Summary: EUROGRAPHICS 2008 / Steve Marschner and Michael Wimmer
Volume 27 (2008), Number 4
Sample Based Visibility for Soft Shadows
using Alias-free Shadow Maps
1Chalmers University of Technology, Sweden 2ARTIS-INRIA/Grenoble University, France
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.
Categories and Subject Descriptors (according to ACM CCS): I.3.7 [Computer Graphics]: Three-Dimensional
Graphics and Realism Shadowing