V interaktivních aplikacích jsou stíny tradičně zobrazovány s pomocí algoritmu založeným na stínových mapách. Nevýhodou toho algoritmu je, že stínová mapa, reprezentovaná texturou, má pouze omezené rozlišení. To může vést k nepěkným vizuálním artefaktům objevujících se na hranách stínů. Tato práce představuje postup, který je založen na vylepšené deformaci textury. To umožní zobrazit scénu obsahující složité světelné zdroje, zredukovat artefakty na hranicích stínů a také vylepšit kvalitu stínů bez ohledu na typu scény a její konfiguraci.

Ten-millijoule, thirty-five femtosecond, 800 nm (~40 nm bandwidth) laser pulses are used to study high-order harmonic generation in helium- and neon-filled gas cells of various lengths. Harmonic orders in the range of 50 to 100 are investigated. A semi-infinite cell geometry produces brighter harmonics than cells of sub-centimeter length. In the semi-infinite geometry, the gas occupies the region from the focusing lens to a thin exit foil near the laser focus. Counter-propagating light is used to directly probe where the high harmonics are generated within the laser focus and to investigate phase matching. The phase matching under optimized harmonic generation conditions was found to be unexpectedly good with phase zones many millimeters long. Restricting the laser beam with an 8 mm aperture in front of the focusing lens increases the emission of most harmonic orders observed by as much as an order of magnitude. Optimal harmonic generation pressures were found to be about 55 torr in neon and 110 torr in helium. The optimal position of the laser focus was found to be a few millimeters inside the exit foil of the gas cell. Probing with counter-propagating light reveals that in the case of neon the harmonics are generated in the last few millimeters before the exit foil. In helium, the harmonics are produced over a longer distance. Direct measurement shows that the re-absorption limit for mid-range harmonics in neon has been reached.

Doctor of Philosophy / Department of Industrial & Manufacturing Systems Engineering / Malgorzata J. Rys / This dissertation is the result of studying different methods of increasing guide sign visibility and legibility to drivers during nighttime, to increase safety on roadways. It also studies intersection lighting to indicate the lighting benefits on nighttime crash frequency reduction. From a survey conducted, practices related to overhead guide sign illumination and retroreflectivity in United States were summarized. A laboratory experiment was conducted to compare light distribution of five light sources: Metal Halide, Mercury Vapor, High Pressure Sodium, induction lighting, and Light Emitting Diode (LED). Cost analysis of the five light sources was performed. Combining results of the laboratory experiment and the cost analysis, induction lighting was recommended for states that want to continue external sign illumination. A retroreflectivity experiment was conducted to compare three types of retroreflective sheeting: Engineering Grade (type I), Diamond Grade (type XI), and High Intensity (type IV), to determine the sheeting that best increases visibility and legibility. Diamond Grade (type XI) was found to be the optimal sheeting that increases visibility and legibility to drivers during nighttime. A glare experiment was conducted to expand the retroreflectivity experiment results. Four sheeting-font combinations of High Intensity (type IV) and Diamond Grade (type XI) materials and Series E (Modified) and Clearview fonts were compared. Results revealed an optimal sheeting-font combination of Diamond Grade (type XI) sheeting and Clearview font which increases the visibility and legibility of guide signs to drivers under presence of oncoming glare source. The Highway Safety Information System (HSIS) database was used to study the effect of intersection lighting on the expected crash frequency. Illuminated intersections showed 3.61% and 6.54% decrease in the expected nighttime crash frequency as compared to dark intersections in Minnesota and California, respectively. In addition, partial lighting at intersections decreases the expected nighttime crash frequency by 4.72% compared to continuous lighting in Minnesota. The recommended sheeting-font combination for Departments of Transportation was Diamond Grade (type XI) and Clearview. This combination will increase signs’ visibility and legibility to drivers, and consequently increase safety on roadways. Adding partial lighting at intersections will reduce the expected nighttime crash frequency, and increase safety on roadways.

On peut atteindre des images réalistes par la simulation du transport lumineuse avec des méthodes de Monte-Carlo. La possibilité d’utiliser des sources de lumière réalistes pour synthétiser les images contribue grandement à leur réalisme physique. Parmi les modèles existants, ceux basés sur des cartes d’environnement ou des champs lumineuse sont attrayants en raison de leur capacité à capter fidèlement les effets de champs lointain et de champs proche, aussi bien que leur possibilité d’être acquis directement. Parce que ces sources lumineuses acquises ont des fréquences arbitraires et sont éventuellement de grande dimension (4D), leur utilisation pour un rendu réaliste conduit à des problèmes de performance.Dans ce manuscrit, je me concentre sur la façon d’équilibrer la précision de la représentation et de l’efficacité de la simulation. Mon travail repose sur la génération des échantillons de haute qualité à partir des sources de lumière par des estimateurs de Monte-Carlo non-biaisés. Dans ce manuscrit, nous présentons trois nouvelles méthodes.La première consiste à générer des échantillons de haute qualité de manière efficace à partir de cartes d’environnement dynamiques (i.e. qui changent au cours du temps). Nous y parvenons en adoptant une approche GPU qui génère des échantillons de lumière grâce à une approximation du facteur de forme et qui combine ces échantillons avec ceux issus de la BRDF pour chaque pixel d’une image. Notre méthode est précise et efficace. En effet, avec seulement 256 échantillons par pixel, nous obtenons des résultats de haute qualité en temps réel pour une résolution de 1024 × 768. La seconde est une stratégie d’échantillonnage adaptatif pour des sources représente comme un "light field". Nous générons des échantillons de haute qualité de manière efficace en limitant de manière conservative la zone d’échantillonnage sans réduire la précision. Avec une mise en oeuvre sur GPU et sans aucun calcul de visibilité, nous obtenons des résultats de haute qualité avec 200 échantillons pour chaque pixel, en temps réel et pour une résolution de 1024×768. Le rendu est encore être interactif, tant que la visibilité est calculée en utilisant notre nouvelle technique de carte d’ombre (shadow map). Nous proposons également une approche totalement non-biaisée en remplaçant le test de visibilité avec une approche CPU. Parce que l’échantillonnage d’importance à base de lumière n’est pas très efficace lorsque le matériau sous-jacent de la géométrie est spéculaire, nous introduisons une nouvelle technique d’équilibrage pour de l’échantillonnage multiple (Multiple Importance Sampling). Cela nous permet de combiner d’autres techniques d’échantillonnage avec le notre basé sur la lumière. En minimisant la variance selon une approximation de second ordre, nous sommes en mesure de trouver une bonne représentation entre les différentes techniques d’échantillonnage sans aucune connaissance préalable. Notre méthode est pertinence, puisque nous réduisons effectivement en moyenne la variance pour toutes nos scènes de test avec différentes sources de lumière, complexités de visibilité et de matériaux. Notre méthode est aussi efficace par le fait que le surcoût de notre approche «boîte noire» est constant et représente 1% du processus de rendu dans son ensemble. / Realistic images can be rendered by simulating light transport with Monte Carlo techniques. The possibility to use realistic light sources for synthesizing images greatly contributes to their physical realism. Among existing models, the ones based on environment maps and light fields are attractive due to their ability to capture faithfully the far-field and near-field effects as well as their possibility of being acquired directly. Since acquired light sources have arbitrary frequencies and possibly high dimension (4D), using such light sources for realistic rendering leads to performance problems.In this thesis, we focus on how to balance the accuracy of the representation and the efficiency of the simulation. Our work relies on generating high quality samples from the input light sources for unbiased Monte Carlo estimation. In this thesis, we introduce three novel methods.The first one is to generate high quality samples efficiently from dynamic environment maps that are changing over time. We achieve this by introducing a GPU approach that generates light samples according to an approximation of the form factor and combines the samples from BRDF sampling for each pixel of a frame. Our method is accurate and efficient. Indeed, with only 256 samples per pixel, we achieve high quality results in real time at 1024 × 768 resolution. The second one is an adaptive sampling strategy for light field light sources (4D), we generate high quality samples efficiently by restricting conservatively the sampling area without reducing accuracy. With a GPU implementation and without any visibility computations, we achieve high quality results with 200 samples per pixel in real time at 1024 × 768 resolution. The performance is still interactive as long as the visibility is computed using our shadow map technique. We also provide a fully unbiased approach by replacing the visibility test with a offline CPU approach. Since light-based importance sampling is not very effective when the underlying material of the geometry is specular, we introduce a new balancing technique for Multiple Importance Sampling. This allows us to combine other sampling techniques with our light-based importance sampling. By minimizing the variance based on a second-order approximation, we are able to find good balancing between different sampling techniques without any prior knowledge. Our method is effective, since we actually reduce in average the variance for all of our test scenes with different light sources, visibility complexity, and materials. Our method is also efficient, by the fact that the overhead of our "black-box" approach is constant and represents 1% of the whole rendering process.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-03-03T11:35:25Z No. of bitstreams: 1 fernandojosenogueira.pdf: 4981583 bytes, checksum: 8b3c5698410b92cb533a1907a012d6a6 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-04-24T01:41:50Z (GMT) No. of bitstreams: 1 fernandojosenogueira.pdf: 4981583 bytes, checksum: 8b3c5698410b92cb533a1907a012d6a6 (MD5) / Made available in DSpace on 2016-04-24T01:41:50Z (GMT). No. of bitstreams: 1 fernandojosenogueira.pdf: 4981583 bytes, checksum: 8b3c5698410b92cb533a1907a012d6a6 (MD5) Previous issue date: 2013-02-28 / Este trabalho tem como objeto principal a avaliação experimental de diodos emissores de luz (ou LEDs, do inglês Light Emitting Diodes) quando empregados em luminárias comerciais destinadas aos sistemas de iluminação pública. São apresentados os aspectos gerais da iluminação pública no Brasil, os principais componentes empregados e uma discussão sobre a adoção da tecnologia LED na iluminação de exteriores. Também são abordados os conceitos básicos de fotometria clássica e da fotometria adaptada para baixos níveis de luminância, que leva em consideração a resposta dinâmica visual do olho humano. Para efeito comparativo, o trabalho também inclui uma revisão das principais fontes de luz brancas orientadas à iluminação pública, e. g. lâmpada de vapor metálico, lâmpada de vapor de mercúrio e, mais recentemente, os LEDs. Tal estudo ampara-se em ensaios de laboratório e em campo tomando como base a lâmpada de vapor de sódio em alta pressão, a mais utilizada atualmente no segmento de iluminação de vias públicas. Algumas normativas referentes à aplicação de LEDs em iluminação pública são discutidas e, a partir das recomendações existentes nas normas NBR 16026 e NBR IEC 61347-2-13, são realizados ensaios de pré-conformidade em amostras comerciais de luminárias LED orientadas à iluminação pública do mercado nacional. Além dos ensaios de pré-conformidade, são realizados ensaios de funcionamento das luminárias LED quando expostas a condições críticas de temperatura com o objetivo de se avaliar as mudanças elétricas e fotométricas que ocorrem nestas condições. É apresentada uma metodologia de projeto luminotécnico para instalação de luminárias LED em vias públicas baseando-se na norma de iluminação pública NBR 5101 (revisão 2012), e o acompanhamento do projeto piloto de iluminação pública empregando luminárias LED implantado no anel viário da faculdade de engenharia da Universidade Federal de Juiz de Fora. Durante nove meses foram coletados dados de características elétricas e fotométricas a fim de se averiguar o desempenho destas luminárias em campo. Por fim, foi feito um estudo comparativo entre o antigo sistema de iluminação com lâmpadas de vapor de sódio e o atual, empregando luminárias LED. / The purpose of this research is the experimental evaluation of light emitting diodes (or LEDs) when used in commercial luminaires for street lighting systems. The general aspects of Brazilian public lighting, the main components used and a discussion about the adoption of the LED technology in outdoor lighting are presented. Also, the basic concepts of classical photometry and photometry’s adaptations for low luminance levels are addressed. It takes into consideration the dynamic response of the human eye. For comparative purposes, this research also includes a review of the main white light sources used on public lighting, e.g. Metal Halide Lamp, High Pressure Mercury Vapour Lamp and, recently, the LEDs. Such research is supported by laboratory and on-site studies based on High Pressure Sodium Vapour Lamp; currently, the most used on public lighting system. Some standards regarding LEDs usage on public lighting are discussed and, based on the existing recommendations, regulated by the Brazilian standards NBR 16026 and NBR IEC 61347-2-13, pre-certification studies of commercial LED luminaires samples oriented to public lighting on the home market are performed. Other than the pre-certification studies, additional studies of LED luminaires functioning when exposed to critical conditions of temperature with the intention to evaluate the electric and photometric changes that occur in this circumstances are performed. It is introduced a luminotechnical project methodology for LED luminaires installation on public roads based on the Brazilian standards of public lighting NBR 5101 (reviewed in 2012) and the accompanying of the pilot project of public lighting using LED luminaires implanted on the ring road of the School of Engineering of the Juiz de Fora Federal University. During nine months, data of electric and photometric features were collected in order to investigate the performance of the luminaires on-site. Finally, a comparative study was done between the previous lighting system with High Pressure Sodium Vapour Lamp and the current, using LED luminaires.

To investigate quantum confinement effects on silicon (Si) light source electroluminescence (EL) properties like quantum efficiency, external power efficiency and spectral emission, thin Si finger junctions with nanometre-scale dimensions were designed and manufactured in a fully customized silicon-on-insulator (SOI) semiconductor production technology. Since commonly available photolithography is unusable to consistently define and align nanometre-scale line-widths accurately and electron-beam lithography (EBL) by itself is too time-expensive to expose complete wafers, the wafer manufacturing process employed a selective combination of photolithography and EBL. The SOI wafers were manufactured in the clean-rooms of both the Carl and Emily Fuchs Institute for Microelectronics (CEFIM) at the University of Pretoria (UP) and the Georgia Institute of Technology’s Microelectronic Research Centre (MiRC), which made a JEOL JBX-9300FS electron-beam pattern generator (EPG) available. As far as is known this was the first project in South Africa (and possibly at the MiRC) that employed EBL to define functional nanometre-scale semiconductor devices. Since no standard process recipe could be employed, the complete design and manufacturing process was based on self-obtained equipment characterization data and material properties. The manufacturing process was unprecedented in both the CEFIM and MiRC clean-rooms. The manufacture of nanometre-scale Si finger junctions not only approached the manufacturing limits of the employed processing machinery, but also had to overcome undesirable physical effects that in larger-scale semiconductor manufacture usually are negligible. The device design, mask layout and manufacturing process therefore had to incorporate various material, equipment limitation and physical phenomena like impurity redistribution occurring during the physical manufacturing process. Although the complicated manufacturing process allowed many unexpected problems to occur, it was expected that at least the simple junction breakdown devices be functional and capable of delivering data regarding quantum confinement effects. Although due to design and processing oversights only 29 out of 505 measured SOI light sources were useful light emitters, the design and manufacture of the SOI light sources was successful in the sense that enough SOI light sources were available to conduct useful optical characterization measurements. In spite of the fact that the functional light sources did not achieve the desired horizontal (width) confinement, measured optical spectra of certain devices indicate that vertical (thickness) confinement had been achieved. All spectrometer-measured thickness-confined SOI light sources displayed a pronounced optical power for 600 nm < λ < 1 μm. The SOI light source with the highest optical power output emitted about 8 times more optical power around λ = 850 nm than a 0.35 μm bulk-CMOS avalanche light-source operating at the same current. Possible explanations for this effect are given. It was shown that the buried oxide (BOX) layer in a SOI process could be used to reflect about 25 % of the light that would usually be lost to downward radiation back up, thereby increasing the external power efficiency of SOI light sources. This document elaborates on the technical objectives, approach, chip and process design, physical wafer manufacture, production process control and measurement of the nanometre-scale SOI light sources. Copyright / Dissertation (MEng)--University of Pretoria, 2010. / Electrical, Electronic and Computer Engineering / unrestricted

This diploma thesis concerns with problematic of modern intelligent wiring systems in buildings, meanwhile presents their advantages against old classical wiring systems. Also deals with utilization and properties of modern components for regulation, switching and light controlling. The first part deals with light sources and possible ways how to control the power of individual luminary sources. The second part discuss about utilization of radio-frequency systems in new buildings and also in reconstructions. In the next part is described a possibility of bus system for controlling building illumination scope with focusing to control system Nikobus. The last part is concerned on technical-economical evaluation of intelligent wiring systems by various manufacturers according to specific requirements.

This diploma thesis deals with the definition of solar lights for solar purposes and solar simulators. These concepts are presented and described in detail. The theoretical part is described below chapter explaining the possibilities of using solar energy phototherapy. The next section follows the issue of standards and their podnorem AM, describes in detail the direct and diffuse light component. In connection continues with IEC 60904, IEC 60904-3 and IEC 60904-9, differences in purpose and use. The thesis describes the problems of the methods of analysis of the solar spectrum as defined in IEC 60904-9. In the penultimate chapter we discuss all light sources, their properties and uses. They navyzují selected light sources used in this work, as well as descriptions and color filters designed for measurement and subsequent evaluation in the practical part. The last chapter analyzes used measuring instruments, their advantages and disadvantages. In the practical part, we describe a method for measuring real-world light spectra, determining compliance with these spectra spectra AM 1.5 and the necessity to generate data from IEC 60904-3. Another part allows measured data to see in an understandable form and must include an assessment and assignment of the data set into classes according to AM 1.5.

This master’s thesis deals with properties of a solar radiation, measurement of a solar spectrum and standard IEC 60904-9, which defines the requirements for a solar simulator. Solar simulators are classified as A, B or C for each of the three categories based on criteria of spectral distribution match, irradiance non-uniformity on the test plane and temporal instability. The goal of this thesis was creation software for automatic evaluation of a solar spectrum. Software was created in Matlab application and its function is to determine class of solar spectral match with spectrum AM1.5. The last part contains a measurement of various solar sources and using the created software was determined its spectral match with spectrum AM1.5.

This paper is focused on realistic rendering of interior environments with varying lighting conditions. It proposes methods of setting properties of light sources to achieve a specific scene appearence. It mainly works with light comming from a sky and sun to the scene and describes this light in relation to weather conditions, time of day and overcast factor. The goal is creating easily configurable system in which a single parameter change leads to significant change of lighting conditions. All these changes should be presented in a short video.