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Thirteenth Eurographics Workshop on Rendering (2002) P. Debevec and S. Gibson (Editors)

Summary: Thirteenth Eurographics Workshop on Rendering (2002)
P. Debevec and S. Gibson (Editors)
Approximate Soft Shadows on Arbitrary Surfaces
using Penumbra Wedges
Tomas Akenine-Möller and Ulf Assarsson
Department of Computer Engineering, Chalmers University of Technology, Sweden
Shadow generation has been subject to serious investigation in computer graphics, and many clever algorithms
have been suggested. However, previous algorithms cannot render high quality soft shadows onto arbitrary, ani-
mated objects in real time. Pursuing this goal, we present a new soft shadow algorithm that extends the standard
shadow volume algorithm by replacing each shadow quadrilateral with a new primitive, called the penumbra
wedge. For each silhouette edge as seen from the light source, a penumbra wedge is created that approximately
models the penumbra volume that this edge gives rise to. Together the penumbra wedges can render images that
often are remarkably close to more precisely rendered soft shadows. Furthermore, our new primitive is designed
so that it can be rasterized efficiently. Many real-time algorithms can only use planes as shadow receivers, while
ours can handle arbitrary shadow receivers. The proposed algorithm can be of great value to, e.g., 3D computer
games, especially since it is highly likely that this algorithm can be implemented on programmable graphics hard-
ware coming out within the next year, and because games often prefer perceptually convincing shadows.
CR Categories: I.3.7 [Computer Graphics ] Three-Dimensional Graphics and Realism
Keywords: soft shadows, graphics hardware, shadow volumes.


Source: Assarsson, Ulf - Department of Computer Engineering, Chalmers University of Technology


Collections: Computer Technologies and Information Sciences