In computer graphics, the complex phenomenon of color appearance, involving the interaction of light, matter and the human visual system, is modeled by the multiplication of RGB triplets assigned to lights and materials. This efficient heuristic produces plausible images because the triplets assigned to materials usually function as color specifications. To predict color, spectral rendering is required, but the O(n) cost of computing reflections with n-dimensional point-sampled spectra is prohibitive for real-time rendering. Typical spectra are well approximated by m-dimensional linear models, where m << n, but computing reflections with this representation requires O(m^2) matrix-vector multiplication. A method by Drew and Finlayson [JOSA A 20, 7 (2003), 1181-1193], reduces this cost to O(m) by “sharpening” an n x m orthonormal basis with a linear transformation, so that the new basis vectors are approximately disjoint. If successful, this transformation allows approximated reflections to be computed as the products of coefficients of lights and materials. Finding the m x m change of basis matrix requires solving m eigenvector problems, each needing a choice of wavelengths in which to sharpen the corresponding basis vector. These choices, however, are themselves an optimization problem left unaddressed by the method's authors. Instead, we pose a single problem, expressing the total approximation error incurred across all wavelengths as the sum of dm^2 squares for some number d, where, depending on the inherent dimensionality of the rendered reflectance spectra, m <= d << n, a number that is independent of the number of approximated reflections. This problem may be solved in real time, or nearly, using standard nonlinear optimization algorithms. Results using a variety of reflectance spectra and three standard illuminants yield errors at or close to the best lower bound attained by projection onto the leading m characteristic vectors of the approximated reflections. Measured as CIEDE2000 color differences, a heuristic proxy for image difference, these errors can be made small enough to be likely imperceptible using values of 4 <= m <= 9. An examination of this problem reveals a hierarchy of simpler, more quickly solved subproblems whose solutions yield, in the typical case, increasingly inaccurate approximations. Analysis of this hierarchy explains why, in general, the lowest approximation error is not attained by simple spectral sharpening, the smallest of these subproblems, unless the spectral power distributions of all light sources in a scene are sufficiently close to constant functions. Using the methods described in this dissertation, spectra can be rendered in real time as the products of m-dimensional vectors of sharp basis coefficients at a cost that is, in a typical application, a negligible fraction above the cost of RGB rendering. / Graduate

Background. Instant replay allows an application to highlight events without exporting a video of the whole session. Hardware-accelerated video encoding allows replay footage to be encoded in real-time with less to no impact on the runtime performance of the actual simulation in the application. Hardware-accelerated video encoding, however, is not supported on all devices such as low-tier mobile devices, nor all platforms like web browsers. When hardware-acceleration is not supported, the replay has to be encoded using a software-implemented encoder instead. Objectives. To evaluate if recording rendering API commands is a suitable replacement of real-time encoding when hardware-accelerated video encoding is not supported. Method. An experimental research method is used to make quantitative measurements of the proposed approach, Reincore, and a real-time encoder. The measured metrics is frame time and memory consumption. The Godot game engine is modified with modules for real-time video encoding (H.264, H.265 and VP9 codecs) and rendering API command recording and replaying. The engine is also used to create test scenes to evaluate if object count, image motion, object loading/unloading, replay video resolution and replay video duration has any impact on the runtime overhead of frame time and memory consumption. Results. The implemented rendering API command replayer, Reincore, appears to have minimal to no impact on the frame time overhead in all scenarios, except for a spike in increased frame time when the replayer initializes synchronization. Reincore show to be overall inferior to real-time video encoding in terms of runtime memory overhead. Conclusions. Overall, real-time encoding using the H.264 or H.265 show a similar result in frame time as recording rendering commands. However, command recording implies a more significant overhead of memory usage than real-time encoding. The frame time of using the VP9 codec for real-time encoding is inferior to recording rendering API commands. / Bakgrund. Återspelning tillåter applikationer att visa upp händelser utan att exportera en video för hela sessionen. Hårdvaruaccelererad videokodning tillåter video av återspelning att kodas i realtid med minimal påverkan på applikationens prestanda för simulering. Hårdvaruaccelererad videokodning stöds dock inte alltid på alla enheter eller plattformar, så som lågt presterande mobila enheter eller webbläsare. När hårdvaruacceleration inte stöds, måste videokodning ske med en mjukvarubaserad implementering istället. Syfte. Att utvärdera om återspelning genom inspelade renderingskommandon som fördröjer arbetet för videokodning är ett lämpligt alternativ till videokodning i realtid, när hårdvaruacceleration inte stöds. Metod. En experimentel forskningsmetod används för att samla kvantitativ mätdata från den föreslagna tillvägagången, Reincore, and en realtidsvidekodare. Mätdatan består av bildtid och minnesanvändning. Genom att modifiera spelmotorn Godot skapas moduler för realtids-videokodning samt inspelning av renderingskommandon. Spelmotorn används också för att skapa testscener för att utvärdera om antal objekt, bildrörelse, skapande av objekt under körning, upplösning eller videolängd har någon inverkan på bildtid eller minnesanvändning. Resultat. Den implementerade renderingskommando-inspelaren, Reincore, visar minimal påverkan på bildtid, med undantag för en temporär ökning när återspelaren initierar synkronisering. Reincore visar sig vara underlägsen till realtids-videokodning när det gäller minnesanvändning. Slutsatser. Realtids-videokodning med H.264 eller H.265 som video-codec visar övergripande bättre resultat för återspelning än renderingskommandoinspelning, när det gäller både bildtid samt minnesanvändning. Bildtiden för VP9 video-codec för realtids-videokodning visar däremot sämre resultat än renderingskommandinspelning.

Current commercial Virtual Reality (VR) headsets give viewers immersion in virtual space with stereoscopic graphics and positional tracking. Developers can create VR applications in a working pipeline similar to creating 3D games using game engines. However, the characteristics of VR headsets give disadvantages to the rendering technique particle system with billboard sprites. In our study, we propose a rendering technique called FOggy-LAser Rendering method (FOLAR), which renders realistic laser in fog on billboard sprites. With this method, we can compensate for the disadvantages of using particle systems and still render the graphics in interactive performance for VR. We studied the characteristics of this method by performance benchmarks and comparing the rendered result to a baseline ray-casting method. User study and image similarity metrics are involved in the comparison study. As a result, we observed a satisfying performance and a similar rendering result compared to ray-casting. However, the user study still shows a significant difference in the rendered result between methods. These results imply that FOLAR is an acceptable method for its performance and ness in the rendered result, but still have inevitable trade-offs‌‌‌ in the graphics. / Nuvarande kommersiella Virtual Reality (VR) headset ger användare immersion i virtuellt utrymme med stereoskopisk grafik och positionsspårning. Utvecklare kan skapa VR-applikationer i en fungerande pipeline på ett liknande sätt som att skapa 3D-spel med hjälp av spelmotorer. Egenskaperna hos VR-headset ger emellertid nackdelar med renderingstekniken av billboard sprite partikelsystem. I vår studie föreslår vi en renderingsteknik som kallas FOggy-LAser Rendering method (FOLAR), som renderar realistiska lasrar i dimma på billboard sprites. Med denna metod kan vi kompensera för nackdelarna med att använda partikelsystem och fortfarande göra grafiken i interaktiv prestanda för VR. Vi studerade egenskaperna hos denna metod genom prestanda benchmarks och jämförde renderade resultatet med en baseline ray-cast metod. Användarstudie och image similarity mätvärden är involverade i jämförelsestudien. Som resultat observerade vi en tillfredsställande prestanda och liknande renderings resultat jämfört med ray-casting. Dock visar användarstudien fortfarande en signifikant skillnad i det gjorda resultaten mellan metoderna. Dessa resultat pekar på att FOLAR är en acceptabel metod för dess prestanda och korrekthet i det renderade resultatet, men har fortfarande oundvikliga avvägningar i grafiken.

Realistic rendering of 3D graphics scenes often requires large amounts of data and processing. High resolution texture data, complex BRDFs, surface modification, and global illumination effects are often necessary to realistically render a synthetic scene, but achieving such effects with a reasonable balance between performance and quality in real-time remains a challenge. Virtual texture techniques have been developed in order to manage extremely high resolution texture data. This thesis describes the implementation of a technique which allows writing of projected texture data to a virtual texture in real-time, allowing infinite numbers of permanent highly detailed surface modifications without the performance or accuracy limitations of decal techniques used in current games. It also describes an implementation of a real-time renderer which uses measured BRDF data, and discusses how applying virtual texturing to measured BRDF data may allow accurate, fast rendering with realistic materials. Finally, it discusses how the virtual decal system can be used to allow artists or game players to interactively alter the material composition of scenes with many distinct measured BRDFs.

On retrouve dans la nature un nombre impressionnant de matériaux semi-transparents tels le marbre, le jade ou la peau, ainsi que plusieurs liquides comme le lait ou les jus. Que ce soit pour le domaine cinématographique ou le divertissement interactif, l'intérêt d'obtenir une image de synthèse de ce type de matériau demeure toujours très important. Bien que plusieurs méthodes arrivent à simuler la diffusion de la lumière de manière convaincante a l'intérieur de matériaux semi-transparents, peu d'entre elles y arrivent de manière interactive. Ce mémoire présente une nouvelle méthode de diffusion de la lumière à l'intérieur d'objets semi-transparents hétérogènes en temps réel. Le coeur de la méthode repose sur une discrétisation du modèle géométrique sous forme de voxels, ceux-ci étant utilisés comme simplification du domaine de diffusion. Notre technique repose sur la résolution de l'équation de diffusion à l'aide de méthodes itératives permettant d'obtenir une simulation rapide et efficace. Notre méthode se démarque principalement par son exécution complètement dynamique ne nécessitant aucun pré-calcul et permettant une déformation complète de la géométrie. / We find in nature several semi-transparent materials such as marble, jade or skin, as well as liquids such as milk or juices. Whether it be for digital movies or video games, having an efficient method to render these materials is an important goal. Although a large body of previous academic work exists in this area, few of these works provide an interactive solution. This thesis presents a new method for simulating light scattering inside heterogeneous semi-transparent materials in real time. The core of our technique relies on a geometric mesh voxelization to simplify the diffusion domain. The diffusion process solves the diffusion equation in order to achieve a fast and efficient simulation. Our method differs mainly from previous approaches by its completely dynamic execution requiring no pre-computations and hence allowing complete deformations of the geometric mesh.

[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.

No description available.

[pt] Este trabalho apresenta um novo sistema de renderização distribuída destinado ao uso em agrupamentos de PCs. É feita uma extensão à linha de produção gráfica convencional para uma linha de produção gráfica distribuída, que pelo uso de múltiplas linhas de execução permite paralelizar as operações feitas na CPU, na GPU e na rede que interliga os PCs do agrupamento. Este sistema serviu de base para a implementação e o teste de três arquiteturas para renderização distribuída: uma arquitetura com ordenação no início, uma arquitetura com ordenação no fim para renderização volumétrica e uma arquitetura híbrida que tenta combinar as vantagens da ordenação no início e da ordenação no fim. É apresentado um novo algoritmo de balanceamento de carga baseado nos tempos de renderização do quadro anterior. O algoritmo é de implementação muito simples e funciona bem tanto em aplicações com gargalo na geometria quanto em aplicações com gargalo na rasterização. Este trabalho também propõe uma estratégia de distribuição de trabalho entre os computadores de renderização do agrupamento que usa eficientemente os recursos gráficos disponíveis, melhorando assim o desempenho da renderização. Um novo algoritmo de partição paralela do modelo entre os computadores do agrupamento é proposto para a arquitetura híbrida. / [en] This work presents a new distributed rendering system destined for PC clusters. The conventional graphics pipeline is extended to a distributed pipeline that parallelizes the operations done on the CPU, the GPU and the network by using multiple threads. This system was the base for the implementation of three distributed rendering architectures: a sort-first architecture, a sort-last architecture for volume rendering, and a hybrid architecture that seeks to combine the advantages of both sort-first and sortlast architectures. A new load-balancing algorithm based on the rendering times of the previous frame is proposed. The algorithm is very simple to be implemented and works well for both geometry- and rasterization-bound models. A new strategy to assign tiles to rendering nodes is proposed which effectively uses the available graphics resources, thus improving rendering performance. A new parallel model partition algorithm is proposed for the hybrid architecture.

Shader programming is important for realistic material and global illumination real-time rendering, especially in 3D industrial fields nowadays, more and more customers of Visual Components Oy, a Finnish 3D software company have been found to be no longer only content with the correct simulation result, but also the result of realistic real-time rendering. This thesis project will provide a deep research on real world material classification, property definition and global illumination techniques in industrial fields. On the other hand, the Shader program for different materials and global illumination techniques are also created according to the classification and definition in this thesis work. Moreover, an external rendering tool Redway3D is evaluated as the reference and regarded as the considerable solution in the future development work.

On retrouve dans la nature un nombre impressionnant de matériaux semi-transparents tels le marbre, le jade ou la peau, ainsi que plusieurs liquides comme le lait ou les jus. Que ce soit pour le domaine cinématographique ou le divertissement interactif, l'intérêt d'obtenir une image de synthèse de ce type de matériau demeure toujours très important. Bien que plusieurs méthodes arrivent à simuler la diffusion de la lumière de manière convaincante a l'intérieur de matériaux semi-transparents, peu d'entre elles y arrivent de manière interactive. Ce mémoire présente une nouvelle méthode de diffusion de la lumière à l'intérieur d'objets semi-transparents hétérogènes en temps réel. Le coeur de la méthode repose sur une discrétisation du modèle géométrique sous forme de voxels, ceux-ci étant utilisés comme simplification du domaine de diffusion. Notre technique repose sur la résolution de l'équation de diffusion à l'aide de méthodes itératives permettant d'obtenir une simulation rapide et efficace. Notre méthode se démarque principalement par son exécution complètement dynamique ne nécessitant aucun pré-calcul et permettant une déformation complète de la géométrie. / We find in nature several semi-transparent materials such as marble, jade or skin, as well as liquids such as milk or juices. Whether it be for digital movies or video games, having an efficient method to render these materials is an important goal. Although a large body of previous academic work exists in this area, few of these works provide an interactive solution. This thesis presents a new method for simulating light scattering inside heterogeneous semi-transparent materials in real time. The core of our technique relies on a geometric mesh voxelization to simplify the diffusion domain. The diffusion process solves the diffusion equation in order to achieve a fast and efficient simulation. Our method differs mainly from previous approaches by its completely dynamic execution requiring no pre-computations and hence allowing complete deformations of the geometric mesh.