Spindulių trasavimas ir padalijimo paviršiai yra svarbūs įrankiai realistiškai atrodantiems vaizdams generuoti. Padalijimas – tai algoritmas, leidžiantis gauti glotnius paviršius pakartotinai dalijant gardeles. Spindulių trasavimas yra technologija, kuri remiasi apšvietimo skaičiavimu. Jos dėka galima gauti atspindžius, permatomumą, spindulių lūžimą kertant skaidrius objektus, taipogi realistiškus šešėlius. Mūsų darbo tikslas buvo suderinti šiuos du metodus, kuriant programinę priemonę, kuri leistų gauti sudėtingų objektų idealiai glotnius aukštos kokybės realistiškus vaizdus. Siekdami to, mes pritaikėme ir tokias kompiuterinės grafikos technologijas, kaip dengimas tekstūromis ir tūrių algebra. / Ray tracing and subdivision surfaces are important tools for generating realistic looking images. Subdivision is an algorithmic technique to generate smooth surfaces as a sequence of successively refined polyhedral meshes. Ray tracing is a technique that performs global calculations of lighting and shading, reflection and transmission of light, casting of shadows, and other effects. The basic idea behind ray tracing is to follow the paths of light rays around a 3-D scene. Our goal is generation of a high-quality realistic images by combining these two techniques. We also implemented other computer graphics methods designed to increase image realism (Texture Mapping) and to simplify modeling process (Boolean operations with solids).

This thesis develops and demonstrates an approach for estimating the three-dimensional (3D) location of a vocalizing underwater marine mammal using acoustic arrival time measurements at three spatially separated receivers while providing rigorous location uncertainties. To properly account for uncertainty in the measurements of receiver parameters (e.g., 3D receiver locations and synchronization times) and environmental parameters (water depth and sound speed correction), these quantities are treated as unknowns constrained with prior estimates and prior uncertainties. While previous localization algorithms have solved for an unknown scaling factor on the prior uncertainties as part of the inversion, in this work unknown scaling factors on both the prior and arrival time uncertainties are estimated. Maximum a posteriori estimates for sound source locations and times, receiver parameters, and environmental parameters are calculated simultaneously. Posterior uncertainties for all unknowns are calculated and incorporate both arrival time and prior uncertainties. Simulation results demonstrated that, for the case considered here, linearization errors are generally small and that the lack of an accurate sound speed profile does not necessarily cause large uncertainties or biases in the estimated positions. The primary motivation for this work was to develop an algorithm for locating underwater Pacific walruses in the coastal waters around Alaska. In 2009, an array of approximately 40 underwater acoustic receivers was deployed in the northeastern Chukchi Sea (northwest of Alaska) from August to October to record the vocalizations of marine mammals including Pacific walruses and bowhead whales. Three of these receivers were placed in a triangular arrangement approximately 400 m apart near the Hanna Shoal (northwest of Wainwright, Alaska). A sequence of walrus knock vocalizations from this data set was processed using the localization algorithm developed in this thesis, yielding a track whose estimated swim speed is consistent with current knowledge of normal walrus swim speed. An examination of absolute and relative walrus location uncertainties demonstrated the usefulness of considering relative uncertainties for applications where the precise location of the mammal is not important (e.g., estimating swim speed). / Graduate

Successful integration of daylighting systems requires the ability to predict their performance for given climates. In this dissertation, a bottom-up approach is applied to evaluate the optical performance of a selection of daylighting systems. The evaluations are based on the optical properties of the included materials, and part of the dissertation focuses on developing new optical characterization methods. The work on characterization techniques uses an integrating sphere method to characterize the transmittance of light scattering samples more accurately. The method's principle is to reduce the discrepancy in light distribution between the reference and the sample scans by using an entry port beam diffuser. For samples exhibiting distinct light scattering patterns, the benefits of improved uniformity outweigh the errors introduced by the diffusing material. The method is applicable to any integrating sphere instrument, and its simplicity makes it suitable for standard measurements. In addition to normal-hemispherical properties, many daylighting applications require knowledge of the system's spatial light distribution. This dissertation presents a method combining experimental techniques and ray tracing simulations to assess the light distribution from a Venetian blind system. The method indicates that ray tracing based on simplified optical data is inadequate to predict the light distribution for slat materials exhibiting both specular and diffuse properties. Ray tracing is a promising complement to experimental methods used to characterize light guiding or light redirecting systems. Here, spectrophotometric measurements of a scaled mirror light pipe validate a ray tracing model. The model shows excellent agreement with experimental results for both direct and diffuse incident light. The spectral evaluation shows no dramatic color changes for the transmitted light. The ray tracing model is used to evaluate four daylighting systems for a selection of Swedish locations. The percentage of occupied time when the studied systems achieve full design illuminance is relatively low, but the systems provide a valuable contribution to the required illuminance. Additionally, this dissertation provides an overview of available energy efficient windows and illustrates the importance of including the solar energy transmittance when evaluating window energy performance. Overall, this dissertation presents optical characterization techniques for improved performance evaluations of daylighting systems.

The use of High-Frequency (HF) radio-wave propagation in the ionosphere remains prevalent for applications such as long-range communication, target detection and commercial broadcasting. The ionosphere presents a challenging channel for radio-wave propagation as it is a varying medium dependent on a number of external factors. Of the many adverse effects of ionospheric propagation, signal fading is one of the most difficult to eliminate due to its unpredictable nature. Increase in the knowledge of how the ionospheric channel affects the propagating signals, in particular fading of the signals, will drive the continual improvements in the reliability and performance of modern wide-bandwidth HF systems. This is the underlying motivation for the study of signal fading of HF radio-waves propagating through the ionosphere, from both the theoretical and experimental perspectives, with the focus of application to modern wide bandwidth HF systems. Furthermore, it is the main objective of this investigation to address the lacking in the current literature of a simple analytical signal fading model for wideband HF systems that relates the physics of the ionospheric irregularities to the observable propagation effects due to the irregularities, and one that is verified by experimental observations. An original approach was taken in the theoretical investigation to develop an analytical model that combines the effects of signal fading and directly relating them to the ionospheric irregularities that are causing the fading. The polarisation fading model (PFM) is a combination of geometric optics, perturbation techniques and frequency offset techniques to derive expressions for the Faraday rotation of the radio-wave propagating in the ionosphere. Using the same notation as the PFM, the amplitude fading model (AFM) extends the Complex Amplitude concept using perturbation techniques and Green’s functions solution to arrive at a set of expressions that describes the focussing and defocussing effects of the wave. The PFM and AFM, together with expressions for combining the effects of multiple propagation paths, provide a simple analytic model that completely describes the fading of the signal propagating in the ionosphere. This theoretical model was implemented into an efficient ionospheric propagation simulator (IPS) from which simulations of wide bandwidth HF signals propagating through the ionosphere can be undertaken. As an example of the type of results produced by the IPS, for a typical 1200km path in the north-south direction with the ionospheric channel under the influence of a travelling ionospheric disturbance (TID), a 10 MHz radio-wave signal in one-hop path is shown to be affected by polarisation fading with fading periods in the order of minutes, and a fading bandwidth in the order of 100 kHz. Further results generated by the IPS have shown to be consistent with the results reported elsewhere in the literature. The experimental investigation involves the study of signal fading from observations of real signals propagating in the ionosphere, a major part of which is the development of a digital compact channel probe (CCP) capable of operating in dual-polarisation mode, and the characterisation of such systems to ensure that data collected are not compromised by the non-idealities of the individual devices contained within the system. The CCP was deployed in experiments to collect transmissions of HF frequency-modulated continuouswave (FMCW) radio signals from the Jindalee Over-the-Horizon radar (OTHR) in dualpolarisation. Analyses of the collected data showed the full anatomy of fading of signals propagating in the ionosphere for both horizontal and vertical polarisations, the results of which are consistent with that from the IPS and thus verifying the validity of the theoretical model of fading. Further experimental results showed that in majority of the observations polarisation fading is present but can be masked by multi-path fading, and confirming that periods of rapid signal fading are associated with rapid changes in the ionospheric channel. From the theoretical and experimental investigations, the major achievement is the successful development of an efficient propagation simulator IPS based on the simple analytical expressions derived in the PFM and AFM theoretical models of signal fading, which has produced sensible signal fading results that are verified by experimental observations. One of the many outcomes of this investigation is that polarisation diversity has the potential to bring improvements to the quality of wide-bandwidth HF signals in a fading susceptible propagation channel. The combination of an efficient propagation simulator IPS based on theoretical signal fading model and the experimental data collection by the dual-polarisation CCP is a major step in allowing one to fully understand the different aspects of fading of signals propagating in the ionosphere, which sets a solid foundation for further research into the design of wide bandwidth HF systems and the possible fading mitigation techniques. / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 78-81).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references and index.

Techn. University, Diss., 2004--Braunschweig.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Airborne seeker antennas are usually enclosed within a dielectric radome for protection against their harsh operational environment. However the presence of a radome can introduce serious degrading effects on the radiation and electrical performance of the enclosed antenna. The degradation effect studied in this report is that of Bore Sight Error (BSE). BSE is a squint in the pointing accuracy of the antenna due to the enclosing radome. A ray-tracing approach is presented that is able to analyse the BSE of seeker radomes in general and is especially suited to electrically large radomes where other computational electromagnetic techniques become overly computationally intensive. The ray-tracing algorithm is wrapped in a GUI which, given the radome, antenna, polarisation and incidence plane parameters will compute the BSE for any set of requested scan angles. Close agreement was obtained with measured BSE performance available in literature. Due to easy setup and fast computation time it is demonstrated that the GUI can be efficiently used for iterative radome design and optimisation. / AFRIKAANSE OPSOMMING: Luggedrae soekantennes is normaalweg omhul binne ‘n dielektriese antennekoepel vir beskerming teen ‘n strawwe omgewing. Die teenwoordigheid van ‘n antennakoepel kan egter ernstige nadelige effekte op die straling en elektriese werkverrigting van die omhulde antenne hê. Die nadelige effek wat in hierdie verslag ondersoek word, is dié van die “Bore Sight Error (BSE).” BSE is ‘n afwyking in die akkuraatheid van die antenna se rigtingwysing as gevolg van die antennakoepel. Straal-natrekking wat die BSE van soek-antennekoepels in die algemeen kan analiseer word beskryf. Hierdie tegniek is veral gepas vir elektries groot antennekoepels waar die berekenige vir EM tegnieke te intensief raak. Die straalnatrekkingsalgoritme word omvat in ‘n grafiese gebruikerskoppelvlak. Gegee die parameters van die antennekoepel, antenne, polarisasie en invallende vlak, sal die BSE vir enige stel skandeerhoeke bereken word. Goeie ooreenstemming was verkry, vergeleke met gemete BSE vanuit die literatuur. Die eenvoudige opstel van die koppelvlak en vinnige berekeningstyd wys daarop dat die koppelvlak doeltreffend gebruik kan word vir iteratiewe antennekoepel ontwerp en optimering.

BARRETO, Isaac Moreira. Cálculo do fator-de-forma exato entre áreas diferencial e finita usando CSG. 2008. 62 f. Dissertação (Mestrado em ciência da computação)- Universidade Federal do Ceará, Fortaleza-CE, 2008. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-07-11T16:45:40Z No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2016-07-18T13:45:29Z (GMT) No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) / Made available in DSpace on 2016-07-18T13:45:29Z (GMT). No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) Previous issue date: 2008 / The Ray-Tracing and Radiosity methods are the main representatives of the method that solve the global illumination problem. In both mthods it is necessary to know the energy tranfer ratio between two areas. This ratio, called form factor, is one of the key concepts in Radiosity methods and is being more frequently used in Ray-Tracing methods with finite area light sources. There are many methods for the computation of the form factor, most of them are approximative due to a matter of performance, but, in some specific cases, the extra computational effort needed to compute the exact value of the form factor can improve the overall performance of the illumination method. In general, in these cases, the computational effort needed to obtain an acceptable approximation of the form factor outweighs the effort necessary to compute the exact value. Furthermore there are situation, for example, shadow boundary shading, in which a high precision is far more important than a performance gain. In this work we present a method to compute the exact form factor between a finite area and a differential area which uses CSG techniques to identify the ooccluded areas of the source. / Os métodos de Ray-Tracing e Radiosidade são os principais representantes dos métodos existentes para resolver o problema de iluminação global. Em ambos os métodos se faz necessário saber a taxa de transferência de energia luminosa entre duas áreas. Essa taxa de transferência, chamada de fator-de-forma, é um dos pontos principais no método de Radiosidade e vem sendo usado cada vez com mais frequência em métodos de Ray-Tracing com fontes luminosas de área finita. Existem vários métodos para o cálculo do fator-de-forma, a maioria deles são aproximativos por uma questão de desempenho. Porém, em casos específicos, o trabalho extra para calcular o valor exato do fator-de-forma pode melhorar o desempenho global do método. Em geral, nesses casos, o esforço necessário para se obter uma aproximação aceitável do valor do fator-de-forma supera o esforço necessário para calcular o valor exato em si. Além disso, existem situações, tais como a renderização nas áreas de fronteiras de sombras, em que uma alta precisão é mais importante do que um ganho no desempenho. Nessas situações, é desejável que o método tenha ao seu dispor uma maneira de calcular o valor exato do fator-de-forma. Neste trabalho é apresentado um método para calcular o fator-de-forma exato entre uma área finita e uma área diferencial que utiliza de técnicas CSG para identificar as áreas ocluídas do polígono emissor.

Les ondes de type choeur sont parmi les ondes électromagnétiques les plus intenses observées dans la magnétosphère interne de la Terre, et jouent un rôle crucial dans la dynamique des ceintures de radiation terrestres qui est un enjeu majeur de la météorologie de l’espace. Elles sont en effet responsables de l’accélération et la perte des électrons énergétiques qui peuplent notamment la ceinture externe. Or, les satellites ne peuvent couvrir entièrement la magnétosphère interne, et les données de ces ondes sont pauvres dans certaines régions. Le but de cette thèse est donc de pouvoir compléter les données satellites par le biais des simulations numériques, en déterminant les distributions statistiques des ondes de type choeur dans la magnétosphère interne. Pour cela, un code dit de traçage de rayons a été développé, incluant un modèle réaliste de magnétosphère interne. La propagation des ondes choeur par le biais de ce code est d’abord décrite dans ce travail, mettant notamment l’accent sur l’importance de l’angle azimutal des ondes. Puis, en utilisant la base de données de trajectoires réalisée pour des paramètres typiques des choeurs sources, la reconstruction des distributions statistiques mesurées par Cluster est présentée. Il est ainsi démontré l’invalidité, aux moyennes et hautes latitudes, de l’approximation quasi-longitudinale utilisée dans de nombreux calculs de la dynamique des ceintures de radiation. En se basant sur ces distributions réalistes d’angles normaux, mais aussi d’amplitude des ondes, il est ensuite démontré l’importante différence obtenue sur les pertes d’électrons énergétiques. Par la suite, la précision de nos simulations numériques pour l’étude des ondes choeurs réfléchies dans la magnétosphère est mise en évidence, ainsi que leur importance étant donné le peu d’observations. Nos simulations indiquent notamment que les tons descendants d’ondes choeur peuvent provenir de la réflexion magnétosphérique de tons montants. / Chorus type whistler waves are one of the most intense electromagnetic waves observed in the Earth’s inner magnetosphere, and play a crucial role in the dynamics of radiation belts which is a critical issue in space weather. They are indeed responsible for acceleration and loss of the energetic electron population that shape the outer belt. As spacecraft trajectories cannot entirely cover the inner magnetosphere, satellite measurements are poor in some regions. The aim of this thesis is thus to be able to complete observational data making use of numerical simulations, by determining the statistical distributions of chorus waves in the inner magnetosphere. In order to achieve this aim, a ray tracing code has been developed, including a realistic model of the inner magnetosphere. First, wave propagation by means of this program is described in this work, emphasizing notably the significance of wave azimuthal angle. Then, making use of the trajectory database computed for typical source chorus parameters, the reconstruction of statistical distributions recorded on Cluster spacecraft is presented. It is thereby demonstrated that quasi-longitudinal approximation, used in numerous simulations of radiation belts dynamics, is no longer valid at medium and high latitudes. Taking these realistic distributions as a basis, it is then demonstrated the major discrepancy obtained for energetic electrons losses. Subsequently, the accuracy of our numerical simulations for the study of magnetospherically reflected chorus waves is highlighted, as well as their importance due to the lack of observational data. Our simulations notably indicate that falling tone chorus emissions can originate from the magnetospheric reflection of rising tone elements.