Shadow Rendering from Omnidirectional Light Sources

Tato práce pojednává o možnostech zobrazení stínů z všesměrových světelných zdrojů za použití knihovny OpenGL. Zejména se zaměřuje na algoritmy Cube map shadow mapping a Dual paraboloid shadow mapping. Dále jsou v práci obsaženy výsledky srovnání implementací těchto algoritmů z hlediska časové náročnosti vytvoření stínové mapy a také z hlediska vizuální kvality stínů.This work discusses the possibilities for shadow rendering from omnidirectional light sources using OpenGL library. In this work the Cube map shadow mapping and the Dual paraboloid shadow mapping algorithms are described. Further more, this work contains the results of a comparison of these two methods in a way of time required for shadow map creation and a comparison of visual quality of resulting shadows.

Shadow Techniques for Interactive and Real-Time Applications

Shadows provide important visual cues for the relative position of objects in threedimensional space. For interactive and real-time applications, e.g. in virtual reality systems or games, the shadow computation needs to be extremely fast, usually synchronized with the displays refresh rate. Using dynamic scenes with many, movable light sources, shadow computation is therefore often the main bottleneck in a rendering system. In this thesis we will discuss this problem in detail: Originating from Williams shadow maps and Crows shadow volumes, we will present hardware accelerated shadow techniques that are able to generate shadows of high-quality while still being fast enough to be used in real-time or interactive applications. We will show algorithms for the computation of hard shadows as well as for the more complex problem of approximating soft shadows caused by area light sources.Schatten sind wichtige visuelle Merkmale die über die relative Position eines Objektes in einem drei-dimensionalen Raum Aufschluss geben. Die Schattenberechnung muss für interaktive und Echtzeit-Anwendungen, wie z.B. Virtual Reality Systeme oder in Spielen, extrem schnell erfolgen, idealerweise synchronisiert mit der Bildwiederholfrequenz. Im Fall von dynamischen Szenen mit vielen, beweglichen Lichtquellen, ist die Berechnung von Schatten oftmals der zeitkritischste Teil innerhalb eines Rendering-Systems. In dieser Dissertation behandeln wir genau dieses Problem im Detail. Ausgehend vonWilliams\u27; Shadow Maps und Crow\u27;s Shadow Volumes werden Hardwarebeschleunigte Schattentechniken vorgestellt, die Schatten von hoher Qualität erzeugen können, aber trotzdem so effizient sind, dass sie für Echtzeit- und interaktive Anwendungen eingesetzt werden können. Wir werden sowohl Algorithmen zur Berechnung harter Schatten beschreiben, als auch das schwierigere Problem der Approximation von sanften Schatten, wie sie z.B. bei Flächenlichtquellen entstehen, behandeln

High-Quality Shadow Rendering from Complex Light Sources

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.In interactive applications, shadows are traditionally rendered using the shadow mapping algorithm. The disadvantage of the algorithm is limited resolution of depth texture which may lead to unpleasant visual artifacts on shadow edges. This work introduces an approach that is based on the improved texture warping. It allows for rendering a scene with the complex light sources, reduce the artifacts on the shadow boundaries and also improve the quality of the shadows regardless of the type of the scene and its configuration.

Rendering of Shadows in a Scene with DirectX

Tato práce pojednává o metodách zobrazení stínů, jejich analýze a implementaci v rozhraní DirectX 11. Teoretická část popisuje historický vývoj použití stínů v 3D aplikácích a jednotlivé algoritmy pro výpočet stínů. V rámci práce jsou na demonstrační aplikaci porovnány zhlediska výkonu, náročnosti implementace a kvality výstupu 2 varianty algoritmu shadow mapping pro všesměrová světla - s využitím cube mappingu a parabolické projekce, každá s pěti různě optimalizovanými implementacemi.This work discusses shadowing methods, analyses them and describes implementation in DirectX 11 API. Theoretical part describes historical evolution of shadow usage in 3D applications and also analyzes shadowing algorithms. This work compares 2 variants of shadow mapping algorithm for omnidirectional lights, based on cube mapping and paraboloid projection, on demo application using quality, performance and implementation aspects.

Fast Non-Linear Projections using Graphics Hardware

http://artis.imag.fr/Publications/2008/GHFP08/International audienceLinear perspective projections are used extensively in graphics. They provide a non-distorted view, with simple computations that map easily to hardware. Non-linear projections, such as the view given by a fish-eye lens are also used, either for artistic reasons or in order to provide a larger field of view, e.g. to approximate environment reflections or omnidirectional shadow maps. As the computations related to non-linear projections are more involved, they are harder to implement, especially in hardware, and have found little use so far in practical applications. In this paper, we apply existing methods for non-linear projections [Lloyd et al. 2006; Hou et al. 2006; Fournier 2005] to a specific class: non-linear projections with a single center of projection, radial symmetry and convexity. This class includes, but is not limited to, paraboloid projections, hemispherical projections and fish-eye lenses. We show that, for this class, the projection of a 3D triangle is a single curved triangle, and we give a mathematical analysis of the curved edges of the triangle; this analysis allows us to reduce the computations involved, and to provide a faster implementation. The overhead for non-linearity is bearable and can be balanced with the fact that a single nonlinear projection can replaces as many as five linear projections (in a hemicube), with less discontinuities and a smaller memory cost, thus making non-linear projections a practical alternative. More at http://artis.imag.fr/Publications/2008/GHFP0

Deployable antenna demonstration project

Test program options are described for large lightweight deployable antennas for space communications, radar and radiometry systems

Many-Light Real-Time Global Illumination using Sparse Voxel Octree

Global illumination (GI) rendering simulates the propagation of light through a 3D volume and its interaction with surfaces, dramatically increasing the fidelity of computer generated images. While off-line GI algorithms such as ray tracing and radiosity can generate physically accurate images, their rendering speeds are too slow for real-time applications. The many-light method is one of many novel emerging real-time global illumination algorithms. However, it requires many shadow maps to be generated for Virtual Point Light (VPL) visibility tests, which reduces its efficiency. Prior solutions restrict either the number or accuracy of shadow map updates, which may lower the accuracy of indirect illumination or prevent the rendering of fully dynamic scenes. In this thesis, we propose a hybrid real-time GI algorithm that utilizes an efficient Sparse Voxel Octree (SVO) ray marching algorithm for visibility tests instead of the shadow map generation step of the many-light algorithm. Our technique achieves high rendering fidelity at about 50 FPS, is highly scalable and can support thousands of VPLs generated on the fly. A survey of current real-time GI techniques as well as details of our implementation using OpenGL and Shader Model 5 are also presented

Microwave performance characterization of large space antennas

Performance capabilities of large microwave space antenna configurations with apertures generally from 100 wavelengths upwards are discussed. Types of antennas considered include: phased arrays, lenses, reflectors, and hybrid combinations of phased arrays with reflectors or lenses. The performance characteristics of these broad classes of antennas are examined and compared in terms of applications

Dynamic conversion of solar generated heat to electricity

The effort undertaken during this program led to the selection of the water-superheated steam (850 psig/900 F) crescent central receiver as the preferred concept from among 11 candidate systems across the technological spectrum of the dynamic conversion of solar generated heat to electricity. The solar power plant designs were investigated in the range of plant capacities from 100 to 1000 Mw(e). The investigations considered the impacts of plant size, collector design, feed-water temperature ratio, heat rejection equipment, ground cover, and location on solar power technical and economic feasibility. For the distributed receiver systems, the optimization studies showed that plant capacities less than 100 Mw(e) may be best. Although the size of central receiver concepts was not parametrically investigated, all indications are that the optimal plant capacity for central receiver systems will be in the range from 50 to 200 Mw(e). Solar thermal power plant site selection criteria and methodology were also established and used to evaluate potentially suitable sites. The result of this effort was to identify a site south of Inyokern, California, as typically suitable for a solar thermal power plant. The criteria used in the selection process included insolation and climatological characteristics, topography, and seismic history as well as water availability

Design and analysis of a quasi-optical beam combiner for the QUBIC CMB interferometer

In winter 2009 a number of physicists met in Paris to discuss the prospect of observing the CMB B-mode polarization using a novel technique called bolometric interferometry. This was the first meeting of what would later become the QUBIC collaboration. In this thesis we discuss the scientific reasons for CMB observation, we present a detailed explanation of how QUBIC will use bolometric interferometry to measure CMB polarization and in particular we discuss the author's contribution to the project. As part of the sub-mm optics research group in the National University of Ireland Maynooth the author was charged with the design and modeling of the optics that would focus the beam from the sky onto the bolometric detectors. This thesis describes various types of re ecting and refracting optics that were investigated. The results we present are useful not only for the QUBIC instrument, but for the design of imaging experiments in general. Detection of CMB B-mode polarization is one of the supreme goals of modern cosmology. The faintness of this signal, combined with the interferometric observing technique, places extreme performance specifications on the QUBIC optics. Fortunately, as we shall show, there are types of well-known re ecting and refracting telescopes that are suitable for QUBIC. In this thesis I propose a design for the quasi-optical combiner that will perform as required