125 research outputs found

    Fast, effective BVH updates for dynamic ray-traced scenes using tree rotations

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    technical reportBounding volume hierarchies are a popular choice for ray tracing animated scenes due to the relative simplicity of refitting bounding volumes around moving geometry. However, the quality of such a refitted tree can degrade rapidly if objects in the scene deform or rearrange significantly as the animation progresses, resulting in dramatic increases in rendering times. Existing solutions involve occasional or heuristically triggered rebuilds of the BVH to reduce this effect. In this work, we describe how to efficiently extend refitting with local restructuring operations called tree rotations which can mitigate the effects that moving primitives have on BVH quality by rearranging nodes in the tree during each refit rather than triggering a full rebuild. The result is a fast, lightweight, incremental update algorithm that requires negligible memory, has minor update times and parallelizes easily, yet avoids significant degradation in tree quality or the need for rebuilding while maintaining fast rendering times. We show that our method approaches or exceeds the frame rates of other techniques and is consistently among the best options regardless of the animation scene

    Doctor of Philosophy

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    dissertationThis dissertation explores three key facets of software algorithms for custom hardware ray tracing: primitive intersection, shading, and acceleration structure construction. For the first, primitive intersection, we show how nearly all of the existing direct three-dimensional (3D) ray-triangle intersection tests are mathematically equivalent. Based on this, a genetic algorithm can automatically tune a ray-triangle intersection test for maximum speed on a particular architecture. We also analyze the components of the intersection test to determine how much floating point precision is required and design a numerically robust intersection algorithm. Next, for shading, we deconstruct Perlin noise into its basic parts and show how these can be modified to produce a gradient noise algorithm that improves the visual appearance. This improved algorithm serves as the basis for a hardware noise unit. Lastly, we show how an existing bounding volume hierarchy can be postprocessed using tree rotations to further reduce the expected cost to traverse a ray through it. This postprocessing also serves as the basis for an efficient update algorithm for animated geometry. Together, these contributions should improve the efficiency of both software- and hardware-based ray tracers

    Bandwidth and memory efficiency in real-time ray tracing

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    Real time ray tracing has been given a lot of attention in recent years in the academic and research community. Several novel algorithms have appeared that parallelize different aspects of the ray tracing algorithm through the use of a GPU. Among these, the creation of Bounding Volume Hierarchies (BVHs). We believe that recent approaches have failed to consider the performance impact of memory accesses in GPU and how their cost affects the overall performance of the application. In this work we show that by reducing memory bandwidth and footprint we are able to achieve significant improvements in BVH traversal times. We do this by compressing the BVH and the triangle mesh in a parallel manner after its creation, in each frame, and then decompressing it as needed while traversing the BVH

    Bounding Volume Hierarchies for Collision Detection

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    In virtual environment world, performing collision detection between various 3D objects requires sophisticated steps to be followed in order to properly visualize their effect. It is challenging due to the fact that multiple objects undergo various motion depending on the application’s genre. It is however an essential challenge to be resolved since it’s many use in the computer animation, simulation and robotic industry. Thus, object intersection between rigid bodies has become one of the most important areas in order to bring realism to simulation and animation

    Hardware Accelerators for Animated Ray Tracing

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    Future graphics processors are likely to incorporate hardware accelerators for real-time ray tracing, in order to render increasingly complex lighting effects in interactive applications. However, ray tracing poses difficulties when drawing scenes with dynamic content, such as animated characters and objects. In dynamic scenes, the spatial datastructures used to accelerate ray tracing are invalidated on each animation frame, and need to be rapidly updated. Tree update is a complex subtask in its own right, and becomes highly expensive in complex scenes. Both ray tracing and tree update are highly memory-intensive tasks, and rendering systems are increasingly bandwidth-limited, so research on accelerator hardware has focused on architectural techniques to optimize away off-chip memory traffic. Dynamic scene support is further complicated by the recent introduction of compressed trees, which use low-precision numbers for storage and computation. Such compression reduces both the arithmetic and memory bandwidth cost of ray tracing, but adds to the complexity of tree update.This thesis proposes methods to cope with dynamic scenes in hardware-accelerated ray tracing, with focus on reducing traffic to external memory. Firstly, a hardware architecture is designed for linear bounding volume hierarchy construction, an algorithm which is a basic building block in most state-of-the-art software tree builders. The algorithm is rearranged into a streaming form which reduces traffic to one-third of software implementations of the same algorithm. Secondly, an algorithm is proposed for compressing bounding volume hierarchies in a streaming manner as they are output from a hardware builder, instead of performing compression as a postprocessing pass. As a result, with the proposed method, compression reduces the overall cost of tree update rather than increasing it. The last main contribution of this thesis is an evaluation of shallow bounding volume hierarchies, common in software ray tracing, for use in hardware pipelines. These are found to be more energy-efficient than binary hierarchies. The results in this thesis both confirm that dynamic scene support may become a bottleneck in real time ray tracing, and add to the state of the art on tree update in terms of energy-efficiency, as well as the complexity of scenes that can be handled in real time on resource-constrained platforms

    Bounding Volume Hierarchies for Collision Detection

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    In virtual environment world, performing collision detection between various 3D objects requires sophisticated steps to be followed in order to properly visualize their effect. It is challenging due to the fact that multiple objects undergo various motion depending on the application’s genre. It is however an essential challenge to be resolved since it’s many use in the computer animation, simulation and robotic industry. Thus, object intersection between rigid bodies has become one of the most important areas in order to bring realism to simulation and animation

    Otimização em GPU de bounding volume hierarchies para ray tracing

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    Orientador: Hélio PedriniDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: Métodos de Ray Tracing são conhecidos por produzir imagens extremamente realistas ao custo de um alto esforço computacional. Pouco após terem surgido, percebeu-se que a maior parte do custo associado a estes métodos está relacionada a encontrar a intersecção entre o grande número de raios que precisam ser traçados e a geometria da cena. Estruturas de dados especiais que indexam e organizam a geometria foram propostas para acelerar estes cálculos, de forma que apenas um subconjunto da geometria precise ser verificado para encontrar as intersecções. Dentre elas, podemos destacar as Bounding Volume Hierarchies (BVH), que são estruturas usadas para agrupar objetos 3D hierarquicamente. Recentemente, uma grande quantidade de esforços foi aplicada para acelerar a construção destas estruturas e aumentar sua qualidade. Este trabalho apresenta um novo método para a construção de BVHs de alta qualidade em sistemas manycore. O método em questão é uma extensão do atual estado da arte na construção de BVHs em GPU, Treelet Restructuring Bounding Volume Hierarchy (TRBVH), e consiste em otimizar uma árvore já existente reorganizando subconjuntos de seus nós através de uma abordagem de agrupamento aglomerativo. A implementação deste método foi feita para a arquitetura Kepler utilizando CUDA e foi testada em dezesseis cenas que são comumente usadas para avaliar o desempenho de estruturas aceleradoras. É demonstrado que esta implementação é capaz de produzir árvores com qualidade comparável às geradas utilizando TRBVH para aquelas cenas, além de ser 30% mais rápidaAbstract: Ray tracing methods are well known for producing very realistic images at the expense of a high computational effort. Most of the cost associated with those methods comes from finding the intersection between the massive number of rays that need to be traced and the scene geometry. Special data structures were proposed to speed up those calculations by indexing and organizing the geometry so that only a subset of it has to be effectively checked for intersections. One such construct is the Bounding Volume Hierarchy (BVH), which is a tree-like structure used to group 3D objects hierarchically. Recently, a significant amount of effort has been put into accelerating the construction of those structures and increasing their quality. We present a new method for building high-quality BVHs on manycore systems. Our method is an extension of the current state-of-the-art on GPU BVH construction, Treelet Restructuring Bounding Volume Hierarchy (TRBVH), and consists of optimizing an already existing tree by rearranging subsets of its nodes using an agglomerative clustering approach. We implemented our solution for the NVIDIA Kepler architecture using CUDA and tested it on sixteen distinct scenes that are commonly used to evaluate the performance of acceleration structures. We show that our implementation is capable of producing trees whose quality is equivalent to the ones generated by TRBVH for those scenes, while being about 30% faster to do soMestradoCiência da ComputaçãoMestre em Ciência da Computaçã

    Methods for fast construction of bounding volume hierarchies

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