Computer Graphics Forum

Sample Based Visibility for Soft Shadows using Alias-free Shadow Maps

Erik Sintorn, Elmar Eisemann, and Ulf Assarsson

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This paper introduces an accurate real-time soft shadow algorithm that uses sample based visibility. Initially, we present a GPU-based alias-free hard shadow map algorithm that typically requires only a single render pass from the light, in contrast to using depth peeling and one pass per layer. For closed objects, we also suppress the need for a bias. The method is extended to soft shadow sampling for an arbitrarily shaped area-/volumetric light source using 128-1024 light samples per screen pixel. The alias-free shadow map guarantees that the visibility is accurately sampled per screen-space pixel, even for arbitrarily shaped (e.g. non-planar) surfaces or solid objects. Another contribution is a smooth coherent shading model to avoid common light leakage near shadow borders due to normal interpolation.

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@article{bib:sintorn:2008,
    author       = { Sintorn, Erik and Eisemann, Elmar and Assarsson, Ulf },    
    title        = { Sample Based Visibility for Soft Shadows using Alias-free Shadow Maps },
    journal      = { Computer Graphics Forum },
    volume       = { 27 },
    year         = { 2008 },
    pages        = { 1285--1292 },
    doi          = { 10.1111/j.1467-8659.2008.01267.x },
    dblp         = { journals/cgf/SintornEA08 },
    url          = { https://publications.graphics.tudelft.nl/papers/616 },
}