre au problème suivant : étant donné un objet géométrique dont on ne connaît qu'une approximation, peut-on estimer de manière robuste ses propriétés? On se place dans cette thèse dans le cas où l'approximation est un nuage de points ou un ensemble digital dans un espace euclidien de dimension finie. On montre tout d'abord un résultat de stabilité d'un estimateur de normale basé sur l'analyse en composante principale, ainsi qu'un résultat de convergence multigrille d'un estimateur du Voronoi Covariance Measure qui utilise des matrices de covariance de cellules de Voronoi. Ces deux résultats, comme la plupart des résultats en inférence géométrique, utilisent la stabilité de la fonction distance à un compact. Cependant, la présence d'un seul point aberrant suffit pour que les hypothèses des résultats de stabilité ne soient pas satisfaites. La distance à une mesure est une fonction distance généralisée introduite récemment qui est robuste aux points aberrants. Dans ce travail, on généralise le Voronoi Covariance Measure à des fonctions distances généralisées et on montre que cet estimateur appliqué à la distance à une mesure est robuste aux points aberrants. On en déduit en particulier un estimateur de normale très robuste. On présente également des résultats expérimentaux qui montrent une forte robustesse des estimations de normales, courbures, directions de courbure et arêtes vives. Ces résultats sont comparés favorablement à l'état de l'art. / The purpose of geometric inference is to answer the following problem : Given a geometric object that is only known through an approximation, can we get a robust estimation of its properties? We consider in this thesis the case where the approximation is a point cloud or a digital set in a finite dimensional Euclidean space. We first show a stability result for a normal estimator based on the principal component analysis, as well as a result of multigrid convergence of an estimator of the Voronoi covariance measure, which uses covariance matrices of Voronoi cells. As most of geometric inference results, these two last results use the robustness of the distance function to a compact set. However, the presence of a single outlier is sufficient to make the assumptions of these results not satisfied. The distance to a measure is a generalized distance function introduced recently, that is robust to outliers. In this work, we generalize the Voronoi Covariance Measure to generalized distance functions and we show that this estimator applied to the distance to a measure is robust to outliers. We deduce a very robust normal estimator. We present experiments showing the robustness of our approach for normals, curvatures, curvature directions and sharp features estimation. These results are favorably compared to the state of the art.

Shape-based matching (SBM) is a method for matching objects in greyscale images. It extracts edges from search images and matches them to a model using a similarity measure. In this thesis we extend SBM to find the tilt and height position of the object in addition to the z-plane rotation and x-y-position. The search is conducted using a scale pyramid to improve the search speed. A 3D matching can be done for small tilt angles by using SBM on height data and extending it with additional steps to calculate the tilt of the object. The full pose is useful for picking objects with an industrial robot. The tilt of the object is calculated using a RANSAC plane estimator. After the 2D search the differences in height between all corresponding points of the model and the live image are calculated. By estimating a plane to this difference the tilt of the object can be calculated. Using the tilt the model edges are tilted in order to improve the matching at the next scale level. The problems that arise with occlusion and missing data have been studied. Missing data and erroneous data have been thresholded manually after conducting tests where automatic filling of missing data did not noticeably improve the matching. The automatic filling could introduce new false edges and remove true ones, thus lowering the score. Experiments have been conducted where objects have been placed at increasing tilt angles. The results show that the matching algorithm is object dependent and correct matches are almost always found for tilt angles less than 10 degrees. This is very similar to the original 2D SBM because the model edges does not change much for such small angels. For tilt angles up to about 25 degrees most objects can be matched and for nice objects correct matches can be done at large tilt angles of up to 40 degrees.

Considerando-se os projetos didáticos propostos por Lerner como um recurso para se conciliarem propósitos didáticos e comunicativos em classes de alfabetização, a presente pesquisa teve por objetivo compreender como o trânsito entre conceber, planejar e executar subsidia os professores na construção de sua prática pedagógica de projetos didáticos. Partindo de uma concepção interacionista de aprendizagem, e dialógica de língua, sustentadas por referenciais teóricos como Piaget, Vygotsky, Bakhtin, Ferreiro e Lerner, e apoiando-se também na triangulação didática proposta por Chevallard, o estudo pautou-se em três eixos de investigação: o aluno e seus processos de aprendizagem, a língua como objeto de ensino e a didática dos professores. Cada um deles foi analisado em três instâncias: concepções, intencionalidades e práticas. Trata-se de um estudo de três casos, visando acompanhar o trabalho de professoras de 1º, 2º e 3º ano do Ensino Fundamental. Suas concepções, nos três eixos, foram aferidas através de entrevistas semiestruturadas. As intencionalidades foram inferidas a partir da análise documental dos planejamentos cedidos pelas docentes. A análise das práticas deu-se através de observações não participantes em sala de aula. Os dados foram analisados sob a óptica do paradigma do indiciário proposto por Ginzburg. Concluiu-se neste trabalho que o processo de construção de concepções docentes é híbrido e marcado por diferentes referências que circulam na esfera educacional, com diversos níveis de apropriação. Os dados coletados demonstraram que, além da concepção em que se fundam, diferentes elementos do contexto escolar interferem nas intencionalidades e planejamentos dos professores. A prática pedagógica, por sua vez, embora receba a influência das concepções e intencionalidades docentes, oscila em função de uma multiplicidade de fatores internos e externos. Com isso, a pesquisa demonstrou o processo de construção didática docente e trouxe novos elementos à reflexão sobre as abordagens de formação inicial e continuada dos professores. Além disso, evidenciou a necessidade de iniciativas que possam ampliar a produção de conhecimento didático e, ainda, promover a reflexão dos docentes sobre o próprio trabalho, em especial sobre as práticas de alfabetização e os projetos didáticos. / Considering Lerners concept of project-based teaching as a resource to conciliate didactic and communicative purposes in literacy grades, this research aims to understand how the transition between conceiving, planning and executing scaffolds project-based teaching and supports teachers practice. Taking a dialogic and interactionist perspective of the language, sustained by theoretical references as Piaget, Vygotsky, Bakhtin, Ferreiro and Lerner, as well as Chevallards didactic triangulation, this study explores three main paths: the student and his/her learning processes, the language as a teaching object and the teachers didactics. Each path was analysed in the following aspects: conceptualization, intentionality and praxis, aiming to consider the daily work of first, second and third grade teachers in Elementary School. Semistructured interviews were used to look into the teachers concepts. Intentionality was observed through the document analysis of the teachers planners. Non-participant class observation methods were used to analyse the teachers daily practice. All collected data was considered under the perspective of the evidential paradigm proposed by Ginzburg. This dissertation came to the conclusion that the process of building concepts performed by teachers is multiple, including various references regarding the educational environment as a whole. The material analysed has proved that different school contexts impact not only teachers planners, but also their intentionality. Hence, the pedagogical practice oscillates according to countless internal and external factors. This dissertation contributes to the reflection about these variables and brings new elements to approach initial and continuing training for teachers. Besides that, it hightlights the need for initiatives that may broaden the production of didactic knowledge and enhance the reflection on ones pedagogical practice, especially regarding literacy routines and project-based teaching.

In this thesis spacetime analysis is applied to laser triangulation in an attempt to eliminate certain artifacts caused mainly by reflectance variations of the surface being measured. It is shown that spacetime analysis do eliminate these artifacts almost completely, it is also shown that the shape of the laser beam used no longer is critical thanks to the spacetime analysis, and that in some cases the laser probably even could be exchanged for a non-coherent light source. Furthermore experiments of running the derived algorithm on a GPU (Graphics Processing Unit) are conducted with very promising results. The thesis starts by deriving the theory needed for doing spacetime analysis in a laser triangulation setup taking perspective distortions into account, then several experiments evaluating the method is conducted.

A laser-triangulating range camera uses a laser plane to light an object. If the position of the laser relative to the camera as well as certrain properties of the camera is known, it is possible to calculate the coordinates for all points along the profile of the object. If either the object or the camera and laser has a known motion, it is possible to combine several measurements to get a three-dimensional view of the object. Camera calibration is the process of finding the properties of the camera and enough information about the setup so that the desired coordinates can be calculated. Several methods for camera calibration exist, but this thesis proposes a new method that has the advantages that the objects needed are relatively inexpensive and that only objects in the laser plane need to be observed. Each part of the method is given a thorough description. Several mathematical derivations have also been added as appendices for completeness. The proposed method is tested using both synthetic and real data. The results show that the method is suitable even when high accuracy is needed. A few suggestions are also made about how the method can be improved further.

An investigation was initiated, targeting snapshot 3D image sensors, with the objective to match the speed and resolution of a scanning sheet-of-light system, without using a scanning motion. The goal was a system capable of acquiring 25 snapshot images per second from a quadratic scene with a side from 50 mm to 1000 mm, sampled in 512×512 height measurement points, and with a depth resolution of 1 µm and beyond. A wide search of information about existing 3D measurement techniques resulted in a list of possible schemes, each presented with its advantages and disadvantages. No single scheme proved successful in meeting all the requirements. Pulse modulated time-of-flight is the only scheme capable of depth imaging by using only one exposure. However, a resolution of 1 µm corresponds to a pulse edge detection accuracy of 6.67 fs when visible light or other electromagnetic waves are used. Sequentially coded light projections require a logarithmic number of exposures. By projecting several patterns at the same time, using for instance light of different colours, the required number of exposures is reduced even further. The patterns are, however, not as well focused as a laser sheet-of-light can be. Using powerful architectural concepts such as matrix array picture processing (MAPP) and near-sensor image processing (NSIP) a sensor proposal was presented, designed to give as much support as possible to a large number of 3D imaging schemes. It allows for delayed decisions about details in the future implementation. It is necessary to relax at leastone of the demands for this project in order to realise a working 3D imaging scheme using concurrent technology. One of the candidates for relaxation is the most obvious demand of snapshot behaviour. Furthermore, there are a number of decisions to make before designing an actual system using the recommendations presented in this thesis. The ongoing development of electronics, optics, and imaging schemes might be able to meet the 3D snapshot demands in a near future. The details of light sensing electronics must be carefully evaluated and the optical components such as lenses, projectors, and fibres should be studied in detail.

The goal of learning interventions is to prepare an individual to acquire knowledge, skills and attitudes that will enable him/her to perform better and to be able to handle all the challenges posed by the continuous changing world of work. Transfer of learning to the workplace provides a yardstick to determine whether the goal has been attained or not. This study was conducted to answer the following questions; what is transfer of learning, what constraints have been identified in the existing research on transfer of learning, and what constraining factors prevent management trainees to transfer learning to the workplace in a private sector case study. To answer these questions a mixed research approach (qualitative and quantitative) was used. Triangulation of data was done to ensure reliability. The questionnaire was designed using the Likert rating scale and was used as a quantitative data collection tool for this study. The data was displayed through line and pie graphs for graphical illustrations. The questionnaire was analysed using a hand tabulation data coding table. The questionnaire was distributed to all 34 management trainees and only 17 completed the questionnaires. The qualitative data collection tools consisted of semi-structured and focus group interviews. The literature study pointed out that various researchers identified factors that prevent transfer of learning. The factors are; lack of organisational support, course content that is dissociated from the trainees’ roles and responsibilities in the workplace, trainees’ willingness and readiness. The empirical research findings revealed that organisational factors such as lack of coaching, feedback, mentoring as well as creating an opportunity for trainees to implement the skills and knowledge play a leading role while training and learner factors play a contributing role as constraints to transfer of learning to the workplace. / Dissertation (MEd (Maximising Potential))--University of Pretoria, 2006. / Curriculum Studies / unrestricted

Representações computacionais de formas podem ser criadas em ferramentas CAD ou geradas a partir de um objeto físico já existente. Esta última abordagem oferece como vantagens rapidez e fidelidade ao objeto original, que são os aspectos fundamentais em muitas aplicações, como Simulações Numéricas de Equações Diferenciais Parciais e Imagens Médicas. A reconstrução (ou geração de malhas superficiais) a partir de pontos amostrados de uma superfície de um objeto é um problema clássico de representação de formas. Nesta dissertação apresentamos um vasto levantamento bibliográfico deste tipo de reconstrução, classificando e descrevendo os principais trabalhos presentes na literatura. A partir do levantamento bibliográfico, selecionamos um conjunto de algoritmos sobre os quais foram realizadas comparações teóricas e empíricas cujos resultados são apresentados. Para finalizar, apresentamos aplicações de nossas implementações em Simulação Numérica de Equações Diferenciais Parciais e processamento de Imagens / Computational representations of shapes can be developed using CAD applications or created from data acquired from a real physical object. This latter is advantageous with respect to time and fidelity to the original object which are essential to several applications, such as Numerical Simulation of Partial Differential Equations and Medical Imaging. A classical shape representation problem is that of reconstruction (or superficial mesh generation) from points sampled over the surface of an object. In this Master\'s thesis we describe a broad survey of these reconstruction methods. We focus in the classification and characterization of the main algorithms proposed in the literature. From this survey, we selected some algorithms and conducted some theoretical and practical comparisons. We conclude this work describing applications of the algorithms implemented in Numerical Simulations of Differential Partial Equations and Image Processing

Procedural content generation inom spel refererar till algoritmiskt, procedurellt skapande av digitalt innehåll i syfte att automatisera och minska mängden arbete för designers och grafiker. Ett område procedural content generation används för inom spel är dungeon generering. Målet för detta arbete var att utforska en 2D algoritm som används i spelet TinyKeep för just generering av dungeons och se hur den algoritmen kunde prestera om den modifierades för generering i en 3D rymd. Den modifierade algoritmen utvärderades baserat på attributen variation, justerbarhet, pålitlighet samt tidseffektivitet. Resultatet visade visade att det är möjligt att använda algoritmen i spelet TinyKeep i en 3D-rymd med godtagbart prestationsresultat. Som värst visade den modifierade algoritmen på en viss svaghet angående genereringstid vid en större tom rymd med större antal rum hos en dungeon. För framtida arbete vore det intressant att dela upp av delar av den modifierade algoritmen på separata trådar. / <p>Det finns övrigt digitalt material (t.ex. film-, bild- eller ljudfiler) eller modeller/artefakter tillhörande examensarbetet som ska skickas till arkivet.</p>

Practical laser triangulation sessions were performed for each measurement object to obtain ground truth data. Three methods for laser line simulations were implemented: reshaping the built-in light sources of Blender, creating a texture projector and approximating a Gaussian beam as a light emitting volume. The camera simulation was based on the default camera of Blender together with settings from the physical camera. Three approaches for creating wood material were tested: procedural texturing, using microscopic image textures to create 3D-material and UV-mapping high resolution photograph onto the geometry. The blister package was simulated with one material for the pills and another for the semi-transparent plastic packaging. A stand-alone Python script was implemented to simulate anisotropic/directed subsurface scattering of a point laser in wood. This algorithm included an approach for creating vector fields that represented subsurface scattering directions. Three post-processing scripts were produced to simulate sensor noise, blurring/blooming of the laser line and lastly to apply simulated speckle patterns to the laser lines. Sensor images were simulated by rendering a laser line projected onto a measurement object. The sensor images were post-processed with the three mentioned scripts. Thousands of sensor images were simulated, with a small displacement of the measurement object between each image. After post-processing, these images were combined to a single scattering image. SICK IVP AB provided the algorithms needed for laser centre extraction as well as for scattering image creation. / <p>Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska fakulteten, Linköpings universitet</p>