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Summary: Improved Ray Hierarchy Alias Free Shadows
Technical Report 2011:09
ISSN 1652-926X
Ola Olsson and Ulf Assarsson
May 6, 2011
Abstract
In this article, we introduce and evaluate several new algorithmic improve-
ments to Ray Hierarchies. The improved algorithm is used to produce ray-traced
shadows for omni-directional lights in fully dynamic environments. The new al-
gorithmic improvements increase culling rate of the traversal algorithm, in some
cases dramatically cutting the number of visited nodes. To evaluate performance,
we present a GPU implementation using CUDA, which uses a hybrid breadth-
depth algorithm to perform the traversal using bounded memory. The results show
that the use of improved cone hierarchies is able to produce high quality shadows
quickly for some scenes in real-time.
1 Introduction
Shadows, it is well known, are very important for visual fidelity in computer generated
images. The most popular algorithm for real-time shadows is shadow mapping, owing
to its flexibility and high performance. This technique, while fast, suffers from various
forms of aliasing [SD02] and are limited to a single plane of projection. It also requires
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