Abstract The colours of objects perceived by a colour camera are dependent on the illumination conditions. For example, when the prevailing illumination condition does not correspond to the one used in the white balancing of the camera, the object colours can change their appearance due to the lack of colour constancy capabilities. Many methods for colour constancy have been suggested but so far their performance has been inadequate. Faces are common and important objects encountered in many applications. Therefore, this thesis is dedicated to studying face colours and their robust use under real world illumination conditions. The main thesis statement is "knowledge about an object's colour, like skin colour changes under different illumination conditions, can be used to develop more robust techniques against illumination changes". Many face databases exist, and in some cases they contain colour images and even videos. However, from the point of view of this thesis these databases have several limitations: unavailability of spectral data related to image acquisition, undefined illumination conditions of the acquisition, and if illumination change is present it often means only change in illumination direction. To overcome these limitations, two databases, a Physics-Based Face Database and a Face Video Database were created. In addition to the images, the Physics-Based Face Database consists of spectral data part including skin reflectances, channel responsivities of the camera and spectral power distribution of the illumination. The images of faces are taken under four known light sources with different white balancing illumination conditions for over 100 persons. In addition to videos, the Face Video Database has spectral reflectances of skin for selected persons and images taken with the same measurement arrangement as in the Physics-Based Face Database. The images and videos are taken with several cameras. The databases were used to gather information about skin chromaticities and to provide test material. The skin RGB from images were converted to different colour spaces and the result showed that the normalized colour coordinate was among the most usable colour spaces for skin chromaticity modelling. None of the colour spaces could eliminate the colour shifts in chromaticity. The obtained chromaticity constraint can be implemented as an adaptive skin colour modelling part of face tracking algorithms, like histogram backprojection or mean shift. The performances of these adaptive algorithms were superior compared to those using a fixed skin colour model or model adaptation based on spatial pixel selection. Of course, there are cases when the colour cue is not enough alone and use of other cues like motion or edge data would improve the result. It was also demonstrated that the skin colour model can be used to segment faces and the segmentation results depend on the background due to the method used. Also an application for colour correction using principal component analysis and a simplified dichromatic reflection model was shown to improve colour quality of seriously clipped images. The results of tracking, segmentation and colour correction experiments using the collected data validate the thesis statement.

An Investigation into Red Emitting Phosphors for Display and Lightings Two very different classes of red phosphors were evaluated in this thesis; sulphide based phosphors (CaS:Eu2+) and phosphors based on the formulae:- LiEu1- xMx(MoO4)2-y(WO4)y, [M=Al3+, Y3+ and Gd3+]. CaS:Eu2+ was coated with Al2O3 using atomic layer deposition technique and placed into a humidity chamber at high temperature and high humidity for a period of time. The emission spectra were measured and evaluated against uncoated CaS:Eu2+. The results from the humidity tests revealed that Al2O3 coated CaS:Eu2+ increased the life span of the phosphor and therefore can be the potential use for the purpose of application at moderate humidity and temperature. For the phosphors based on LiEu1-xMx(MoO4)2-y(WO4), all the findings reported herein showed that, depending upon the types of cations introduced to the host lattices, incorporation of M at some point offered very much the same or better luminous efficacy when compared to the parent compound with 100 mol% of Eu3+. This work also attempted to examine the correlative relationship between the crystal structures and the luminous efficacies although some attempts were unsuccessful. The findings discovered within this research are beneficial for solid state lighting industries where the cost of using rare earth metals has become significant and recycling is difficult.

La simulation des réflexions lumineuses multiples à l'intérieur d'un environnement nécessite de résoudre une intégrale de premier ordre, récursive infinie, pour laquelle il n'existe pas de solution analytique dans le cas général. Certaines méthodes permettent de donner une solution théorique exacte, mais avec des temps de calcul trop important pour espérer produire plusieurs images par seconde dans un avenir proche. De nombreuses méthodes permettent de réaliser ces calculs de manière plus rapide, mais elles reposent sur des approximations dont les effets sont souvent visibles sur les images produites. Notre objectif est de proposer des solutions permettant de réduire les erreurs de calculs en exploitant deux approches complémentaires : (i) une homogénéisation des termes de l'équation de manière à la résoudre seulement à l'aide de quelques opérateurs simples ; (ii) la prise en compte précise des informations de visibilité pour réduire le biais des méthodes reposant sur une estimation de densité. A terme, notre objectif est de diminuer le coût des requêtes de visibilité de nos deux contributions. Pour cela nous envisageons notamment d'introduire des calculs hiérarchiques de visibilité de façon à amortir le coût global des requêtes. / Simulating light transfer within a virtual environment requires to solve a first order, infinite recursive integral, that unfortunately doesn't have any solution in general cases. Though theoretically exact solutions exist, their computing time is not adapted to real-time rendering in a near future. Many methods have been proposed for accelerating these computations, but they rely on approximations that often produce visible artifacts on the resulting images. Our goal is to propose some new solutions that can reduce biases with two complementary approaches : (i) a new homogeneous representation of each term of the equation can be used to resolve it using only simple operators ; (ii) considering precise visibility information in order to reduce bias of methods that rely on density estimation. On the long range, we aim at reducing visibility requests costs of each contribution. For that purpose, we particularly plan to introduce hierarchical visibility computations so as to amortize queries cost.

Hatchling disorientation after emergence is a major factor impacting sea turtle populations. This study utilized data from over 1,200 Florida Fish and Wildlife Conservation Commission (FWC) Marine Turtle Disorientation Report forms from years 2006 to 2011 to assess changes in the severity and locations of disorientation events and the impact of municipal beach lighting ordinances. While the FWC forms were completed for all sea turtle species observed, this study focused only on loggerhead sea turtles (Caretta caretta). A Disorientation Severity Index (DSI) was derived from the number of hatchlings and the direction of their tracks leaving the nests to evaluate the changes in disorientation over six years in Broward County. The FWC forms provide a much larger database for the analysis of hatchling disorientation patterns and trends than can be derived from the more precise, but labor intensive, Hatchling Orientation Index (HOI) survey method of Witherington et al. (1996). This research differs from prior work by focusing on the information provided in the FWC Marine Turtle Disorientation Report forms; using each individual disorientation to assess changes in the severity of hatchling disorientations over time. Prior work has not used the FWC forms for analysis. Significant differences were found for average DSI between years and locations. Overall, DSI decreased significantly from 2006 to 2011 in Hillsboro Beach, Pompano Beach, Lauderdale-by-the-Sea, Fort Lauderdale, and Hollywood. This might be due to increased compliance with lighting ordinances. In addition, disorientation hotspots were identified and the DSI in these hotspots decreased significantly in central and south Fort Lauderdale, Pompano Beach, and Lauderdale-by-the-Sea. Hotspots were visually identified as R-Zone ranges with higher numbers of disorientations than in other ranges (Fig. 6). Artificial beach illumination is very prevalent in Broward County. However, there was no significant relationship between the number of types of lights that were recorded on the FWC forms and DSI. Disorientations seemed to be clustered within hotspots with known lighting issues. Management strategies should use these analyses to reassess loggerhead recovery plans to reduce disorientation hotspots and increase hatchling recruitment.

Master of Science / Department of Architectural Engineering and Construction Science / Raphael A. Yunk / Today's engineers of building lighting systems must maintain a careful balance between the demands of accepted standards of practice, the necessity of life safety, the system performance needs of the client, and the developing national energy standards and certifications gaining prominence in the public eye. These sources of influence on the design process can create conflicts between the pressing need to conserve system energy usage and a costlier and perhaps unacceptable end-result for the client. In this climate, various governmental organizations and industry cooperatives have been funding published research and case-studies in order to promote sustainable design practices. Within these publications are repeated references to a "Task-Ambient" lighting fixture layout strategy. Multiple recent publications cite profound energy-saving benefits attainable using this design method. However, there is a noticeable lack of measured data concerning other qualities of this layout scheme, such as the end-user's comfort and ability to perform tasks under the resulting light distributions. Whether this lack of data resulted from the added complexity associated with such non-numerical measurements, or for some other unknown reason, this report explores this gap in the available data. An extended survey procedure was developed to approach the problem of measuring these unknown qualities of the Task-Ambient design strategy. This involved constructing multiple physical lighting layout mockups, defining the features of the Task-Ambient strategy which necessitated measurement, and designing objective tasks tailored to measure each of these non-numerical qualities. The careful analysis of this study's data results yields trends indicative of the Task-Ambient strategy, relative to a standard uniform layout, adversely affecting productivity, concentration, and the participants' subjective perceptions of the space's light distribution. The lowered level of energy use was however affirmed. The implications of these results are that the Task-Ambient strategy, while an efficient method of lighting system layout design, may not be beneficial for the client in other respects.

Two billion people world-wide use kerosene-burning lamps for household lighting. These lamps produce large quantities of soot. In Chapter 2, I describe our field study examining 230 people in rural Uganda. I show that kerosene lamps are a major source of smoke exposure in the developing world, and that replacing such lamps with solar-powered lights reduces indoor soot levels 17-fold, leading to significant improvements in health within months. This finding is particularly notable because respiratory disease is the #1 cause of death in children under 5 worldwide. Because solar cells are a challenge to manufacture in the developing world, I next examined the potential of harvesting electrons from soil-based microbes as a source of clean energy. Such devices are known as microbial fuel cells (MFCs); because soil is available everywhere, MFCs can, in principle, be locally constructed all over the world. In Chapter 3, I describe our exploration of the biology of MFCs, using high-throughput DNA sequencing to demonstrate a role for genus Pseudomonas in energy production. I also examine numerous agricultural products available throughout the developing world to determine whether any could serve as a suitable ‘feed’ for MFC soil. I find that dried animal blood increases MFC energy production 10-fold. In Chapter 4, I describe our design of a modular, stackable MFC, demonstrate that it can be easily constructed in rural Africa, and use it to power lights and to charge a cell phone battery.

La simulation d'éclairage est un processus qui s'avère plus complexe (temps de calcul, coût mémoire, mise en œuvre complexe) aussi bien pour les matériaux brillants que pour les matériaux lambertiens ou spéculaires. Afin d'éviter le calcul coûteux de certains termes de l'équation de luminance (convolution entre la fonction de réflexion des matériaux et la distribution de luminance de l'environnement), nous proposons une nouvelle structure de données appelée Source Surfacique Équivalente (SSE). L'utilisation de cette structure de données nécessite le pré-calcul puis la modélisation du comportement des matériaux soumis à divers types de sources lumineuses (positions, étendues). L'exploitation d'algorithmes génétiques nous permet de déterminer les paramètres des modèles de BRDF, en introduisant une première source d'approximation. L'approche de simulation d'éclairage utilisée est basée sur un cache de luminance. Ce dernier consiste à stocker l'éclairement incident sous forme de SSE en des points appelés enregistrements. Durant la simulation d'éclairage, l'environnement lumineux doit également être assimilé à un ensemble de sources surfaciques équivalentes (en chaque enregistrement) qu'il convient de définir de manière dynamique. Cette phase constitue une deuxième source d'erreur. Toutefois, l'incertitude globale ne se réduit pas au cumul des approximations réalisées à chaque étape. Les comparatives réalisées prouvent, au contraire, que l'approche des Sources Surfaciques Équivalentes est particulièrement intéressante pour des matériaux rugueux ou pour les matériaux très brillants placés dans des environnements relativement uniformes. L'utilisation de SSE a permis de réduire considérablement à la fois le coût mémoire et le temps de calcul. Une fois que les SSE sont calculés en chaque enregistrement et pour un certain nombre de points de vue, nous proposons une nouvelle méthode de visualisation interactive exploitant les performances des GPU (carte graphique) et s'avérant plus rapide que les méthodes existantes. Enfin nous traiterons le cas où les grandeurs photométriques sont spectrales, ce qui est très important lorsqu'il s'agit de réaliser des simulations d'éclairage précises. Nous montrerons comment adapter les zones d'influence des enregistrements en fonction des gradients de luminance et de la géométrie autour des enregistrements. / Radiance caching methods have proven efficient for global illumination. Their goal is to compute precisely illumination values (incident radiance or irradiance) at a reasonable number of points lying on the scene surfaces. These points, called records, are stored in a cache used for estimating illumination of other points in the scene. Unfortunately, with records lying on glossy surfaces, the irradiance value alone is not sufficient to evaluate the reflected radiance; each record should also store the incident radiance for all incident directions. Memory storage can be reduced with projection techniques using spherical harmonics or other basis functions. These techniques provide good results with low shininess BRDFs. However, they get impractical for shininess of even moderate value since the number of projection coefficients increase drastically. In this paper, we propose a new radiance caching method, that handles highly glossy surfaces, while requiring a low memory storage. Each cache record stores a coarse representation of the incident illumination thanks to a new data structure called Equivalent Area light Sources (EAS), capable of handling fuzzy mirror surfaces. In addition, our method proposes a new simplification of the interpolation process since it avoids the need for expressing and evaluating complex gradients. Moreover, we propose a new GPU based visualisation method which exploits these EAS data structure. Thus, interactive rendering is done faster than existing methods. Finally, physical ligting simulations need to manipulate spectral physical quantities. We demonstrate in our work how these quantities can be handle with our technic by adapting the record influence zone depending on the radiance gradients and the geometry around the records.

A iluminação cênica é uma das mais fecundas áreas da prática teatral contemporânea, sendo responsável por muitos aspectos da construção dos sentidos na cena, e da fruição da obra pelos espectadores. Essa pesquisa visa jogar luzes sobre as estratégias utilizadas por alguns iluminadores na articulação de seu trabalho com as necessidades da fabulação de diferentes tipos de espetáculos e seus respectivos espaços. Numa encenação a demanda de responsabilidade que recai sobre o trabalho do iluminador é imensa. No geral ele precisa, além de iluminar o ator e a cena, de alguma maneira também iluminar o texto e a obra da encenação, ressaltando suas intencionalidades expressivas e de comunicação. Muitas vezes seu trabalho é o ponto de convergência ou confrontação entre os diversos profissionais envolvidos numa montagem teatral, além de contribuir de forma absoluta na maneira como o espectador recebe e experimenta um espetáculo. Acreditamos que tais e tamanhas tarefas poderão receber algumas luzes com o estudo que esta pesquisa pretende contemplar, com objetivo de contribuir para uma elaboração didática para interessados no tema. / The stage lighting is one of the most fruitful areas of the practice of contemporary theater, being responsible for many aspects of the construction of meanings in the scene, and to the enjoyment of the play by the spectators. This research aims to light up the strategies used for some light designers in the articulation betwen its work and the necessities of the report in differents types of spectacles and its respective spaces. On stage, the responsibility demands that falls in the work of the light designer is immense. In general terms, it needs, beyond lighting the actor and the scene, in some way also to light up the text and the mise-en-scène, to show its expressives purposes and comunication intents. Many times its work is the convergence point or confrontation among the involved professionals in a stage setting, beyond contribute in all the ways that the spectator receives and tries the spectacle. We believe that such and so great tasks will be able to receive some light with the study that this research intends to contemplate, with objective to contribute for a didactic elaboration for interested in the subject.

A estimação da iluminação é essencial para aplicações de realidade mista que se propõem a integrar elementos virtuais a cenas reais de maneira harmoniosa e sem a perda do realismo. Um dos métodos mais utilizados para fazer essa estimação é conhecido como iluminação baseada em imagens (Image Based Lighting - IBL), método que utiliza light probes para capturar a intensidade da iluminação incidente em uma cena. Porém, IBL estima a iluminação incidente apenas para um determinado instante e posição. Nesta dissertação, será avaliado um modelo de iluminação que utiliza séries temporais de imagens de light probes, obtidas de maneira esparsa em relação ao tempo, para renderizar cenas em instantes arbitrários. Novas cenas contendo objetos virtuais poderão ser renderizadas utilizando imagens de light probes artificiais, geradas a partir das amostras da iluminação originais. Diferentes funções de interpolação e aproximação são avaliadas para modelar o comportamento luminoso. As imagens finais produzidas pela metodologia também são verificadas por voluntários, de modo a determinar o impacto na qualidade de renderização em aplicações de realidade mista. Além da metodologia, foi desenvolvida uma ferramenta de software em forma de plugin para facilitar o uso de IBL temporalmente variável, permitindo assim a renderização realística de objetos virtuais para instantes arbitrários / Lighting estimation is essential for mixed reality applications that strive to integrate virtual elements into real scenes in a seamlessly fashion without sacrificing realism. A widely used method for lighting estimation is known as Image Based Lighting (IBL), which utilizes light probes to determine incident light intensity within a scene. However, IBL estimates light incidence only for a given time and position. In this dissertation, we assess a lighting model based on a time series of light probe images, obtained sparsely, to render scenes at arbitrary times. New scenes containing virtual objects can then be rendered by using artificial light probe images, which are generated from the original light samples. Different types of interpolation and approximation functions were evaluated for modeling lighting behavior. The resulting images were assessed for the impact in rendering quality for mixed reality applications by volunteers. In addition to the methodology, we also developed a software plugin to simplify the use of temporally variable IBL, allowing realistic rendering of virtual objects for arbitrary times

O desenvolvimento urbano recente produziu cidades que frequentemente são inconsistentes com os princípios do crescimento sustentável. Devido ao alto índice de urbanização, ocorrem problemas recorrentes de mobilidade, poluição, carência de áreas verdes e altos custos de infraestrutura. Nesse contexto, a verticalização, tanto para o alto quanto o aproveitamento de espaços subterrâneos, tem o potencial de desenvolver cidades mais compactas e eficientes, reduzindo distâncias devido à maior concentração das funções. Em Porto Alegre, existem propostas em discussão que trazem o uso do subsolo como alternativa, a exemplo de inúmeros projetos pelo mundo onde os espaços subterrâneos são, muitas vezes, considerados atrativos e qualificados pela população. O grande limitador da utilização desses locais é a dificuldade de levar ao subsolo as condições de conforto ambiental e psicológico equivalentes às da superfície, principalmente em relação à forma como a luz é utilizada. Por isso, este trabalho visa levantar a percepção da iluminação em espaços subterrâneos de uma amostra da população de Porto Alegre, com objetivo de verificar o potencial de atratividade desses espaços no contexto local Utilizando a metodologia de estudo de campo, foram selecionadas três passagens subterrâneas na cidade para coletar dados sobre a percepção de uma amostra de usuários - homens ou mulheres, entre 15 e 65 anos - escolhidos de forma aleatória. O estudo considerou variáveis como iluminância, dimensões e revestimentos dos espaços, bem como o tempo de percurso dos usuários. Os dados foram organizados e analisados utilizando os softwares Microsoft Excel 2007, Word Art 2017 e Sigma Plot 13. A pesquisa concluiu que, alinhado com o encontrado na revisão da literatura, os espaços subterrâneos em Porto Alegre são percebidos como locais com características muito negativas. Apesar disso, a maioria dos usuários relatou não sentir falta de contato com o exterior e não se sentir enclausurada, possivelmente pelo fato de as estações serem locais pouco profundos e de fácil acesso à superfície. O estudo de como iluminar subsolos em clima subtropical ainda é incipiente, e espera-se, com este trabalho, ampliar o conhecimento sobre como os usuários de Porto Alegre percebem esses lugares, estimulando a criação de subsolos atraentes e que valorizem a iluminação, fator indispensável para a saúde e bem-estar. / Recent urban development has produced cities that are frequently inconsistent in regard to the principles of sustainable growth. Due to the high level of urbanization, problems pertaining to mobility, pollution, lack of green area and high infrastructure costs are frequent. In this context, verticalization – regarding the use of both elevated and underground spaces – has the potential of developing cities that are more compact and efficient, reducing distances due to a higher concentration of functions. In the city of Porto Alegre, Brazil, there are many proposals currently being discussed that address the use of the underground as an alternative, in light of countless projects around the world in which underground spaces are often considered attractive and valued by the population. The use of these spaces is greatly limited, however, by the difficulty of bringing to the underground the environmental and psychological comfort conditions that are equivalent to those of the surface, especially in relation to how light is employed. Therefore, this work aims to survey the perception of lighting in underground spaces of a sample of Porto Alegre’s population, with the objective of verifying the attractiveness potential of these spaces in the local context. Using a field study methodology, we selected three underground passages in the city in order to collect data on the perception of a sample of male or female users, aged 15 to 65 and chosen at random The study took into account variables such as illuminance, dimensions and protective layers of these spaces, as well as the journey time of the users. The data were organized and analyzed using Microsoft Excel 2007, Word Art 2017 and Sigma Plot 13. The study concluded that, aligned to the results reported in the literature, the underground spaces of Porto Alegre are perceived as having very negative aspects. Nonetheless, most users related not feeling any lack of contact with the outside space and not feeling trapped, possibly because the underground stations are not very deep places and with easy access to the surface. The subject of how to provide lighting to underground spaces in a subtropical climate is still incipient, and we hope, with this study, to contribute to the knowledge of how Porto Alegre’s users perceive these places, fostering the creation of attractive underground spaces and the valuing of lighting, which is essential to human health and wellbeing.