32-Issue 4

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https://diglib.eg.org/handle/10.2312/182

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Browsing 32-Issue 4 by Subject "Color"

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    An Area-Preserving Parametrization for Spherical Rectangles
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Ureña, Carlos; Fajardo, Marcos; King, Alan; Nicolas Holzschuch and Szymon Rusinkiewicz
    We present an area-preserving parametrization for spherical rectangles which is an analytical function with domain in the unit rectangle [0;1]2 and range in a region included in the unit-radius sphere. The parametrization preserves areas up to a constant factor and is thus very useful in the context of rendering as it allows to map random sample point sets in [0;1]2 onto the spherical rectangle. This allows for easily incorporating stratified, quasi-Monte Carlo or other sampling strategies in algorithms that compute scattering from planar rectangular emitters.
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    Exponential Soft Shadow Mapping
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Shen, Li; Feng, Jieqing; Yang, Baoguang; Nicolas Holzschuch and Szymon Rusinkiewicz
    In this paper we present an image-based algorithm to render visually plausible anti-aliased soft shadows in real time. Our technique employs a new shadow pre-filtering method based on an extended exponential shadow mapping theory. The algorithm achieves faithful contact shadows by adopting an optimal approximation to exponential shadow reconstruction function. Benefiting from a novel overflow free summed area table tile grid data structure, numerical stability is guaranteed and error filtering response is avoided. By integrating an adaptive anisotropic filtering method, the proposed algorithm can produce high quality smooth shadows both in large penumbra areas and in high frequency sharp transitions, meanwhile guarantee cheap memory consumption and high performance.
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    Line-Sweep Ambient Obscurance
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Timonen, Ville; Nicolas Holzschuch and Szymon Rusinkiewicz
    Screen-space ambient occlusion and obscurance have become established methods for rendering global illumi- nation effects in real-time applications. While they have seen a steady line of refinements, their computational complexity has remained largely unchanged and either undersampling artefacts or too high render times limit their scalability. In this paper we show how the fundamentally quadratic per-pixel complexity of previous work can be reduced to a linear complexity. We solve obscurance in discrete azimuthal directions by performing line sweeps across the depth buffer in each direction. Our method builds upon the insight that scene points along each line can be incrementally inserted into a data structure such that querying for the largest occluder among the visited samples along the line can be achieved at an amortized constant cost. The obscurance radius therefore has no impact on the execution time and our method produces accurate results with smooth occlusion gradients in a few milliseconds per frame on commodity hardware.