High-Performance Graphics 2011

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https://diglib.eg.org/handle/10.2312/324

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Browsing High-Performance Graphics 2011 by Subject "and texture"

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    The Alchemy Screen-Space Ambient Obscurance Algorithm
    (ACM, 2011) McGuire, Morgan; Osman, Brian; Bukowski, Michael; Hennessy, Padraic; Carsten Dachsbacher and William Mark and Jacopo Pantaleoni
    Ambient obscurance (AO) produces perceptually important illumination effects such as darkened corners, cracks, and wrinkles; proximity darkening; and contact shadows. We present the AO algorithm from the Alchemy engine used at Vicarious Visions in commercialgames. It is based on a new derivation of screen-space obscurance for robustness, and the insight that a falloff function can cancel terms in a visibility integral to favor efficient operations. Alchemy creates contact shadows that conform to surfaces, capturesobscurance from geometry of varying scale, and provides four intuitive appearance parameters: world-space radius and bias, and aesthetic intensity and contrast. The algorithm estimates obscurance at a pixel from sample points read from depth and normal buffers. It processes dynamic scenes at HD 720p resolution in about 4.5 ms on Xbox 360 and 3 ms onNVIDIA GeForce580.
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    Depth Buffer Compression for Stochastic Motion Blur Rasterization
    (ACM, 2011) Andersson, Magnus; Hasselgren, Jon; Akenine-Moeller, Tomas; Carsten Dachsbacher and William Mark and Jacopo Pantaleoni
    Previous depth buffer compression schemes are tuned for compressing depths values generated when rasterizing static triangles. They provide generous bandwidth usage savings, and are of great importance to graphics processors. However, stochastic rasterizationfor motion blur and depth of field is becoming a reality even for real-time graphics, and previous depth buffer compression algorithms fail to compress such buffers due to the irregularity of the positions and depths of the rendered samples. Therefore, we presenta new algorithm that targets compression of scenes rendered with stochastic motion blur rasterization. If possible, our algorithm fits a single time-dependent predictor function for all the samples in a tile. However, sometimes the depths are localized in more than onelayer, and we therefore apply a clustering algorithm to split the tile of samples into two layers. One time-dependent predictor function is then created per layer. The residuals between the predictor and the actual depths are then stored as delta corrections. For scenes with moderate motion, our algorithm can compress down to 65% compared to 75% for the previously best algorithm for stochastic buffers.
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    Voxelized Shadow Volumes
    (ACM, 2011) Wyman, Chris; Carsten Dachsbacher and William Mark and Jacopo Pantaleoni
    Efficient shadowing algorithms have been sought for decades, but most shadow research focuses on quickly identifying shadows on surfaces. This paper introduces a novel algorithm to efficiently sample light visibility at points inside a volume. These voxelized shadow volumes (VSVs) extend shadow maps to allow efficient, simultaneous queries of visibility along view rays, or can alternately be seen as a discretized shadow volume. We voxelize the scene intoa binary, epipolar-space grid where we apply a fast parallel scan to identify shadowed voxels. Using a view-dependent grid, our GPU implementation looks up 128 visibility samples along any eye ray with a single texture fetch. We demonstrate our algorithm in the context of interactive shadows in homogeneous, single-scattering participating media.