In recent years, unmanned aerial vehicles (UAV), also called drones, have experienced a rapid increase, which leads to the concern of illegal use of them. Passive RF is one of the effective ways to detect drones by receiving drones’ communication signals. After receiving the signal from drones, one can utilize the prior knowledge of signal characteristics for identifying and locating the drones. The angle of arrival (AoA) measured by multiple passive RF sensors can be used for localization by triangulation. However, the accuracy of the AoA measured by the passive RF sensors is strongly affected by the environment. In particular in urban areas, the multipath effect is prominent due to the building blockage and complicated terrestrial conditions that introduce certain errors to the result. So the service provider of the sensors needs a tool to perform the environment analysis to understand the quality of the service. A fast tool that can simulate the sensor network and surrounding environment can offer a flexible solution to optimize the sensor coverage and indicate the blind zone of detection. Especially when the sensors are deployed on the mobile platform, such tool can significantly improve the defensive quality of the drone detection system by optimizing real-time deployment and indicating low observable areas. In order to plan the sensor locations and assess the performance after the deployment of the sensor at a fast speed, We propose a multipath-based model to calculate the AoA error. The model is able to utilize the input of geometrical information for simulating the AoA error within a region. In this thesis, we investigate the outdoor channel at 2.4GHz using the ray-tracing method as it is the most used channel for UAVs. Massive simulations have been carried out and real test flights have been conducted to evaluate the accuracy of the modeling. Both simulations and test flights are carried out in Kista center where buildings are from high-rises to one-floor houses with various heights. In the simulation, the AoA is obtained by MUltiple SIgnal Classification (MUSIC) algorithm. Test flights are conducted using an existing Software-defined radio (SDR) based RF sensor. We tried our best to carry out the same trajectories in both simulations and test flights to provide fair comparisons. The simulation results show that the multipath model can predict the trend of AoA error when the height changes, while not sufficient to predict the error when the 2D position changes. Thus, to more accurately characterize the signal transmission, it is essential to extend this thesis to include more detailed environmental information and adaption based on measurement. / Under de senaste åren har obemannade flygfarkoster (UAV), även kallade drönare, ökat snabbt, vilket leder till oro för olaglig användning av dem. Passiv RF är ett av de effektiva sätten att upptäcka drönare genom att ta emot drönarnas kommunikationssignaler. Efter att ha tagit emot signalen från drönare kan man använda den tidigare kunskapen om signalegenskaperna för att identifiera och lokalisera drönarna. AoA som mäts av flera passiva RF-sensorer kan användas för lokalisering genom triangulering. Noggrannheten hos AoA som mäts av de passiva RF-sensorerna påverkas dock starkt av miljön. Särskilt i stadsområden är multipath-effekten framträdande på grund av byggnadsblockering och komplicerade markförhållanden som medför vissa fel i resultatet. Därför behöver leverantören av sensorer ett verktyg för att utföra miljöanalysen för att förstå tjänstens kvalitet. Ett snabbt verktyg som kan simulera sensornätverket och den omgivande miljön kan erbjuda en flexibel lösning för att optimera sensortäckningen och ange den blinda zonen för upptäckt. Särskilt när sensorerna placeras på en mobil plattformkan ett sådant verktyg avsevärt förbättra drönardetektionssystemets försvarskvalitet genom att optimera utplaceringen i realtid och ange områden med låg observationsgrad. För att planera sensorernas placering och bedöma prestandan efter att sensorn har placerats ut i snabb takt föreslår vi en multipath-baserad modell för att beräkna AoAfelet. Modellen kan utnyttja inmatningen av geometrisk information för att simulera AoA-felet inom ett område. I denna avhandling undersöker vi utomhuskanalen vid 2:4 GHz med hjälp av raytracing- metoden eftersom det är den mest använda kanalen för UAV:er. Massiva simuleringar har utförts och verkliga testflygningar har genomförts för att utvärdera modelleringens noggrannhet. Både simuleringar och testflygningar har utförts i Kista centrum där byggnaderna är allt från höghus till envåningshus med olika höjd. I simuleringen erhålls AoA med hjälp av MUSIC-algoritmen. Testflygningar genomförs med hjälp av en befintlig SDR-baserad RF-sensor. Vi gjorde vårt bästa för att utföra samma banor i både simuleringar och testflygningar för att ge rättvisa jämförelser. Simuleringsresultaten visar att multipathmodellen kan förutsäga trenden för AoA-felet när höjden ändras, medan den inte är tillräcklig för att förutsäga felet när 2D-positionen ändras. För att mer exakt karakterisera signalöverföringen är det därför viktigt att utöka denna avhandling till att omfatta mer detaljerad miljöinformation och anpassning baserad på mätning.

Contact lens performance depends on a number of lens properties. Many metrology systems have been developed to measure different aspects of a contact lens, but none test the surface figure in reflection to subwavelength accuracy. Interferometric surface metrology of immersed contact lenses is complicated by the close proximity of the surfaces, low surface reflectivity, and instability of the lens. An interferometer to address these issues was developed and is described here. The accuracy of the system is verified by comparison of glass reference sample measurements against a calibrated commercial interferometer. The described interferometer can accurately reconstruct large surface departures from spherical with reverse raytracing. The system is shown to have residual errors better than 0.05% of the measured surface departure for high slope regions. Measurements made near null are accurate to lambda/20. Spherical, toric, and bifocal soft contact lenses have been measured by this system and show characteristics of contact lenses not seen in transmission testing. The measurements were used to simulate a transmission map that matches an actual transmission test of the contact lens to lambda/18. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)

This thesis presents a method for simulating fluids on a view dependent grid structure to exploit level-of-detail with distance to the viewer. Current computer graphics techniques, such as the Stable Fluid and Particle Level Set methods, are modified to support a nonuniform simulation grid. In addition, infinite fluid boundary conditions are introduced that allow fluid to flow freely into or out of the simulation domain to achieve the effect of large, boundary free bodies of fluid. Finally, a physically based rendering method known as photon mapping is used in conjunction with ray tracing to generate realistic images of water with caustics. These methods were implemented as a C++ application framework capable of simulating and rendering fluid in a variety of user-defined coordinate systems.

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 work contains a few basic terms of analytical geometry. We mention some of ray-triangle intersection computation algorithms and present some use-case examples. We discuss capabilities of CUDA, optimization techniques of this architecture and implementation with focus on given issues. Algorithms of ray-triangle intersection are tested and results are discussed.

Inom mobilnät är 5G den senaste standarden och förväntas ge möjlighet för nya applikationer och tillämpningar. Den trådlösa kommunikationen för 5G har stor spridning av tillgängliga frekvenser. En utmaning är att de högre frekvenserna, som erbjuder bäst kapacitet, har en kort räckvidd. Detta kan hanteras genom att placera fler anslutningspunkter med korta avstånd. Vanligtvis behöver en person vara på plats för att testa placering av anslutningspunkter på ett sådant sätt att minimal blockering av radiosignaler förekommer. Detta kan vara både kostsamt och tidskrävande. Detta projekt har som mål att utveckla ett strålspårningsprogram för att simulera och visualisera hur en stråle påverkas vid kollision med olika material när den skickas från en anslutningspunkt/sändare till en mottagare. Strålspårningsprogrammet visualiserar i grafikmotorn Unity och simuleringen görs i en strålspårningsmotor baserad på strålspårnings-API:et OptiX. För att uppnå detta mål utfördes undersökning och komplettering av tidigare arbeten, tekniska inklusive teoretiska studier av strålspårnings- och materialinteraktion.Resultatet av arbetet är ett strålspårningsprogram där påverkan på en stråles rörelse vid reflektion och brytning mot objekt med vissa material kan beräknas, som kan användas för att avgöra möjligheten att etablera en anslutning vilket sedan kan visualiseras i Unity. / Within mobile networks, 5G is the latest standard and has a wide range of available frequencies, where a disadvantage of the higher frequencies is that the range is short. This can be counteracted by placing more connection points with short distances between them. Placement of connection points usually requires a person to be on site to test placements, to ensure minimal blocking of radio signals in an area, which can be both costly and time-consuming. This project aims to develop a ray tracing program to visualize how a ray is affected when colliding with different materials when it is sent from a connection point/transmitter to a receiver. This is visualized in the Unity graphics engine, and the simulation is done in a ray tracing engine based on the ray tracing API OptiX. To achieve this goal, previous works were investigated, and technical and theoretical studies of ray tracing and material interaction were conducted. In addition, different software programs relevant to the project were evaluated, including OptiX and Unity. The result of this work is a ray tracing program where the impact on a beam's movement when reflecting and refracting against objects with certain materials can be calculated, which can be used to determine if a connection can be established, and visualization of this can be done in Unity.

We present a technique for out-of-core GPU path tracing of arbitrarily large scenes that is compatible with hardware-accelerated ray-tracing. Our technique improves upon previous works by subdividing the scene spatially into streamable chunks that are loaded using a priority system that maximizes ray throughput and minimizes GPU memory usage. This allows for arbitrarily large scaling of scene complexity. Our system required under 19 minutes to render a solid color version of Disney's Moana Island scene (39.3 million instances, 261.1 million unique quads, and 82.4 billion instanced quads at a resolution of 1024x429 and 1024spp on an RTX 5000 (24GB memory total, 22GB used, 13GB geometry cache, with the remainder for temporary buffers and storage) (Wald et al.). As a scalability test, our system rendered 26 Moana Island scenes without multi-level instancing (1.02 billion instances, 2.14 trillion instanced quads, ~230GB if all resident) in under 1h:28m. Compared to state-of-the-art hardware-accelerated renders of the Moana Island scene, our system can render larger scenes on a single GPU. Our system is faster than the previous out-of-core approach and is able to render larger scenes than previous in-core approaches given the same memory constraints (Hellmuth, Zellman et al, Wald).

This thesis is concerned in the method of realistic rendering using a distributed raytracing. This method simulates various visual effects and generates high realistic 2D images. The work analyses the problem and explains principles of solution related to this technique. There is also descriprion of the method of simple reytracing which provides a basis for the distributed raytracing. A part of work is specialized for optimalization of distributed raytracing.

The Scheimpflug principle was recommended as allowing distortion-free imaging; however, a detailed analysis reveals geometrical errors as well as distortions arising from absorption of light along the optical pathway. Correction formulas and factors will be presented and applied to the biometry of the eye. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Triangle is the mostly used primitive in computer graphics. Calculation of its intersection with a ray has many applications and is often a bottleneck of a program. This work focuses on its usage and various methods of calculation. It tries to combine these techniques to achieve high performance on modern processors.