Interesting papers on SIGGRAPH 2005 Korea University Computer Graphics Lab.

Jin-Kyung Hong

A Vortex Particle Method for Smoke, Water and Explosions Andres Sell (Stanford University and Intel Corporation) Nick Rasmussen (Industrial Light & Magic) Ron Fedkiw (Stanford University and Industrial Light & Magic)

Summary • Keywords – Vortex methods, fluids, smoke, water, explosions • Highly turbulent effects – Grid based method • Uniform or octree grid – Vortex particle method • Eliminate dissipation, Increase details – Vorticity forcing • Grid based velocity field towards the desired vorticity 3

Results (1/2) • Turbulence in water flowing (320x128x320) 4

Results (2/2) • Smoke explosion (180x260x180) 5

Animating Gases with Hybrid Meshes Bryan E. Feldman James F. O’Brien Bryan M. Klingner (University of California, Berkeley)

Overview (1/2) • Keywords – Natural phenomena, physically based animation, CFD 7

Overview (2/2) • Animating gases – on unstructured tetrahedral meshes – the interaction of the fluids with irregularly shaped obstacles • Hybrid mesh – Combine tetrahedral cells with regular hexahedral cells • Naturally suited to behavior at curved or angled boundaries – Accuracy near obstacles – Efficiency in open regions 8

Method (1/2) • Discretization – Regular grids smoothly joined to irregular tetrahedral 9

Method (2/2) • Accelerations due to Body Forces – Gravity, vorticity confinement • Semi-Lagrangian integration • Mass Conservation – Open boundary, closed boundary • Interpolation – Regular hexahedral cells – Tetrahedral and transition cells 10

• Results 11

Animating Sand as a Fluid Yongning Zhu Robert Bridson

Summary • Keywords – Sand, water, animation, physical simulation • Existing fluid solver  granular materials • Sand modeling – Friction • Fluid simulation • Surface reconstruction from particles 13

Results (1/3) • As water and as sand (100x100x100) < with zero boundary friction > 14

Results (2/3) • Compare to previous one – Friction coefficient • between the sand and other objects • e.g. solid wall boundaries < with a boundary friction coeff. = 0.6 > 15

FLIP vs. PIC • FLIP: Fluid Implicit-Particle – Small-scale velocities preserved – Inviscid flows, water • PIC: Particle-in-Cell – Smoothed away – Viscous flows, sand 16

Results (3/3) • Granular material (100x60x60) 17