Parallelization of hierarchical radiosity algorithms on distributed memory computers

Ankara : Department of Computer Engineering and Information Science and the Institute of Engineering and Science of Bilkent Univ., 1998.Thesis (Master's) -- Bilkent University, 1998.Includes bibliographical references leaves 93-97.Şireli, Ahmet ReşatM.S

Vertex-Tracing - Interaktives Ray-Tracing durch adaptiv progressives Refinement im Objektraum

Abstract This dissertation presents an approach for interactive, physically exact simulation of specular reflections and specular refractions in virtual environments. The introduced approach is called Vertex Tracing and allows a hybrid rendering to add global illumination effects in traditional hardware rendering systems. The core of the Vertex Tracing is an adaptive progressive ray tracing. In contrast to standard ray tracing we use image coherence to compute only pixels (samples) that are essential for the final image reconstruction. The step by step adaption towards the final image is performed by geometry refinement of chosen polyhedra. These are scene objects with visual characteristics as specular reflections or refractions and should be handled particularly for Vertex Tracing. The object vertices are the starting point of computation. First, primary rays are shot from the eye point to the object vertices and after that, like in classical ray tracing approaches, a recursive ray shooting is performed from each vertex. If needed new vertices are inserted and consequently a step by step refinement of the object geometry is done. The reconstruction of the final image is performed by bilinear interpolation via graphics hardware. Beside the possibility of a combined rendering with OpenGL-objects, the use of graphics hardware additionally allows an efficient handling of textures. In this context, we introduce a defered texture lookup to prevent a costly sampling of high frequent textures. In addition, this thesis considers aspects of a distributed and parallel computation to speed up Vertex Tracing. In detail we implemented a distributed Vertex Tracing for a heterogenous network as well as a parallel approach for shared memory machines. Despite the adaptive progressive characteristic of the Vertex Tracing both techniques show that a significant speed-up can be achieved.Die vorliegende Dissertation beschreibt ein Verfahren zur interaktiv physikalisch exakten Simulation spekularer Reflexionen sowie spekularer Brechungen in virtuellen Umgebungen. Unter dem Begriff Vertex-Tracing wird in dieser Arbeit ein Ansatz vorgestellt, der es durch hybrides Rendering erlaubt, traditionelles Hardware-Rendering mit globalen Beleuchtungsphänomenen zu ergänzen. Kern des Verfahrens Vertex-Tracing bildet ein adaptiv progressives Ray-Tracing. Im Gegensatz zum Standard-Ray-Tracing besteht das Ziel darin, vorhandene Bildkohärenzen auszunutzen, indem nur diejenigen Pixel (Samples) berechnet werden, die für die Rekonstruktion des Finalbildes erforderlich sind. Die schrittweise Annäherung an das gewünschte Finalbild erfolgt durch Verfeinerung (Refinement) der Geometrie ausgewählter Polyeder. Diese sind Szenenobjekte, die aufgrund ihrer visuellen Charakteristik in Form spekularer Reflexionen oder Brechungen einem Vertex-Tracing unterzogen werden sollen. Ausgangspunkt der Berechnung dieser Objekte stellen ihre Objekt-Vertices dar. Sie bilden jeweils den Aufpunkt eines geschossenen Primärstrahles vom Betrachter und sind zugleich Startpunkt für eine weitere rekursive Strahlenverfolgung im Sinne des klassischen Ray-Tracing. Je nach Bedarf erfolgt das Einfügen neuer Vertices, dass eine schrittweise Verfeinerung der Objektgeometrie nach sich zieht. Die Rekonstruktion des Finalbildes erfolgt durch bilineare Interpolation mit Hilfe von Graphik-Hardware. Ihre Nutzung gestattet nicht nur ein kombiniertes Rendering mit herkömmlichen OpenGL-Objekten, sondern erlaubt darüber hinaus eine effiziente Behandlung von Texturen im Vertex-Tracing. In diesem Zusammenhang wird ein verzögerter Textur-Lookup vorgestellt. Er verhindert ein vollständiges Sampling von Texturen, das vor allem bei hochfrequenten Texturen einen erheblichen Mehraufwand bedeuten würde. Im Hinblick auf die Beschleunigung des Verfahrens werden ferner Aspekte einer verteilt, parallelen Berechnung untersucht beziehungsweise umgesetzt. Im Vordergrund steht dabei die Verteilung des Vertex-Tracings im Rechner-Cluster sowie eine Parallelisierung des Algorithmus auf Shared-Memory-Maschinen. Beide Ansätze zeigen, dass trotz des adaptiv progressiven Charakters des Verfahrens Vertex-Tracing ein signifikanter Speed-Up erzielbar ist

The distributed ASCI supercomputer project

The Distributed ASCI Supercomputer (DAS) is a homogeneous wide-area distributed system consisting of four cluster computers at different locations. DAS has been used for research on communication software, parallel languages and programming systems, schedulers, parallel applications, and distributed applications. The paper gives a preview of the most interesting research results obtained so far in the DAS project

Supercomputer networking for space science applications

The initial design of a supercomputer network topology including the design of the communications nodes along with the communications interface hardware and software is covered. Several space science applications that are proposed experiments by GSFC and JPL for a supercomputer network using the NASA ACTS satellite are also reported

Application level runtime load management : a bayesian approach

A computação paralela em sistemas distribuídos partilhados exige novas abordagens ao problema da gestão da carga computacional, uma vez que os algoritmos existentes ficam aquém das expectativas. A execução eficiente de aplicações paralelas irregulares em clusters de computadores partilhados dinamicamente exibe um comportamento imprevisível, devido à à variabilidade dos requisitos da aplicação e da disponibilidade dos recursos do sistema. Esta tese investiga as vantagens de incluir explicitamente no modelo de execução de um escalonador ao nível da aplicação a incerteza que este tem sobre o estado do ambiente em cada instante. Propõe-se um mecanismo de decisão baseado em redes de decisão de Bayes, complementado por uma estrutura genérica para estas redes, vocacionada para o escalonamento ao nível da aplicação; a utilização de um algoritmo de inferência probabilística permite ao escalonador tomar decisões mais eficazes, baseadas em previsões escolásticas das consequências destas decisões, geradas a partir de informação incompleta e desactualizada sobre o estado do ambiente. É proposto um modelo de desempenho da aplicação e respectivas métricas, que permite prever o comportamento da aplicação e do sistema distribuído; estas métricas são utilizadas quer no mecanismo de decisão do escalonador, quer para avaliar o desempenho do mesmo. Para verificar se esta abordagem contribui para melhorar o tempo de execução das aplicações e a eficiência do escalonador, foi desenvolvido um ray tracer paralelo, representativo de uma classe de aplicações baseada em passagem de mensagens com paralelismo no domínio dos dados e comportamento irregular. Este protótipo foi executado num cluster com sete nodos partilhados no tempo e submetidos a vários padrões sintéticos de cargas de trabalho dinâmicas. Para avaliar a eficácia da gestão de carga proposta, o desempenho do escalonador estocástico foi comparado com três escalonadores de referência: uma distribuição estática e uniforme da carga, uma estratégia orientada ao pedido e uma política de escalonamento determinística baseada em sensores. Os resultados obtidos demonstram que estratégias dinâmicas baseadas em sensores obtêm grandes melhorias de desempenho sobre estratégias que não usam informação sobre o estado do ambiente, e realçam as vantagens do escalonador estocástico relativamente a um escalonador determinístico com um nível de complexidade equivalente.Affordable parallel computing on distributed shared systems requires novel approaches to manage the runtime load distribution, since current algorithms fall below expectations. The efficient execution of irregular parallel applications, on dynamically shared computing clusters, has an unpredictable dynamic behaviour, due both to the application requirements and to the available system's resources. This thesis addresses the explicit inclusion of the uncertainty an application level scheduling agent has about the environment, on its internal model of the world and on its decision making mechanism. Bayesian decision networks are introduced and a generic framework is proposed for application level scheduling, where a probabilistic inference algorithm helps the scheduler to efficiently make decisions with improved predictions, based on available incomplete and aged measured data. An application level performance model and associated metrics (performance, environment and overheads) are proposed to obtain application and system behaviour estimates, to include in the scheduling agent's model and to help the evaluation. To verify that this novel approach improves the overall application execution time and the scheduling efficiency, a parallel ray tracer was developed as a message passing irregular data parallel application, and an execution model prototype was built to run on a seven time-shared nodes computing cluster, with dynamically variable synthetic workloads. To assess the effectiveness of the load management, the stochastic scheduler was evaluated rendering several complex scenes, and compared with three reference scheduling strategies: a uniform work distribution, a demand driven work allocation and a sensor based deterministic scheduling strategy. The evaluation results show considerable performance improvements over blind strategies, and stress the decision network based scheduler improvements over the sensor based deterministic approach of identical complexity.Fundação para a Ciência e Tecnologia - PRAXIS XXI 2/2.1/TTT/1557/95

Actas do 10º Encontro Português de Computação Gráfica

Actas do 10º Encontro Portugês de Computação Gráfica, Lisboa, 1-3 de Outubro de 2001A investigação, o desenvolvimento e o ensino na área da Computação Gráfica constituem, em Portugal, uma realidade positiva e de largas tradições. O Encontro Português de Computação Gráfica (EPCG), realizado no âmbito das actividades do Grupo Português de Computação Gráfica (GPCG), tem permitido reunir regularmente, desde o 1º EPCG realizado também em Lisboa, mas no já longínquo mês de Julho de 1988, todos os que trabalham nesta área abrangente e com inúmeras aplicações. Pela primeira vez no historial destes Encontros, o 10º EPCG foi organizado em ligação estreita com as comunidades do Processamento de Imagem e da Visão por Computador, através da Associação Portuguesa de Reconhecimento de Padrões (APRP), salientando-se, assim, a acrescida colaboração, e a convergência, entre essas duas áreas e a Computação Gráfica. Este é o livro de actas deste 10º EPCG.INSATUniWebIcep PortugalMicrografAutodes

Realtime ray tracing and interactive global illumination

One of the most sought-for goals in computer graphics is to generate "realism in real time". i.e. the generation of realistically looking images at realtime frame rates. Today, virtually all approaches towards realtime rendering use graphics hardware, which is based almost exclusively on triangle rasterization. Unfortunately, though this technology has seen tremendous progress over the last few years, for many applications it is currently reaching its limits in both model complexity, supported features, and achievable realism. An alternative to triangle rasterizations is the ray tracing algorithm, which is well-known for its higher flexibility, its generally higher achievable realism, and its superior scalability in both model size and compute power. However, ray tracing is also computationally demanding and thus so far is used almost exclusively for high-quality offline rendering tasks. This dissertation focuses on the question why ray tracing is likely to soon play a larger role for interactive applications, and how this scenario can be reached. To this end, we discuss the RTRT/OpenRT realtime ray tracing system, a software based ray tracing system that achieves interactive to realtime frame rates on todays commodity CPUs. In particular, we discuss the overall system design, the efficient implementation of the core ray tracing algorithms, techniques for handling dynamic scenes, an efficient parallelization framework, and an OpenGL-like low-level API. Taken together, these techniques form a complete realtime rendering engine that supports massively complex scenes, highley realistic and physically correct shading, and even physically based lighting simulation at interactive rates. In the last part of this thesis we then discuss the implications and potential of realtime ray tracing on global illumination, and how the availability of this new technology can be leveraged to finally achieve interactive global illumination - the physically correct simulation of light transport at interactive rates.Eines der wichtigsten Ziele der Computer-Graphik ist die Generierung von "Realismus in Echtzeit\u27; — die Erzeugung von realistisch wirkenden, computer- generierten Bildern in Echtzeit. Heutige Echtzeit-Graphikanwendungen werden derzeit zum überwiegenden Teil mit schneller Graphik-Hardware realisiert, welche zum aktuellen Stand der Technik fast ausschliesslich auf dem Dreiecksrasterisierungsalgorithmus basiert. Obwohl diese Rasterisierungstechnologie in den letzten Jahren zunehmend beeindruckende Fortschritte gemacht hat, stößt sie heutzutage zusehends an ihre Grenzen, speziell im Hinblick auf Modellkomplexität, unterstützte Beleuchtungseffekte, und erreichbaren Realismus. Eine Alternative zur Dreiecksrasterisierung ist das "Ray-Tracing\u27; (Stahl-Rückverfolgung), welches weithin bekannt ist für seine höhere Flexibilität, seinen im Großen und Ganzen höheren erreichbaren Realismus, und seine bessere Skalierbarkeit sowohl in Szenengröße als auch in Rechner-Kapazitäten. Allerdings ist Ray-Tracing ebenso bekannt für seinen hohen Rechenbedarf, und wird daher heutzutage fast ausschließlich für die hochqualitative, nichtinteraktive Bildsynthese benutzt. Diese Dissertation behandelt die Gründe warum Ray-Tracing in näherer Zukunft voraussichtlich eine größere Rolle für interaktive Graphikanwendungen spielen wird, und untersucht, wie dieses Szenario des Echtzeit Ray-Tracing erreicht werden kann. Hierfür stellen wir das RTRT/OpenRT Echtzeit Ray-Tracing System vor, ein software-basiertes Ray-Tracing System, welches es erlaubt, interaktive Performanz auf heutigen Standard-PC-Prozessoren zu erreichen. Speziell diskutieren wir das grundlegende System-Design, die effiziente Implementierung der Kern-Algorithmen, Techniken zur Unterstützung von dynamischen Szenen, ein effizientes Parallelisierungs-Framework, und eine OpenGL-ähnliche Anwendungsschnittstelle. In ihrer Gesamtheit formen diese Techniken ein komplettes Echtzeit-Rendering-System, welches es erlaubt, extrem komplexe Szenen, hochgradig realistische und physikalisch korrekte Effekte, und sogar physikalisch-basierte Beleuchtungssimulation interaktiv zu berechnen. Im letzten Teil der Dissertation behandeln wir dann die Implikationen und das Potential, welches Echtzeit Ray-Tracing für die Globale Beleuchtungssimulation bietet, und wie die Verfügbarkeit dieser neuen Technologie benutzt werden kann, um letztendlich auch Globale Belechtung — die physikalisch korrekte Simulation des Lichttransports — interaktiv zu berechnen

Realtime ray tracing on current CPU architectures

In computer graphics, ray tracing has become a powerful tool for generating realistically looking images. Even though ray tracing offers high flexibility, a logarithmic scalability in scene complexity, and is known to be efficiently parallelizable, its demand for compute power has in the past lead to its limitation to high-quality off-line rendering. This thesis focuses on the question of how realtime ray tracing can be realized on current processor architectures. To this end, it provides a detailed analysis of the weaknesses and strengths of current processor architectures, for the purpose of allowing for highly optimized implementation. The combination of processor-specific optimizations with algorithms that exploit the coherence of ray tracing, makes it possible to achieve realtime performance on a single CPU. Besides the optimization of the ray tracing algorithm itself, this thesis focuses on the efficient building of spatial index structures. By building these structures from scratch for every frame, interactive ray tracing of fully dynamic scenes becomes possible. Moreover, a parallelization framework for ray tracing is discussed that efficiently exploits the compute power of a cluster of commodity PCs. Finally, a global illumination algorithm is proposed that efficiently combines optimized ray tracing and the parallelization framework. The combination makes it possible to compute complete global illumination at interactive frame rates

An Analytical model for the colorimetric characterization of color CRTs

To be a viable instrument for color appearance research, the color Cathode Ray Tube has to be very well calibrated and characterized. The purpose of this research was to develop the techniques and methods used to carry out such characterization, and also to evaluate to what degree of precision and accuracy can such a characterization be performed. A new model for predicting the CRT behavior is presented along with the experimental results that validate it