RTSAH Traversal Order for Occlusion Rays

Thiago Ize, Charles Hansen

Research output: Chapter in Book/Report/Conference proceedingConference contribution

17 Scopus citations


We accelerate the finding of occluders in tree based acceleration structures, such as a packetized BVH and a single ray kd-tree, by deriving the ray termination surface area heuristic (RTSAH) cost model for traversing an occlusion ray through a tree and then using the RTSAH to determine which child node a ray should traverse first instead of the traditional choice of traversing the near node before the far node. We further extend RTSAH to handle materials that attenuate light instead of fully occluding it, so that we can avoid superfluous intersections with partially transparent objects. For scenes with high occlusion, we substantially lower the number of traversal steps and intersection tests and achieve up to 2× speedups. © 2010 The Author(s).
Original languageEnglish (US)
Title of host publicationComputer Graphics Forum
Number of pages9
StatePublished - Apr 28 2011
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-C1-016-04
Acknowledgements: This publication is based on work supported by Award No. KUS-C1-016-04, made by King Abdullah University of Science and Technology (KAUST), DOE VACET, NSF OCI0906379, and NSF CRI-0551724. Pete Shirley wrote code to compute the BVH RTSAH using Monte Carlo sampling. We are extremely grateful for the anonymous reviewer's suggestion to use form factors to solve the BVH RTSAH. The Mad Science scene is by Dan Konieczka and Giorgio Luciano; the Carnival by Dan Konieczka, the Bedroom was modeled by David Vacek and designed by David Tousek; all three scenes are available from the 3dRender. com Lighting Challenges. The Happy Buddha, Bunny, Dragon, and Armadillo are courtesy of the Stanford Computer Graphics Laboratory.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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