Дисертації з теми "Physically based rendering (PBR)"

Актуальність теми. Актуальною задачею комп’ютерної графіки являється отримання реалістичних зображень, котрі активно користуються попитом в промисловості, ігровій індустрії та кіно. Фотореалістичне зображення характеризується такими ефектами, як м’які тіні, напівтіні, каустика, динамічне розмиття, глибина різкості, нечіткі відбиття, блиск, напівпрозорість. Серед існуючих підходів фотореалістичної візуалізації методи трасування променів являються найбільш точними, оскільки вони базуються на фізичній моделі поширення світла. Існує багатий спектр різноманітних методів трасування променів, отже з’являється необхідність у вибірці найбільш ефективних точних методів трасування променів, котрі будуть в середній мірі коректно працювати для широкого ряду статичних (в майбутньому і динамічних) сцен, що проходять візуалізацію. Об’єктом дослідження є процес фізично обґрунтованого рендерингу і процес трасування променів. Предметом дослідження є способи трасування променів та методи розрахунку індексу передачі кольору. Мета роботи: дослідження методів PBR (Physical Based Rendering), їх одночасного використання для отримання максимального ефекту реалізму; оцінка здатності джерела світла виявляти всі частоти його кольорового спектру у порівнянні з контрольним світлом. Наукова новизна, а точніше – інноваційне рішення полягає в тому, що розроблений рушій реалізує обчислення індексу передачі кольору (CRI - Color Rendering Index) з високим рівнем точності відносно очікуваних значень контрольних джерел світла. Практична цінність проведених досліджень полягає у розробці нового PBRE, який для рендерингу сцен використовує емпіричні моделі освітлення; реалізовані такі моделі BRDF, як Ламберта, Орена Найара, Торренса Спарроу, дзеркального відбиття, дзеркального пропускання і виміряного BRDF. Реалізована підтримка декількох технік трасування променів: трасування Уайтеда і трасування шляху. Розраховуються кольори з використанням спектральних даних і колірний простір CIE XYZ в сценах PBR для досягнення високої передачі кольору. TTFD також підтримує обчислення індексу передачі кольору (CRI – Color Rendering Index). Цей показник описує здатність джерела світла точно відображати всі частоти його колірного спектра в порівнянні з ідеальним еталонним світлом аналогічного типу. Структура та обсяг роботи. Магістерський дипломний проект складається зі вступу, чотирьох розділів та висновків. У вступі подано загальну характеристику роботи, зроблено оцінку сучасного стану проблеми, обґрунтовано актуальність напрямку досліджень, сформульовано мету і задачі досліджень, показано наукову новизну отриманих результатів і практичну цінність роботи. У першому розділі розглянуто принципи колориметрії та радіометрії. Вони складають основу деяких основних ключових особливостей TTFD. Зокрема, розрахунок кольору і методи освітлення / затінення, реалізовані в TTFD, використовують поняття, представлені даному розділі. У другому розділі розглянуто трасування променів: фотореалістичний рендеринг (візуалізація). Коротка класифікація алгоритмів трасування променів. Вирішення рівняння рендеринга. У третьому розділі наведено особливості реалізації розробленої системи. У четвертому розділі представлено підходи до тестування системи в цілому та окремих модулів. У висновках представлені результати проведеної роботи. Робота представлена на 116 аркушах, містить посилання на список використаних літературних джерел. Ключові слова: фізичний рендеринг (PBR), трасування променів, індекс передачі кольору, емпіричні моделі освітлення, модель Уайтеда, трасування шляху.
Relevance of the topic. The actual task of computer graphics is to obtain realistic images that are actively in demand in industry, gaming and film industry. A photorealistic image is characterized by such effects as soft shadows, partial shade, caustic, dynamic blur, depth of field, fuzzy reflection, shine, translucency. Among the existing approaches of photorealistic visualization, ray tracing methods are the most accurate because they are based on a physical model of light propagation. There is a wide range of different ray-tracing methods, and therefore there is a need to select the most efficient, accurate ray-tracing methods that will, in average, work correctly for a wide range of static (future dynamic) scenes, and are being visualized. The object of the research is the process of physically sound rendering and the ray tracing process. The subject of research is the methods of ray tracing and methods for calculating the color rendering index. Objective: to study the methods of PBR (Physical Based Rendering), their simultaneous use to obtain the maximum effect of realism; assessment of the ability of a light source to detect all the frequencies of its color spectrum compared to the control light. The scientific novelty, or rather, an innovative solution, is that the engine developed implements the calculations of the color rendering index (CRI - Color Rendering Index) with a high degree of accuracy relative to the expected values of the control light sources. The practical value of the research is the development of a new PBRE, which employs empirical lighting models for rendering scenes; BRDF models such as Lambert, Oren Nayar, Torrens Sparrow, specular reflection, specular transmission and measured BRDF are implemented. Implemented support for several ray tracing techniques: Traced by Wyted and path tracing. Colors are calculated using spectral data and CIE XYZ color space in PBR scenes to achieve high color rendering. TTFD also supports Color Rendering Index (CRI) calculations. This indicator describes the ability of a light source to accurately reflect all the frequencies of its color spectrum compared to ideal reference light of a similar type. Structure and scope of work. Master thesis project consists of introduction, four chapters and conclusions. The introduction presents a general description of the work, assesses the current state of the problem, substantiates the relevance of the research area, formulates the goals and objectives of the research, shows the scientific novelty of the results and practical value of the work. The first section discusses the principles of colorimetry and radiometry. They form the basis of some key TTFD key features. In particular, color calculations and lighting / shading methods implemented in TTFD use the concept presented in this section. The second section deals with ray tracing: photorealistic rendering (visualization). Brief classification of ray tracing algorithms. Solution of the rendering equation. The third section presents the features of the implementation of the developed system. The fourth section presents approaches to testing the system as a whole and individual modules. The findings present the results of this work. The work is presented on 116 pages, contains links to the list of references used.
Актуальность темы. Актуальной задачей компьютерной графики является получение реалистичных изображений, которые активно пользуются спросом в промышленности, игровой индустрии и кино. Фотореалистичное изображение характеризуется такими эффектами, как мягкие тени, полутени, каустика, динамическое размытие, глубина резкости, нечеткие отражение, блеск, полупрозрачность. Среди существующих подходов фотореалистичной визуализации методы трассировки лучей являются наиболее точными, поскольку они базируются на физической модели распространения света. Существует богатый спектр различных методов трассировки лучей, следовательно появляется необходимость в выборке наиболее эффективных точных методов трассировки лучей, которые будут в средней степени правильно работать для широкого ряда статических (в будущем и динамических) сцен, проходят визуализацию. Объектом исследования является процесс физически обоснованного рендеринга и процесс трассировки лучей. Предметом исследования являются способы трассировки лучей и методы расчета индекса цветопередачи. Цель работы: исследование методов PBR (Physical Based Rendering), их одновременного использования для получения максимального эффекта реализма; оценка способности источника света выявлять все частоты его цветового спектра по сравнению с контрольным светом. Научная новизна, а точнее - инновационное решение, заключается в том, что разработан двигатель реализует вычисления индекса цветопередачи (CRI - Color Rendering Index) с высокой степенью точности относительно ожидаемых значений контрольных источников света. Практическая ценность проведенных исследований состоит в разработке нового PBRE, который для рендеринга сцен использует эмпирические модели освещения; реализованы такие модели BRDF, как Ламберта, Орена Найара, Торренса Спарроу, зеркального отражения, зеркального пропускания и измеренного BRDF. Реализована поддержка нескольких техник трассировки лучей: трассировки Уайтеда и трассировки пути. Рассчитываются цвета с использованием спектральных данных и цветовое пространство CIE XYZ в сценах PBR для достижения высокой цветопередачи. TTFD также поддерживает вычисления индекса цветопередачи (CRI - Color Rendering Index). Этот показатель описывает способность источника света точно отражать все частоты его цветового спектра по сравнению с идеальным эталонным светом аналогичного типа. Структура и объем работы. Магистерский дипломный проект состоит из введения, четырех глав и выводов. Во введении представлена общая характеристика работы, произведена оценка современного состояния проблемы, обоснована актуальность направления исследований, сформулированы цели и задачи исследований, показано научную новизну полученных результатов и практическую ценность работы. В первом разделе рассмотрены принципы колориметрии и радиометрии. Они составляют основу некоторых основных ключевых особенностей TTFD. В частности, расчет цвета и методы освещения / затенения, реализованные в TTFD, используют понятие, представленные данном разделе. Во втором разделе рассмотрены трассировки лучей: фотореалистичный рендеринг (визуализация). Краткая классификация алгоритмов трассировки лучей. Решение уравнения рендеринга. В третьем разделе приведены особенности реализации разработанной системы. В четвертом разделе представлены подходы к тестированию системы в целом и отдельных модулей. В выводах представлены результаты проведенной работы. Работа представлена на 116 листах, содержит ссылки на список использованных литературных источников.

Physically Based Rendering (PBR) is a mainstay of offline and real-time rendering. The principles behind it were first implemented in offline renderers due to processing time not being an issue. Subsequently, real-time rendering began using the same principles especially in the medium of games. Transferring the methods to a real-time environment has led to increasing number of compromises in the physicality, but the principles remain the same. Some of the main goals include adherence to empirically measured reflectances that, among other issues, conserve light energy realistically. With industries such as automotive manufacturers wanting to incorporate modern rendering techniques to their products, there is a need to investigate how such techniques perform in low-end devices. This thesis tests PBR in different devices, from low-end to high-end, to determine the specific performance impacts of PBR. The implementation of PBR presented in this thesis is portable to different hardware platforms and provides approximately the same results in each device. PBR, as it is implemented in modern game engines, impacts the performance significantly. However, there are methodology components that can be applied to rendering pipelines with minimal cost
Fysiikkaperusteinen renderöinti (PBR) on offline- ja reaaliaikaisen renderöinnin tärkeä osa. Sen takana olevat periaatteet otettiin ensin käyttöön offline-renderöinnissä eli elokuvagrafiikassa, koska siinä käsittelyaika ei ole ongelma. Reaaliaikaisessa renderöinnissä, etenkin peleissä, on alettu käyttämään samoja periaatteita. Menetelmien siirtäminen reaaliaikaiseen ympäristöön on lisännyt fyysisyyteen liittyviä kompromisseja, mutta periaatteet ovat pysyneet samoina. Päätavoitteena PBR:ssä on valon heijastumisen empiirisesti mitattujen seurauksien noudattaminen. Yksi tälläinen seuraus on muun muassa valon energian säilyvyys. Teollisuudenaloilla, kuten autoteollisuudessa, valmistajat haluavat sisällyttää tuotteisiinsa nykyaikaista renderöintitekniikkaa. Tämä luo tarpeen selvittää, miten tällaiset tekniikat toimivat resurssiköyhissä laitteissa. Tämä diplomityö testaa PBR:n toteutusta eri laitteissa, pienitehoisesta suurempitehoiseen, PBR:lle erityisien suorituskykyvaikutusten määrittämiseksi. Tässä diplomityössä esitettävä, testaukseen tarkoitettu, PBR:n toteutus on siirrettävissä eri laitteistoalustoille ja se tuottaa suunnilleen samat visuaaliset tulokset kussakin laitteessa. PBR, joka on toteutettu samalla tavalla kuin nykyaikaisissa pelimoottoreissa, vaikuttaa suorituskykyyn merkittävästi sulautetuissa järjestelmissä. PBR sisältää kuitenkin komponentteja, joita voidaan käyttää renderöintiin ilman suuria tehovaatimuksia

Lighting is essential to generate realistic images using computer graphics. The computation of lighting takes into account the multitude of ways which light propagates around a virtual scene. This is termed global illumination, and is a vital part of physically-based rendering. Although providing compelling and accurate images, this is a computationally expensive process. This thesis presents several methods to improve the speed of global illumination computation, and therefore enables faster image synthesis. Global illumination can be calculated in an offline process, typically taking many minutes to hours to compute an accurate solution, or it can be approximated at interactive or real-time rates. This work proposes three methods which tackle the problem of improving the efficiency of computing global illumination. The first is an interactive method for calculating multiple-bounce global illumination on graphics hardware, which exploits the power of the graphics pipeline to create a voxelised representation of the scene through which light transport is computed. The second is an unbiased physically-based algorithm for improving the efficiency of path generation when calculating global illumination in complicated scenes. This is adaptive, and learns information about the lighting in the scene as the rendering progresses, and uses this to reduce variance in the image. In both common scenes used in graphics and situations which involve difficult light paths, this method gives a 30 - 70% boost in performance. The third method in this thesis is a sampling method which improves the efficiency of the common indoor-outdoor lighting scenario. This is done by both combining the lighting distribution with view importance, and automatically determining the important areas of the scene in which to start light paths. This gives a speed up of between three times, and two orders of magnitude, depending on scene and lighting complexity.

Le rendu fondé sur la physique est utilisé pour le design, l'illustration ou l'animation par ordinateur. Ce type de rendu produit des images photo-réalistes en résolvant les équations qui décrivent le transport de la lumière dans une scène. Bien que ces équations soient connues depuis longtemps, et qu'un grand nombre d'algorithmes aient été développés pour les résoudre, il n'en existe pas qui puisse gérer de manière efficace toutes les scènes possibles. Plutôt qu'essayer de développer un nouvel algorithme de simulation d'éclairage, nous proposons d'améliorer la robustesse de la plupart des méthodes utilisées à ce jour et/ou qui sont amenées à être développées dans les années à venir. Nous faisons cela en commençant par identifier les sources de non-robustesse dans un moteur de rendu basé sur la physique, puis en développant des méthodes permettant de minimiser leur impact. Le résultat de ce travail est un ensemble de méthodes utilisant différents outils mathématiques et algorithmiques, chacune de ces méthodes visant à améliorer une partie spécifique d'un moteur de rendu. Nous examinons aussi comment les architectures matérielles actuelles peuvent être utilisées à leur maximum afin d'obtenir des algorithmes plus rapides, sans ajouter d'approximations. Bien que les contributions présentées dans cette thèse aient vocation à être combinées, chacune d'entre elles peut être utilisée seule : elles sont techniquement indépendantes les unes des autres
Physically-based rendering is used for design, illustration or computer animation. It consists in producing photorealistic images by solving the equations which describe how light travels in a scene. Although these equations have been known for a long time and many algorithms for light simulation have been developed, no algorithm exists to solve them efficiently for any scene. Instead of trying to develop a new algorithm devoted to light simulation, we propose to enhance the robustness of most methods used nowadays and/or which can be developed in the years to come. We do this by first identifying the sources of non-robustness in a physically-based rendering engine, and then addressing them by specific algorithms. The result is a set of methods based on different mathematical or algorithmic methods, each aiming at improving a different part of a rendering engine. We also investigate how the current hardware architectures can be used at their maximum to produce more efficient algorithms, without adding approximations. Although the contributions presented in this dissertation are meant to be combined, each of them can be used in a standalone way: they have been designed to be internally independent of each other

In this paper, I present a framework for implementing level of detail (LOD) for a 3d physically based fire rendering running on the GPU. While realistic fire rendering that runs in real time exists, it is generally not used in real-time applications such as game, due to the high cost of running such a rendering. Most research into the rendering of fire is only concerned with the fire itself, and not how it can best be included in larger scenes with a multitude of other complex objects. I present methods for increasing the efficiency of a physically based fire rendering without harming its visual quality, by dynamically adjusting the detail level of the fire according to its importance for the current view. I adapt and use methods created both for LOD and for other areas to alter the detail level of the visualization and simulation of a fire rendering. The desired detail level is calculated by evaluating certain conditions such as visibility and distance from the viewpoint, and then used to adjust the detail level of the visualization and simulation of the fire. The implementation of the framework could not be completed in time, but a number of tests were run to determine the effect of the different methods used. These results indicate that by making adjustments to the simulation and visualization of the fire, large boosts in performance are gained without significantly harming the visual quality of the fire rendering.

This thesis presents methods for photorealistic rendering of virtual objects so that they can be seamlessly composited into images of the real world. To generate predictable and consistent results, we study physically based methods, which simulate how light propagates in a mathematical model of the augmented scene. This computationally challenging problem demands both efficient and accurate simulation of the light transport in the scene, as well as detailed modeling of the geometries, illumination conditions, and material properties. In this thesis, we discuss and formulate the challenges inherent in these steps and present several methods to make the process more efficient. In particular, the material contained in this thesis addresses four closely related areas: HDR imaging, IBL, reflectance modeling, and efficient rendering. The thesis presents a new, statistically motivated algorithm for HDR reconstruction from raw camera data combining demosaicing, denoising, and HDR fusion in a single processing operation. The thesis also presents practical and robust methods for rendering with spatially and temporally varying illumination conditions captured using omnidirectional HDR video. Furthermore, two new parametric BRDF models are proposed for surfaces exhibiting wide angle gloss. Finally, the thesis also presents a physically based light transport algorithm based on Markov Chain Monte Carlo methods that allows approximations to be used in place of exact quantities, while still converging to the exact result. As illustrated in the thesis, the proposed algorithm enables efficient rendering of scenes with glossy transfer and heterogenous participating media.
En av de största utmaningarna inom datorgrafik är att syntetisera, eller rendera, fotorealistiska bilder. Fotorealistisk rendering används idag inom många tillämpningsområden såsom specialeffekter i film, datorspel, produktvisualisering och virtuell verklighet. I många praktiska tillämpningar av fotorealistisk rendering är det viktigt att kunna placera in virtuella objekt i fotografier, så att de virtuella objekten ser verkliga ut. IKEA-katalogen, till exempel, produceras i många olika versioner för att passa olika länder och regioner. Grunden till de flesta bilderna i katalogen är oftast densamma, men symboler och standardmått på möbler varierar ofta för olika versioner av katalogen. Istället för att fotografera varje version separat kan man använda ett grundfotografi och lägga in olika virtuella objekt såsom möbler i fotot. Genom att på det här sättet möblera ett rum virtuellt, istället för på riktigt, kan man också snabbt testa olika möbleringar och därmed göra ekonomiska besparingar. Den här avhandlingen bidrar med metoder och algoritmer för att rendera fotorealistiska bilder av virtuella objekt som kan blandas med verkliga fotografier. För att rendera sådana bilder används fysikaliskt baserade simuleringar av hur ljus interagerar med virtuella och verkliga objekt i motivet. För fotorealistiska resultat kräver simuleringarna noggrann modellering av objektens geometri, belysning och materialegenskaper, såsom färg, textur och reflektans. För att de virtuella objekten ska se verkliga ut är det viktigt att belysa dem med samma ljus som de skulle ha haft om de var en del av den verkliga miljön. Därför är det viktigt att noggrant mäta och modellera ljusförhållanden på de platser i scenen där de virtuella objekten ska placeras. För detta använder vi High Dynamic Range-fotografi, eller HDR. Med hjälp av HDR-fotografi kan vi noggrant mäta hela omfånget av det infallande ljuset i en punkt, från mörka skuggor till direkta ljuskällor. Detta är inte möjligt med traditionella digitalkameror, då det dynamiska omfånget hos vanliga kamerasensorer är begränsat. Avhandlingen beskriver nya metoder för att rekonstruera HDR-bilder som ger mindre brus och artefakter än tidigare metoder. Vi presenterar också metoder för att rendera virtuella objekt som rör sig mellan regioner med olika belysning, eller där belysningen varierar i tiden. Metoder för att representera spatiellt varierande belysning på ett kompakt sätt presenteras också. För att noggrant beskriva hur glansiga ytor sprider eller reflekterar ljus, beskrivs också två nya parametriska modeller som är mer verklighetstrogna än tidigare reflektionsmodeller. I avhandlingen presenteras också en ny metod för effektiv rendering av motiv som är mycket beräkningskrävande, till exempel scener med uppmätta belysningsförhållanden, komplicerade  material, och volumetriska modeller som rök, moln, textiler, biologisk vävnad och vätskor. Metoden bygger på en typ av så kallade Markov Chain Monte Carlo metoder för att simulera ljustransporten i scenen, och är inspirerad av nyligen presenterade resultat inom matematisk statistik. Metoderna som beskrivs i avhandlingen presenteras i kontexten av fotorealistisk rendering av virtuella objekt i riktiga miljöer, då majoriteten av forskningen utförts inom detta område. Flera av de metoder som presenteras i denna avhandling är dock tillämpbara inom andra domäner, såsom fysiksimulering, datorseende och vetenskaplig visualisering.

In this physically-based tornado simulation, the tornado-scale approach techniques are applied to simulate the tornado formation environment. The three-dimensional Navier-Stokes equations for incompressible viscous fluid flows are used to model the tornado dynamics. The boundary conditions applied in this simulation lead to rotating and uplifting flow movement as found in real tornadoes and tornado research literatures. Moreover, a particle system is incorporated with the model equation solutions to model the irregular tornado shapes. Also, together with appropriate boundary conditions, varied particle control schemes produce tornadoes with different shapes. Furthermore, a modified metaball scheme is used to smooth the density distribution. Texture mapping, antialising, animation and volume rendering are applied to produce realistic visual results. The rendering algorithm is implemented in OpenGL.

Background The increase in screen resolution has increased from HD to Ultra-HDduring the last decade. A modern game today with Ultra-HD resolution has overeight million pixels that need to be shaded, combined with the expensive shadingmethod Physically Based Rendering the equations needed to calculate each pixel arenumerous. Objectives This the study aims to remove complexity from the Physically BasedRendering shading method in the form of roughness in low-lit areas. The low-lit areaswill instead be rendered without the roughness attribute. By removing roughnessless calculations will be performed. Methods To remove roughness from low-lit areas the light had to be approximatedusing a diffuse model. The pixel was later converted via Hue Saturation PerceivedBrightness to calculate the brightness. If the pixel was under the given threshold,the pixel was shaded using a low-complexity Physically Based Rendering implemen-tation without roughness. A user study was conducted using Unity game enginewith eight participants being asked to compare different stimuli all rendered withdifferent thresholds for darkness with a reference picture. The aim of the study wasto ascertain if the stimuli without roughness had any perceivable difference from thereference. Results The results of the study show the majority of the participants noticinga difference when comparing the stimuli with the reference. The areas affected wasnot only the low-lit areas but the whole scene. The energy conversion without theroughness value made the whole scene appear darker. Conclusions The roughness value is an integral part of energy conversion andwithout it, the scene will appear much darker. While the majority of participantsnoticed a difference, the lowest threshold resembled the original the most

Lorsque l'on affiche un objet 3D sur un écran d'ordinateur, on transforme cet objet en une image, c.a.d en un ensemble de pixels colorés. On appelle Rendu la discipline qui consiste à trouver la couleur à associer à ces pixels. Calculer la couleur d'un pixel revient à intégrer la quantité de lumière arrivant de toutes les directions que la surface renvoie dans la direction du plan image, le tout pondéré par une fonction binaire déterminant si un point est visible ou non. Malheureusement, l'ordinateur ne sait pas calculer des intégrales on a donc deux méthodes possibles : Trouver une expression analytique qui permet de supprimer l'intégrale de l'équation (approche basée statistique). Approximer numériquement l'équation en tirant des échantillons aléatoires dans le domaine d'intégration et en en déduisant la valeur de l'intégrale via des méthodes dites de Monte Carlo. Nous nous sommes ici intéressés à l'intégration numérique et à la théorie de l'échantillonnage. L'échantillonnage est au cœur des problématiques d'intégration numérique. En informatique graphique, il est capital qu'un échantillonneur génère des points uniformément dans le domaine d’échantillonnage pour garantir que l'intégration ne sera pas biaisée. Il faut également que le groupe de points généré ne présente aucune régularité structurelle visible, au risque de voir apparaître des artefacts dit d'aliassage dans l'image résultante. De plus, les groupes de points générés doivent minimiser la variance lors de l'intégration pour converger au plus vite vers le résultat. Il existe de nombreux types d'échantillonneurs que nous classeront ici grossièrement en 2 grandes familles : Les échantillonneurs bruit bleu, qui ont une faible la variance lors de l'intégration tout en générant de groupes de points non structurés. Le défaut de ces échantillonneurs est qu'ils sont extrêmement lents pour générer les points. Les échantillonneurs basse discrépance, qui minimisent la variance lors de l'intégration, génèrent des points extrêmement vite, mais qui présentent une forte structure, générant énormément d'aliassage. Notre travail a été de développer des échantillonneurs hybrides, combinant à la fois bruit bleu et basse discrépance
When you display a 3D object on a computer screen, we transform this 3D scene into a 2D image, which is a set of organized colored pixels. We call Rendering all the process that aims at finding the correct color to give those pixels. This is done by integrating all the light rays coming for every directions that the object's surface reflects back to the pixel, the whole being ponderated by a visibility function. Unfortunately, a computer can not compute an integrand. We therefore have two possibilities to solve this issue: We find an analytical expression to remove the integrand (statistic based strategy). Numerically approximate the equation by taking random samples in the integration domain and approximating the integrand value using Monte Carlo methods. Here we focused on numerical integration and sampling theory. Sampling is a fundamental part of numerical integration. A good sampler should generate points that cover the domain uniformly to prevent bias in the integration and, when used in Computer Graphics, the point set should not present any visible structure, otherwise this structure will appear as artifacts in the resulting image. Furthermore, a stochastic sampler should minimize the variance in integration to converge to a correct approximation using as few samples as possible. There exists many different samplers that we will regroup into two families: Blue Noise samplers, that have a low integration variance while generating unstructured point sets. The issue with those samplers is that they are often slow to generate a pointset. Low Discrepancy samplers, that minimize the variance in integration and are able to generate and enrich a point set very quickly. However, they present a lot of structural artifacts when used in Rendering. Our work aimed at developing hybriod samplers, that are both Blue Noise and Low Discrepancy

Outlined is a new approach to the problem of surfacing particle-based fluid simulations. The key idea is to construct a surface that is as smooth as possible while remaining faithful to the particle locations. We describe a mesh-based algorithm that expresses the surface in terms of a constrained optimization problem. Our algorithm incorporates a secondary contribution in Marching Tiles, a generalization of the Marching Cubes isosurfacing algorithm. Marching Tiles provides guarantees on the minimum vertex valence, making the surface mesh more amenable to numerical operators such as the Bilaplacian.

With the rapidly growing computational power of modern computers, physically based rendering has found its way into real world applications. Real-time simulations and renderings of fire and smoke had become one major research interest in modern video game industry, and will continue being one important research direction in computer graphics. To visually recreate realistic dynamic fire and smoke is a complicated problem. Furthermore, to solve the problem requires knowledge from various areas, ranged from computer graphics and image processing to computational physics and chemistry. Even though most of the areas are well-studied separately, when combined, new challenges will emerge. This thesis focuses on three aspects of the problem, dynamic, real-time and realism, to propose a solution in form of a GPGPU pipeline, along with its implementation. Three main areas with application in the problem are discussed in detail: fluid simulation, volumetric radiance estimation and volumetric rendering. The weights are laid upon the first two areas. The results are evaluated around the three aspects, with graphical demonstrations and performance measurements. Uniform grids are used with Finite Difference (FD) discretization scheme to simplify the computation. FD schemes are easy to implement in parallel, especially with ComputeShader, which is well supported in Unity engine. The whole implementation can easily be integrated into any real-world applications in Unity or other game engines that support DirectX 11 or higher.

Despite the notable progress in physically-based rendering, there is still a long way to go before we can automatically generate predictable images of biological materials. In this thesis, we address an open problem in this area, namely the spectral simulation of light interaction with human skin, and propose a novel biophysically-based model that accounts for all components of light propagation in skin tissues, namely surface reflectance, subsurface reflectance and transmittance, and the biological mechanisms of light absorption by pigments in these tissues. The model is controlled by biologically meaningful parameters, and its formulation, based on standard Monte Carlo techniques, enables its straightforward incorporation into realistic image synthesis frameworks. Besides its biophysicallybased nature, the key difference between the proposed model and the existing skin models is its comprehensiveness, i. e. , it computes both spectral (reflectance and transmittance) and scattering (bidirectional surface-scattering distribution function) quantities for skin specimens. In order to assess the predictability of our simulations, we evaluate their accuracy by comparing results from the model with actual skin measured data. We also present computer generated images to illustrate the flexibility of the proposed model with respect to variations in the biological input data, and its applicability not only in the predictive image synthesis of different skin tones, but also in the spectral simulation of medical conditions.

Made available in DSpace on 2014-06-12T15:57:17Z (GMT). No. of bitstreams: 2 arquivo3157_1.pdf: 3737373 bytes, checksum: 7ca491f9a72f2e9cf51764a7acac3e3c (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Esta dissertação introduz uma estrutura de dados baseada em gride implementada em GPU. Ela foi desenvolvida para pesquisa dos vizinhos mais próximos em nuvens de pontos dinâmicas, de uma forma massivamente paralela. A implementação possui desempenho em tempo real e é executada em GPU, ambas construção do gride e pesquisas dos vizinhos mais próximos (exatos e aproximados). Dessa forma, a transferência de memória entre sistema e dispositivo é minimizada, aumentando o desempenho de uma forma geral. O algoritmo proposto pode ser usado em diferentes aplicações com cenários estáticos ou dinâmicos. Além disso, a estrutura de dados suporta nuvens de pontos tridimensionais e dada sua natureza dinâmica, o usuário pode mudar seus parâmetros em tempo de execução. O mesmo se aplica ao número de vizinhos pesquisados. Uma referência em CPU foi implementada e comparações de desempenho justificam o uso de GPUs como processadores massivamente paralelos. Em adição, o desempenho da estrutura de dados proposta é comparada com implementações em CPU e GPU de trabalhos anteriores. Finalmente, uma aplicação de renderização baseada em pontos foi desenvolvida de forma a verificar o potencial da estrutura de dados

Creating realistic virtual hair consists of several major areas: creating the geometry, moving the hair strands realistically and rendering the hair. In this thesis, a background survey covering each one of these areas is given. A node-based, procedural hair system is presented, which utilizes the capabilities of modern GPUs. The hair system is implemented as a plugin for Autodesk Maya, and a user interface is developed to allow the user to control the various parameters. A number of nodes are developed to create effects such as clumping, noise and frizz. The proposed system can easily handle a variety of hairstyles, and pre-renders the result in real-time using a local shading model.

Les systèmes de réalité virtuelle interactifs combinent des représentations visuelle, sonore et haptique, afin de simuler de manière immersive l'exploration d'un monde tridimensionnel représenté depuis le point de vue d'un observateur contrôlé en temps réel par l'utilisateur. La plupart des travaux effectués dans ce domaine ont historiquement port'e sur les aspects visuels (par exemple des méthodes d'affichage interactif de modèles 3D complexes ou de simulation réaliste et efficace de l'éclairage) et relativement peu de travaux ont été consacrés 'a la simulation de sources sonores virtuelles 'également dénommée auralisation. Il est pourtant certain que la simulation sonore est un facteur clé dans la production d'environnements de synthèse, la perception sonore s'ajoutant à la perception visuelle pour produire une interaction plus naturelle. En particulier, les effets sonores spatialisés, dont la direction de provenance est fidèlement reproduite aux oreilles de l'auditeur, sont particulièrement importants pour localiser les objets, séparer de multiples signaux sonores simultanés et donner des indices sur les caractéristiques spatiales de l'environnement (taille, matériaux, etc.). La plupart des systèmes de réalité virtuelle immersifs, des simulateurs les plus complexes aux jeux vidéo destin'es au grand public mettent aujourd'hui en œuvre des algorithmes de synthèse et spatialisation des sons qui permettent d'améliorer la navigation et d'accroître le réalisme et la sensation de présence de l'utilisateur dans l'environnement de synthèse. Comme la synthèse d'image dont elle est l'équivalent auditif, l'auralisation, appel'ee aussi rendu sonore, est un vaste sujet 'a la croisée de multiples disciplines : informatique, acoustique et 'électroacoustique, traitement du signal, musique, calcul géométrique mais également psycho-acoustique et perception audio-visuelle. Elle regroupe trois problématiques principales: synthèse et contrôle interactif de sons, simulation des effets de propagation du son dans l'environnement et enfin, perception et restitution spatiale aux oreilles de l'auditeur. Historiquement, ces trois problématiques émergent de travaux en acoustique architecturale, acoustique musicale et psycho-acoustique. Toutefois une différence fondamentale entre rendu sonore pour la réalité virtuelle et acoustique réside dans l'interaction multimodale et dans l'efficacité des algorithmes devant être mis en œuvre pour des applications interactives. Ces aspects importants contribuent 'a en faire un domaine 'a part qui prend une importance croissante, tant dans le milieu de l'acoustique que dans celui de la synthèse d'image/réalité virtuelle.

When creating materials in computer graphics, the most common method is to estimate the properties based on intuition. This seems like a flawed approach, seeing as a big part of the industry has already moved to a physically based workflow. A better method would be to observe real material properties, and use that data in the application. This research delves into the art of material creation by first explaining the theory behind the properties of materials through a literature review. The review also reveals techniques that separate and visually presents these properties to artists, giving them a better understanding of how a material behaves. Through action research, an empirical study then presents a workflow for creating photorealistic renders using data collected with these techniques. While the techniques still require subjective decisions when recreating the materials, they do help artists create more accurate renderings with less guesswork.

We present methods for incorporating bubbles into a photorealistc fluid simulation. Previous methods of fluid simulation in computer graphics do not include bubbles. Our system automatically creates bubbles, which are simulated on top of the fluid simulation. These bubbles are approximated by spheres and are rendered with the fluid to appear as one continuous surface. This enhances the overall realism of the appearance of a splashing fluid for computer graphics. Our methods leverage the particle level set representation of the fluid surface. We create bubbles from escaped marker particles from the outside to the inside. These marker particles might represent air that has been trapped within the fluid surface. Further, we detect when air is trapped in the fluid and create bubbles within this space. This gives the impression that the air pocket has become bubbles and is an inexpensive way to simulate the air trapped in air pockets. The results of the simulation are rendered with a raytracer that includes caustics. This allows the creation of photorealistic images. These images support our position that the simple addition of bubbles included in a fluid simulation creates results that are much more true to life.

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.

Modern machine learning methods, utilising neural networks, require a lot of training data. Data gathering and preparation has thus become a major bottleneck in the machine learning pipeline and researchers often use large public datasets to conduct their research (such as the ImageNet [1] or MNIST [2] datasets). As these methods begin being used in industry, these challenges become apparent. In factories objects being produced are often unique and may even involve trade secrets and patents that need to be protected. Additionally, manufacturing may not have started yet, making real data collection impossible. In both cases a public dataset is unlikely to be applicable. One possible solution, investigated in this thesis, is synthetic data generation. Synthetic data generation using physically based rendering was tested for unsupervised anomaly detection on a 3D printed block. A small image dataset was gathered of the block as control and a data generation model was created using its CAD model, a resource most often available in industrial settings. The data generation model used randomisation to reduce the domain shift between the real and synthetic data. For testing the data, autoencoder models were trained, both on the real and synthetic data separately and in combination. The material of the block, a white painted surface, proved challenging to reconstruct and no significant difference between the synthetic and real data could be observed. The model trained on real data outperformed the models trained on synthetic and the combined data. However, the synthetic data combined with the real data showed promise with reducing some of the bias intentionally introduced in the real dataset. Future research could focus on creating synthetic data for a problem where a good anomaly detection model already exists, with the goal of transferring some of the synthetic data generation model (such as the materials) to a new problem. This would be of interest in industries where they produce many different but similar objects and could reduce the time needed when starting a new machine learning project.

Sviluppare applicazioni grafiche al passo con la tecnologia odierna è finalmente possibile grazie alle Vulkan. Queste nuove API permettono un controllo della scheda video più diretto e ottimizzato, scalano meglio negli elaboratori multi-core e migliorano la comunicazione fra CPU e GPU. A discapito di queste caratteristiche c'è un'importante mole di informazioni e strutture dati che gli sviluppatori devono imparare a gestire, molte delle quali API precedenti come le OpenGL processavano sottobanco, e la curva di apprendimento può risultare per molti scoraggiante. Per ovviare questo aspetto la libreria V-EZ si pone come middleware di sviluppo. Fa uso degli oggetti principali di Vulkan ma al contempo riduce il carico di lavoro nascondendo allo sviluppatore gli aspetti più gravosi. Viene prima descritta la struttura di un’applicazione Vulkan generica e gli step necessari per un’inizializzazione basilare. Si introduce quindi la libreria V-EZ, confrontando gli aspetti cardini delle Vulkan e come vengono gestiti in modo semplificato. Per verificarne la bontà viene poi esposta la teoria del Physically Based Rendering, un insieme di metodi e concetti per la realizzazione di scene tridimensionali realistiche sulla base di formule fisiche, su cui viene fatta un’analisi di sviluppo utilizzando la libreria V-EZ. Il risultato è la realizzazione di un’applicazione con una difficoltà di sviluppo più bassa ma traendo comunque vantaggio delle caratteristiche di un API moderna a basso livello con un peggioramento delle prestazioni totalmente trascurabile.

In computer graphics applications, the choice and implementation of a rendering technique is crucial when targeting real-time performance. Traditionally, rasterization-based approaches have dominated the real-time sector. Other algorithms were simply too slow to compete on consumer graphics hardware. With the addition of hardware support for ray-intersection calculations on modern GPUs, hybrid ray tracing/rasterization and purely ray tracing approaches have become possible in real-time as well. Industry real-time graphics applications, namely games, have been exploring these different rendering techniques with great levels of success. The addition of ray tracing into the graphics developer’s toolkit has without a doubt increased what level of graphical fidelity is achievable in real-time. In this thesis, three rendering techniques are implemented in a custom rendering engine built on the Vulkan® Explicit API. Each technique represents a different family of modern real-time rendering algorithms. A largely rasterization-based method, a hybrid ray tracing/rasterization method, and a method solely using ray tracing. Both the hybrid and ray tracing exclusive approach rely on the ReSTIR algorithm for lighting calculations. Analysis of the performance and render quality of these approaches reveals the trade-offs incurred by each approach, alongside the performance viability of each in a real-time setting.

Placé à la frontière entre l'informatique graphique et la physique, le rendu d'image physiquement réaliste est un domaine qui tente de créer des images en simulant le comportement optique des matériaux. Les applications sont multiples : restauration virtuelle d'oeuvre du patrimoine, simulation d'effets optiques, rendu industriel pour la conception, voire même, conception assistée par ordinateur de la couleur. Cette thèse présente les travaux réalisés au cours du projet Virtuelium, un logiciel de rendu d'image physiquement réaliste dont la quatrième version a été développée dans le cadre de cette thèse. Elle en présente les principes et méthodologies utilisés pour les mesures et la validation des résultats. Nous présentons aussi plusieurs travaux réalisés durant cette thèse avec cet outil : de la restauration virtuelle à la bio-photonique sans oublier un aperçu de rendu de "matériaux à effet", pour des applications industrielles (peintures, encres, cosmétiques, etc.).

L'un des objectifs lors du développement d'un produit industriel est d'obtenir un prototype numérique valide et réaliste. Cette thèse a pour objectif d'améliorer la qualité des simulations dans le contexte d'un processus de production. Ces processus impliquent souvent un rendu de type "walkthrough", avec une géométrie fixe mais un déplacement continu de l'observateur. Nous nous intéresserons donc plus précisément aux méthodes de rendu physiquement réaliste de scènes complexes pour un scénario "walkthrough". Durant le rendu, l'utilisateur doit pouvoir mesurer précisément la radiance d'un point ou d'une zone donnée, ainsi que modifier en temps réel la puissance des sources lumineuses. Fondée sur la méthode du photon mapping, nos travaux montrent les modifications à apporter aux algorithmes afin d'améliorer à la fois la qualité des images et le temps de calcul du processus de rendu
One of the goals when developing the product is to immediately obtain a real and valid prototype. This thesis provide new rendering methods to increase the quality of the simulations during the upstream work of the production pipeline. The latter usually requires a walkthrough rendering. Thus, we focuses on the physically-based rendering methods of complex scenes in walkthrough. During the rendering, the end-users must be able to measure the illuminate rates and to interactively modify the power of the light source to test different lighting ambiances. Based on the original photon mapping method, our work shows how some modifications can decrease the calculation time and improve the quality of the resulting images according to this specific context

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

碩士
國立交通大學
多媒體工程研究所
100
Simulating realistic makeup effect is one of important research issues in the 3D facial animation and cosmetic industry. In tradition, people usually use image processing such as warping to transfer one’s makeup to another subject. But there are many disadvantages that consist of shape distortion and restriction on the similar viewing position. Besides, these methods disregard the lighting condition. Hence, we propose an integrated approach, which combines the screenspace rendering technique with the Kubelka-Munk theory, to render the 3D makeup effect. We measure many cosmetics, such as foundations, blushes and lipsticks, and we compute the parameters of Kubelka-Munk model from these data. In the rendering stage, we consider that light penetrates through the cosmetic. Therefore, we use Kubelka-Munk model to compute the total transmittance, and then we apply this value to render the appearance of human skin. Finally, we use the multi-layer theory to combine each layer together.

The rendering of participating media is an interesting and important problem without a simple solution. Yet even among the wide variety of participating media the clouds stand out as an especially difficult case, because of their properties that make their simulation even harder. The work presented in this thesis attempts to provide a solution to this problem, and moreover, to make the proposed method to work in interactive rendering speeds. The main design criteria in designing this method were its physical plausibility and maximal utilization of specific cloud properties which would help to balance the complex nature of clouds. As a result the proposed method builds on the well known photon mapping algorithm, but modifies it in several ways to obtain interactive and temporarily coherent results. This is further helped by designing the method in such a way which allows its implementation on contemporary GPUs, taking advantage of their massively parallel sheer computational power. We implement a prototype of the method in an application that renders a single realistic cloud in interactive framerates, and discuss possible extensions of the proposed technique that would allow its use in various practical industrial applications.

In computer graphics, textures are used to create detail along geometric surfaces. They are less computationally expensive than geometry, but this efficiency is traded for greater memory demands, especially with large output resolutions. Research has shown, that textures can be synthesized from low-resolution exemplars, reducing overall runtime memory cost and enabling applications, like remixing existing textures to create new, visually similar representations. In many modern applications, textures are not limited to simple images, but rather represent geometric detail in different ways, that describe how lights interacts at a certain point on a surface. Physically Based Rendering (PBR) is a technique, that employs complex lighting models to create effects like self-shadowing, realistic reflections or subsurface scattering. A set of multiple textures is used to describe what is called a material. In this thesis, example-based texture synthesis is extented to physical lighting models to create a physically based material synthesizer. It introduces a framework that is capable of utilizing multiple texture maps to synthesize new representations from existing material exemplars. The framework is then tested with multiple exemplars from different texture categories, to prospect synthesis performance in terms of quality and computation time. The synthesizer works in uv space, enabling to re-use the same exemplar material at runtime with different uv maps, reducing memory cost, whilst increasing visual varienty and minimizing repetition artifacts. The thesis shows, that this can be done effectively, without introducing inconsitencies like seams or discontiuities under dynamic lighting scenarios.:1. Context and Motivation 2. Introduction 2.1. Terminology: What is a Texture? 2.1.1. Classifying Textures 2.1.2. Characteristics and Appearance 2.1.3. Advanced Analysis 2.2. Texture Representation 2.2.1. Is there a theoretical Limit for Texture Resolution? 2.3. Texture Authoring 2.3.1. Texture Generation from Photographs 2.3.2. Computer-Aided Texture Generation 2.4. Introduction to Physically Based Rendering 2.4.1. Empirical Shading and Lighting Models 2.4.2. The Bi-Directional Reflectance Distribution Function (BRDF) 2.4.3. Typical Texture Representations for Physically Based Models 3. A brief History of Texture Synthesis 3.1. Algorithm Categories and their Developments 3.1.1. Pixel-based Texture Synthesis 3.1.2. Patch-based Texture Synthesis 3.1.3. Texture Optimization 3.1.4. Neural Network Texture Synthesis 3.2. The Purpose of example-based Texture Synthesis Algorithms 4. Framework Design 4.1. Dividing Synthesis into subsequent Stages 4.2. Analysis Stage 4.2.1. Search Space 4.2.2. Guidance Channel Extraction 4.3. Synthesis Stage 4.3.1. Synthesis by Neighborhood Matching 4.3.2. Validation 5. Implementation 5.1. Modules and Components 5.2. Image Processing 5.2.1. Image Representation 5.2.2. Filters and Guidance Channel Extraction 5.2.3. Search Space and Descriptors 5.2.4. Neighborhood Search 5.3. Implementing Synthesizers 5.3.1. Unified Synthesis Interface 5.3.2. Appearance Space Synthesis: A Hierarchical, Parallel, Per-Pixel Synthesizer 5.3.3. (Near-) Regular Texture Synthesis 5.3.4. Extented Appearance Space: A Physical Material Synthesizer 5.4. Persistence 5.4.1. Codecs 5.4.2. Assets 5.5. Command Line Sandbox 5.5.1. Providing Texture Images and Material Dictionaries 6. Experiments and Results 6.1. Test Setup 6.1.1. Metrics 6.1.2. Result Visualization 6.1.3. Limitations and Conventions 6.2. Experiment 1: Analysis Stage Performance 6.2.1. Influence of Exemplar Resolution 6.2.2. Influence of Exemplar Maps 6.3. Experiment 2: Synthesis Performance 6.3.1. Influence of Exemplar Resolution 6.3.2. Influence of Exemplar Maps 6.3.3. Influence of Sample Resolution 6.4. Experiment 3: Synthesis Quality 6.4.1. Influence of Per-Level Jitter 6.4.2. Influence of Exemplar Maps and Map Weights 7. Discussion and Outlook 7.1. Contributions 7.2. Further Improvements and Research 7.2.1. Performance Improvements 7.2.2. Quality Improvements 7.2.3. Methology 7.2.4. Further Problem Fields

The goal of computer graphics is to precisely model the appearance of real objects. It includes of interactions of light with various materials. Polarisation is one of the fundamental properties of light. Incorporating polarisation parameter into an illumination model can significantly enhance the physical realism of rendered images in the case of scenes including multiple light bounces via specular surfaces, etc. However, recent rendering systems do not take polarisation into account because of complexity of such a solution. The key component for obtaining physically correct images are realistic, polarisation capable BRDF (Bidirectional Reflectance Distribution Function) models. Within this thesis, polarising versions of the following BRDF models were theoretically derived: Torrance Sparrow, He-Torrance-Sillion-Greenberg and Weidlich-Wilkie. For each of these models, Mueller matrices (the mathematical construct used to describe polarising surface reflectance) were systematically derived and their behaviour tested under various input parameters using Wolfram Mathematica. Derived polarising glossy BRDF models were further implemented using a rendering research system, ART (Advanced Rendering Toolkit). As far as we know, it is the very first usage of these BRDF models in a polarisation renderer....