Šiame darbe pristatysime du alternatyvius, vienus iš pačių populiariausių, realaus laiko šešėlių generavimo metodus. Tai šešėlių planų (angl. shadow maps) ir šešėlių tūrių (angl. shadow volumes) metodai. Kadangi šie metodai turi įvairių skirtingų privalumų ir trūkumų, yra nuolat tobulinami, kartais kuriami ir iš jų ir hibridiniai algoritmai, kurie perimtų kuo daugiau šių dviejų technikų gerųjų savybių. Todėl šiame darbe pamėginsime nustatyti ir įvertinti, kuriais atvejais yra vienas geresnis už kitą. / In this work we introduce to two alternative, most popular real time shadow rendering techniques. This is shadow map (or mapping) and shadow volumes techniques. Because those two methods have diferent advantages and weaknesses, there are always in development, and sometimes hybrid algorithms are created, which would absorb more good features from them. So in this work we tried to determine and rate in which cases one is better than another.

Skuggor är centrala för hur människan uppfattar världen. Inom datorspel och andra interaktiva 3D-applikationer är det viktigt att underlätta förståelsen av scenen och det finns även ofta en stark vilja att skapa realistiska miljöer. Detta samt att skuggsättning är en komplicerad och prestandakrävande operation gör det till ett viktigt område inom realtidsgrafik. Vi undersöker i denna avhandling relationen mellan prestandan (renderingstiden) för de två populära metoderna för skuggsättning inom realtidsgrafik, shadow mapping och shadow volumes. Undersökningen avgränsas till två utvalda varianter av de ursprungliga algoritmerna. I och med lanseringen av den nya versionen av Direct3D, version 10, öppnas möjligheten för optimeringar av algoritmerna genom användandet av framförallt geometry shaders. På grund av detta implementerar vi algoritmerna både med och utan den nya funktionalitet som introduceras i Direct3D 10 för att besvara om det är möjligt att förbättra prestandan för algoritmerna i Direct3D 10. Resultatet visar tydligt shadow mapping-algoritmens överlägsenhet för annat än scener med mycket få polygoner. Variabler så som ljusets infallsvinkel och objekts storlek har liten inverkan på det slutgiltiga resultatet för när vilken algoritm har bättre prestanda. Resultatet visar även tydligt att användandet av geometry shaders ger en mycket kraftig försämring av prestandan för båda algoritmerna. / Inom interaktiv 3D-grafik som exempelvis datorspel är det viktigt att skapa realistiska miljöer. Att rita ut en realistisk 3D-värld såpass snabbt att användaren inte kan se enskilda bildrutor kräver mycket kraft av datorn. Det är därför viktigt att datorprogrammet använder snabba och effektiva algoritmer. Skuggor är viktigt för att skapa realistiska 3D-miljöer. Detta arbete jämför snabbheten och effektiviteten mellan två olika metoder för att bestämma vad i 3D-världen som ligger i skugga.

This master's project focuses on basic techniques of creating shadows in 3D computer graphics. Two basic techniques are compared. Those are shadow maps and shadow volumes. Another technique combining previouse two is proposed.

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.

Background. Shadow mapping is a method that is used for generating and imitating shadows in 3D-spaces. This technique has been used in the entertainment media industry in the form of games, movies and 3D renderings of environments to create a more realistic experience for consumers. Shadow mapping is not a perfect technique, and is performance costing on the GPU; however, some methods save performance by reducing the complexity of geometrical shapes and textures depending on the distance between observer and object. These techniques are based on that the observer will not notice the complexity reductions; can the usage of such methods be extended to textures covered in shadows without any consequences in the aspect of visual appearance and preference? Objectives. This thesis aims to examine if there is a possibility to extend the usage of LOD techniques to shadowed textures and to analyze individuals’ preferences of texture variants that are covered in shadows. Additionally, proposing the method of lowering texture resolution by using DirectX:s sampler data type, which is configurable to increase the level of details with mipmapping when sampling textures. Methods. This document presents a user study using the Two-alternative forced choice method and PsychoPy application to create a visual test. The visual test was conducted in a controlled and observed environment with volunteering participants. The objective of the visual test was to go through several sets of different images, and to choose which image of each set that was preferred. The stimulus was repeated with the initial images fading in and out slowly to prevent carry over effects. After the test participants were asked to fill out a questionnaire. The questionnaire assessed if they noticed any differences within the shadows, and if they had any additional thoughts about the experiment. Results. The results from the study were then evaluated through a binomial test that yielded that there was no statistically significant difference in preference between the lowered texture resolution in shadows and normal texture resolution in shadows. Separately evaluating the environments showed that there was a preference for shadowed low-resolution textures in environments that were dark. The environments with high illumination had more varied results. There were 17 participants that volunteered in the test and were ranging from the ages 18 to 29. Conclusions. With the results presented it was shown that the shadowed lowresolution textures were preferred in environments with low illumination. This suggests that the proposed concept method is better suited for similar environments. However, several factors may have affected the results. Factors such as images being too dark, the lack of exaggerated images, images fading in and out too fast, few participants, more partaking will assure there is less chance for bias.

Virtual crowd rendering have been used in film industry with offine rendering methods for a long time. But its existence in interactive real-time applications such as video games is not so common due to the limited rendering power of current graphics hardware. This thesis describes a novel method to improve shadow mapping performance of a crowded scene by taking into account the screen space visibility of the casted shadow of a crowd instance when rendering the shadow maps. A grid-based visibility mask creation method is proposed which is irrelevant to scene complexity. This improves the rendering performance especially when there are many occluded instances of the crowd which is a common scenario in urban environments and accelerates the usage of crowds in real time applications, such as games. We compute visibility of all agents in a crowd in parallel on the graphics processing unit(GPU) without having a requirement of a stencil buer or light direction dependent shadow mask. Technique also improves the view space rendering time by reducing the visibility check cost of the agents that are located on the invisible areas of the scene. The methodology introduced in this thesis gets more effective in each shadow map rendering pass by re-using the same visibility mask for shadow caster culling and enables many local lights with shadows. We also give a brief information about the state of the art of crowd rendering and shadowing, explaining how suitable the method with the implementations of different shadow mapping approaches. The technique is very well compatible with the modern crowd rendering techniques such as skinned instancing, dynamic level of detail(LOD) determination and GPU-based simulation.

Shadows have captivated humanity since the dawn of time; with the current age being no exception – shadows are core to realism and ambience, be it to invoke a classic Baroque interplay of lights, darks and colours as the case in Rembrandt van Rijn’s Militia Company of Captain Frans Banning Cocq or to create a sense of mystery as found in film noir and expressionist cinematography. Shadows, in this traditional sense, are regions of blocked light – the combined effect of placing an object between a light source and surface. This dissertation focuses on real-time shadow generation as a subset of 3D computer graphics. Its main focus is the critical analysis of numerous real-time shadow rendering algorithms and the construction of an empirically derived system for the high-speed rendering of shadows. This critical analysis allows us to assess the relationship between shadow rendering quality and performance. It also allows for the isolation of key algorithmic weaknesses and possible bottleneck areas. Focusing on these bottleneck areas, we investigate several possibilities of improving the performance and quality of shadow rendering; both on a hardware and software level. Primary performance benefits are seen through effective culling, clipping, the use of hardware extensions and by managing the polygonal complexity and silhouette detection of shadow casting meshes. Additional performance gains are achieved by combining the depth-fail stencil shadow volume algorithm with dynamic spatial subdivision. Using this performance data gathered during the analysis of various shadow rendering algorithms, we are able to define a fuzzy logic-based expert system to control the real-time selection of shadow rendering algorithms based on environmental conditions. This system ensures the following: nearby shadows are always of high-quality, distant shadows are, under certain conditions, rendered at a lower quality and the frames per second rendering performance is always maximised. / Dissertation (MSc)--University of Pretoria, 2009. / Computer Science / unrestricted

This thesis is focused on describing methods of computation of global illumination of 3D graphics scenes in real-time. First chapter contains brief introduction to the issue of global illumination (GI) computation, as well as quick summarisation of principles of most commonly used GI computation approaches. A method of visibility computing for indirect illumination, taking advantage of Imperfect Shadow Mapping, is introduced next. After closer examination of this method and prerequisite algorithms follows a description of its practical implementation, as well as of the structure of simple demonstrative application. Next chapter then contains testing and brief examination and evaluation of resulting program's behaviour. Finally, a possible method extension by means of virtual point light clustering is proposed.

[pt] O mapeamento de sombras é uma técnica de renderização amplamente utilizada para a geração de sombras de superfícies arbitrárias em tempo real. No entanto, devido a sua natureza amostrada, apresenta dois problemas de difícil resolução: o aspecto chamuscado de objetos e a aparência serrilhada das bordas das sombras. Em particular, o sombreamento de modelos CAD (Computer-Aided Design) apresenta desafios ainda maiores, devido à existência de objetos estreitos com silhuetas complexas e o elevado grau de complexidade em profundidade. Neste trabalho, fazemos uma análise detalhada dos problemas de chamuscamento e serrilhamento, revisando e completando trabalhos de diferentes autores. Apresentamos ainda algumas propostas para melhoria de algoritmos existentes: o alinhamento de amostras independente de programas de vértice, um parâmetro generalizado para o LiSPSM (Light- Space Perspective Shadow Map), e um esquema de particionamento adaptativo em profundidade. Em seguida, investigamos a eficácia de diferentes algoritmos quando aplicados a modelos CAD, avaliando-os em critérios como facilidade de implementação, qualidade visual e eficiência computacional. / [en] Shadow mapping is a widely used rendering technique for shadow generation on arbitrary surfaces. However, because of the limited resolution available for sampling the scene, the algorithm presents two difficult problems to be solved: the incorrect self-shadowing of objects and the jagged appearance of shadow borders, also known as aliasing. Generating shadows for CAD (Computer-Aided Design) models presents additional challenges, due to the existence of many thin complex-silhouette objects and the high depth complexity. In this work, we present a detailed analysis of self-shadowing and aliasing by reviewing and building on works from different authors. We also propose some impromevents to existing algorithms: sample alignment without vertex shaders, a generalized parameter for the LiSPSM (Light-Space Perspective Shadow Map) algorithm, and an adaptive z- partitioning scheme. Finally, we investigate the effectiveness of different algorithms when applied to CAD models, considering ease of implementation, visual quality and computational efficiency.

Focus of this master's thesis is a study of modern techniques in computer graphics and designing and developing custom application based on which could be developed new game engine. In this thesis are highlighted techniques for creating large terrains, advanced shadows, physically based sky rendering and drawing large set of objects. Finally, performance testing of these modules is performed.