A Hierarchical Shadow Volume Algorithm

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Date
2004
Journal Title
Journal ISSN
Volume Title
Publisher
The Eurographics Association
Abstract
The shadow volume algorithm is a popular technique for real-time shadow generation using graphics hardware. Its major disadvantage is that it is inherently fillrate-limited, as the performance is inversely proportional to the area of the projected shadow volumes. We present a new algorithm that reduces the shadow volume rasterization work significantly. With our algorithm, the amount of per-pixel processing becomes proportional to the screenspace length of the visible shadow boundary instead of the projected area. The first stage of the algorithm finds 8×8 pixel tiles, whose 3D bounding boxes are either completely inside or outside the shadow volume. After that, the second stage performs per-pixel computations only for the potential shadow boundary tiles. We outline a twopass implementation, and also describe an efficient single-pass hardware architecture, in which the two stages are separated using a delay stream. The only modification required in applications is a new pair of calls for marking the beginning and end of a shadow volume. In our test scenes, the algorithm processes up to 11.5 times fewer pixels compared to current state-of-the-art methods, while reducing the external video memory bandwidth by a factor of up to 17.1.
Description

        
@inproceedings{
:10.2312/EGGH/EGGH04/015-024
, booktitle = {
Graphics Hardware
}, editor = {
Tomas Akenine-Moeller and Michael McCool
}, title = {{
A Hierarchical Shadow Volume Algorithm
}}, author = {
Aila, Timo
and
Akenine-Möller, Tomas
}, year = {
2004
}, publisher = {
The Eurographics Association
}, ISSN = {
1727-3471
}, ISBN = {
3-905673-15-0
}, DOI = {
/10.2312/EGGH/EGGH04/015-024
} }
Citation