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 "ambient obscurance"

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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.