A technical sketch presented in the Fluids and Level Sets session at SIGGRAPH 2003

Modeling Complex Occlusions in Fluid Simulations
A Unified Level Set-Based Approach

Ben Houston
Exocortex Technologies, Inc
ben @ exocortex.org
Chris Bond
Frantic Films
cbond @ franticfilms.com
Mark Wiebe
Frantic Films
mwiebe @ franticfilms.com

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Other SIGGRAPH / ACM TOG sketches & publications:
Hierarchical RLE Level Set: A Compact and Versatile Deformable Surface Representation (ACM TOG January 2006)
Visual Simulation of Wispy Smoke - A particle-based and multi-resolution approach (SIGGRAPH 2005)
Gigantic Deformable Surfaces - a novel level set data structure combining DT-Grid and RLE features (SIGGRAPH 2005)
RLE Sparse Level Sets - a fast and scalable implicit surface representation (SIGGRAPH 2004)
The Tar Monster - creating a character with fluid simulation (SIGGRAPH 2004)
Clara.io: Online 3D editor (another of my projects)



A few recent papers, [Enright, Marschner & Fedkiw 2002; Foster & Fedkiw 2001; Foster & Metaxas 1996], have described the development of a computational fluid dynamics simulation method useful for computer graphics. We have implemented a system based on these papers, and propose an extension that augments and simplifies the handling of occlusions (impermeable solid objects). In the referenced papers, occlusions are treated differently based on whether or not they are moving, and discussion of how to deal with complex occlusions efficiently is minimal. The technique we have developed unifies the treatment of static and dynamic objects, and is able to better represent fluid-occlusion interactions at the low simulation resolutions used.

Our contribution consists of two parts.  The first part involves representing the occlusions via an augmented level set instead of the usual polygon based representations.  The second aspect of our contribution consists of a technique called constrained velocity extrapolation, which uses the occlusions level set representation to better capture the subtle effects the occlusions have on the behavior of surrounding fluid.  In addition to just more accurate fluid-occlusion interactions the above techniques allow for our arbitrarily shaped, moving occlusions (such as the two cups above) to act as containers for the fluid.


Houston, B., Bond, C., & M. Wiebe.  (2003)  "A unified approach for modeling complex occlusions in fluid simulations."  Proceedings of the SIGGRAPH 2003 conference on Sketches & Applications.  ACM Press. [PDF]


   author = {Ben Houston and Chris Bond and Mark Wiebe},
   title = {A unified approach for modeling complex occlusions in fluid simulations},
   booktitle = {Proceedings of the SIGGRAPH 2003 conference on Sketches \& applications},
   year = {2003},
   location = {San Diego, California},
   doi = {http://doi.acm.org/10.1145/965400.965561},
   publisher = {ACM Press},


More information available on the ACM Digital Library page for this sketch.

This research was supported in part by NRC IRAP Grant #482564.