178 research outputs found

    Lazy visibility evaluation for exact soft shadows

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    International audienceThis report presents a novel approach to compute high quality and alias-free soft shadows using exact visibility computations. This work relies on a theoritical framework allowing to group lines according to the geometry they intersect. From this study, we derive a new algorithm encoding lazily the visibility from a polygon. Contrary to previous works on from-polygon visibility, our approach is very robust and straightforward to implement. We apply this algorithm to solve exactly and efficiently the visibility of an area light source from any point in a scene. As a consequence, results are not sensitive to noise, contrary to soft shadows methods based on area light source sampling. We demonstrate the reliability of our approach on different scenes and configurations

    Lazy visibility evaluation for exact soft shadows

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    Présentation invitée de l'article du même nom publié en 2012 dans la revue Computer Graphics Forum.International audienceThis paper presents a novel approach to compute high quality and noise-free soft shadows using exact visibility computations. This work relies on a theoretical framework allowing to group lines according to the geometry they intersect. From this study, we derive a new algorithm encoding lazily the visibility from a polygon. Contrary to previous works on from-polygon visibility, our approach is very robust and straightforward to implement. We apply this algorithm to solve exactly and efficiently the visibility of an area light source from any point in a scene. As a consequence, results are not sensitive to noise, contrary to soft shadows methods based on area light source sampling. We demonstrate the reliability of our approach on different scenes and configurations

    Real-time soft shadows using a single light sample

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    We present a real-time rendering algorithm that generates soft shadows of dynamic scenes using a single light sample. As a depth-map algorithm it can handle arbitrary shadowed surfaces. The shadow-casting surfaces, however, should satisfy a few geometric properties to prevent artifacts. Our algorithm is based on a bivariate attenuation function, whose result modulates the intensity of a light causing shadows. The first argument specifies the distance of the occluding point to the shadowed point; the second argument measures how deep the shadowed point is inside the shadow. The attenuation function can be implemented using dependent texture accesses; the complete implementation of the algorithm can be accelerated by today's graphics hardware. We outline the implementation, and discuss details of artifact prevention and filtering

    Realtime ray tracing and interactive global illumination

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    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

    Real-time Global Illumination by Simulating Photon Mapping

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    A New Mathematical Development for Radiosity Animation with Galerkin

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    International audienceCombining animation and global illumination constitutes, at present, a true challenge in computer graphics, especially when light sources move in a complex scene because the entire illumination has to be recomputed. This paper introduces a new algorithm, based on the Galerkin method, which can efficiently manage any moving surface -even light source- to compute animation sequences. For each new frame of a sequence, we take into account the continuous property of the moves to determine the necessary energy differences between the previous global illumination solution and the new one. Based on a mathematical development of the form factor, this new approach leads to an efficient and simple algorithm, similar to the classical progressive refinement algorithm, and which computes animated sequence about three times faster

    Real-time shadows for animated crowds in virtual cities

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