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Interactive Ray Tracing, 2008. RT 2008. IEEE Symposium on

Date 9-10 Aug. 2008

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Displaying Results 1 - 25 of 55
  • [Title page]

    Publication Year: 2008 , Page(s): i
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  • [Copyright notice]

    Publication Year: 2008 , Page(s): ii
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  • Contents

    Publication Year: 2008 , Page(s): iii - v
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  • Corporate supporters

    Publication Year: 2008 , Page(s): vi
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  • Message from the Chairs

    Publication Year: 2008 , Page(s): vii
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  • IEEE Visualization and Graphics Technical Committee (VGTC)

    Publication Year: 2008 , Page(s): viii
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  • Conference committee

    Publication Year: 2008 , Page(s): ix
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  • Portable software development for multi-core processors, many-core accelerators, and heterogeneous architectures

    Publication Year: 2008 , Page(s): x
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  • Ray tracing: Strengths and opportunities

    Publication Year: 2008 , Page(s): xi
    Cited by:  Papers (1)
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  • [Blank page]

    Publication Year: 2008 , Page(s): xii
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  • Papers

    Publication Year: 2008 , Page(s): xiii
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  • [Blank page]

    Publication Year: 2008 , Page(s): xiv
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  • Ray-specialized acceleration structures for ray tracing

    Publication Year: 2008 , Page(s): 3 - 10
    Cited by:  Papers (3)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (505 KB) |  | HTML iconHTML  

    The key to efficient ray tracing is the use of effective acceleration data structures. Traditionally, acceleration structures have been constructed under the assumption that rays approach from any direction with equal probability. However, we observe that for any particular frame the system has significant knowledge about the rays, especially eye rays and hard/soft shadow rays. In this paper we demonstrate that by using this information in conjunction with an appropriate acceleration structure - a set of one or more perspective grids - that ray tracing performance can be significantly improved over prior approaches. This acceleration structure can easily be rebuilt per frame, and provides significantly improved performance for rays originating at or near particular points such as the eye point and the light source(s), without sacrificing the ability to trace arbitrary rays. We demonstrate true real-time frame rates on a game-like scene rendered on an eight-core desktop PC at 1920times1200 resolution for primary visibility, and hard shadows, along with lower frame rates for Monte Carlo soft shadows. In particular, we demonstrate the fastest hard shadow ray-tracing results that we are aware of. We argue that the perspective grid acceleration structure provides insight into why the Z buffer algorithm is faster than traditional ray tracing and shows there is a useful continuum of visibility algorithms between the two traditional approaches. View full abstract»

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  • Adaptive acceleration structures in perspective space

    Publication Year: 2008 , Page(s): 11 - 17
    Cited by:  Papers (3)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (734 KB) |  | HTML iconHTML  

    Traversal efficiency of ray tracing acceleration structures can be improved by specializing them, each frame, for the rays that are traced in that frame. A companion paper to this one demonstrates that extremely high traversal performance for eye and hard shadow rays can be obtained by transforming rays and geometry with a perspective transform, then using a grid acceleration structure in the perspective space. However, the performance of this perspective grid acceleration structure suffers for off-axis rays such as those used for soft shadows or depth of field. In this paper we address this shortcoming by exploring the use of the perspective transform with adaptive acceleration structures such as kd-trees. The problem of choosing optimal split planes for an acceleration structure is different in perspective space than it is in world space, so we introduce a new cost metric for estimating traversal cost of acceleration structures in perspective space. This metric is related to the traditional surface area metric but defined in perspective space. We implement a ray-tracing system with both traditional and perspective acceleration structures and demonstrate significant performance improvements using the perspective space structures even when build time is included. Additionally we evaluate the effectiveness of our new cost metric compared to traditional cost metrics. A key insight demonstrated by these results is that end-to-end rendering performance can be improved by building a different specialized acceleration structure for each light and camera in the scene instead of using a single non-specialized acceleration structure for all rays. View full abstract»

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  • [Blank page]

    Publication Year: 2008 , Page(s): 18
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  • Raytracing prefiltered occlusion for aggregate geometry

    Publication Year: 2008 , Page(s): 19 - 26
    Cited by:  Papers (1)  |  Patents (3)
    Multimedia
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6113 KB) |  | HTML iconHTML  

    We prefilter occlusion of aggregate geometry, e.g., foliage or hair, storing local occlusion as a directional opacity in each node of a bounding volume hierarchy (BVH). During intersection, we terminate rays early at BVH nodes based on ray differential, and composite the stored opacities. This makes intersection cost independent of geometric complexity for rays with large differentials, and simultaneously reduces the variance of occlusion estimates. These two algorithmic improvements result in significant performance gains for soft shadows and ambient occlusion. The prefiltered opacity data depends only on geometry, not lights, and can be computed in linear time based on assumptions about the statistics of aggregate geometry. View full abstract»

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  • Row tracing using hierarchical occlusion maps

    Publication Year: 2008 , Page(s): 27 - 34
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3558 KB) |  | HTML iconHTML  

    A new rendering method that ray traces an entire row of the image at a time is introduced. This moves some of the ray tracing computations into a simplified 1D domain and reduces the memory requirements considerably. Visibility determination is performed efficiently using hierarchical occlusion maps and provides faster renderings than packet ray tracing in general and OpenGL for large scenes. In addition, the algorithm shows near perfect scaling when multi-threaded and works very well with kd-trees and octrees, as implementations demonstrate. Finally, optimal rendering times are reached with trees that are an order of magnitude smaller than those required for regular ray tracing. View full abstract»

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  • Multi bounding volume hierarchies

    Publication Year: 2008 , Page(s): 35 - 40
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1736 KB) |  | HTML iconHTML  

    Efficient tracing of single and incoherent rays is still a challenge in computer graphics. Coherent packet tracing has reached real-time performance, but ray packets bring about restrictions for the architecture of the renderer and their suitability for diverging secondary ray bundles is uncertain. The algorithm presented in this paper avoids these problems by not using ray packets at all. Instead, it uses triangle packets and bounding volume packets in a novel acceleration data structure called multi bounding volume hierarchy (MBVH). It is designed for SIMD single ray tracing. The hierarchy is built from a binary bounding volume hierarchy by collapsing subtrees of height two into SIMD nodes storing four bounding boxes. A modified cost function for construction guarantees that all but one of the leaf nodes contain exactly four triangles. The MBVH makes good use of data-level parallelism during traversal and triangle intersection, yielding speed-ups of up to 2.8times for random ray shooting. It consumes less memory than a regular bounding volume hierarchy and requires no modifications to the architecture of the rendering engine. View full abstract»

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  • Large ray packets for real-time Whitted ray tracing

    Publication Year: 2008 , Page(s): 41 - 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2482 KB) |  | HTML iconHTML  

    In this paper, we explore large ray packet algorithms for acceleration structure traversal and frustum culling in the context of Whitted ray tracing, and examine how these methods respond to varying ray packet size, scene complexity, and ray recursion complexity. We offer a new algorithm for acceleration structure traversal which is robust to degrading coherence and a new method for generating frustum bounds around reflection and refraction ray packets. We compare, adjust, and finally compose the most effective algorithms into a real-time Whitted ray tracer. With the aid of multi-core CPU technology, our system renders complex scenes with reflections, refractions, and/or point-light shadows anywhere from 4-20 FPS. View full abstract»

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  • Getting rid of packets - Efficient SIMD single-ray traversal using multi-branching BVHs -

    Publication Year: 2008 , Page(s): 49 - 57
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (14648 KB) |  | HTML iconHTML  

    While contemporary approaches to SIMD ray tracing typically rely on traversing packets of coherent rays through a binary data structure, we instead evaluate the alternative of traversing individual rays through a bounding volume hierarchy with a branching factor of 16. Though obviously less efficient than high-performance packet techniques for primary rays, we demonstrate that for less coherent secondary ray distributions this approach is at least competitive with (and often faster than) typical packet traversal techniques. View full abstract»

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  • [Blank page]

    Publication Year: 2008 , Page(s): 58
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  • Coherent ray tracing via stream filtering

    Publication Year: 2008 , Page(s): 59 - 66
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (7732 KB) |  | HTML iconHTML  

    We introduce an approach to coherent ray tracing based on a new stream filtering algorithm. This algorithm, which is motivated by breadth-first ray traversal and elimination of inactive ray elements, exploits the coherence exhibited by processing arbitrarily-sized groups of rays in SIMD fashion. These groups are processed by a series of filters that partition rays into active and inactive subsets throughout the various stages of the rendering process. We present results obtained with a detailed cycle-accurate simulation of a hardware architecture that supports wider-than-four SIMD processing and efficient scatter/gather memory and stream partitioning operations. In this context, stream filtering achieves frame rates of 15-25 fps for scenes of high geometric complexity rendered with path tracing and a variety of advanced visual effects. View full abstract»

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  • Improving Kd-tree quality at a reasonable construction cost

    Publication Year: 2008 , Page(s): 67 - 72
    Cited by:  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2437 KB) |  | HTML iconHTML  

    We consider construction of high-quality kd-tree and investigate the effect of techniques based on perfect splits. The main idea of perfect splits is clipping of objects straddling the splitting planes during the construction. This effectively results in reducing the number of references in leaves while also generating new potential split positions. We derive an efficient algorithm for triangle clipping/assignment and show how to avoid problems for parallel construction using clipping. Investigating the influence of using clipping results at different kd-tree construction stages, we finally come up with on-the-fly pruning algorithm that improves rendering performance by up to 25% decreasing construction time as well. View full abstract»

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  • Tree rotations for improving bounding volume hierarchies

    Publication Year: 2008 , Page(s): 73 - 76
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2230 KB) |  | HTML iconHTML  

    Current top-down algorithms for constructing bounding volume hierarchies (BVHs) using the surface area heuristic (SAH) rely on an estimate of the cost of the potential subtrees to determine how to partition the primitives. After a tree has been fully built, however, the true cost value at each node can be computed. We present two related algorithms that use this information to reduce the treepsilas total cost through a series of local adjustments (tree rotations) to its structure. The first algorithm uses a fast and simple hill climbing method and the second uses simulated annealing to obtain greater improvements by avoiding local minima. Both algorithms are easy to add to existing BVH implementations and are suitable for preprocessing static geometry for interactive ray tracing. View full abstract»

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  • Corrections to the surface area metric with respect to mail-boxing

    Publication Year: 2008 , Page(s): 77 - 80
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2432 KB) |  | HTML iconHTML  

    The surface area heuristic is the standard method for producing high quality acceleration structures for ray-tracing. High quality acceleration structures minimize per-ray costs for ray-tracing and thus rendering times. However, the metric used by the surface area heuristic makes several assumptions that do not hold in practice. Much work has been done to analyze these assumptions and provide a more accurate cost model but no-one has analyzed the surface area metricpsilas interaction with a common ray-tracing optimization, mail-boxing. We present a correction to the surface area metric for ray-tracing systems using mail-boxing. Additionally, we provide a concrete example of how our new metric improves the quality of kd-trees as compared to the original surface area metric. Finally, we show that our correction provides a noticeable (about 30%) reduction in the number of intersection tests performed during ray-tracing as well as improving run-time performance. We conclude that this algorithmic adjustment is so simple that anyone implementing mail-boxing should consider using it. View full abstract»

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