Physics-Based Animation

We introduce an Eulerian liquid simulation framework based on the Voronoi diagram of a potentially unorganized collection of pressure samples. Constructing the simulation mesh in this way allows us to place samples anywhere in the computational domain; we exploit this by choosing samples that accurately capture the geometry and topology of the liquid surface. When combined with high-resolution explicit surface tracking this allows us to simulate nearly arbitrarily thin features, while eliminating noise and other artifacts that arise when there is a resolution mismatch between the simulation and the surface—and allowing a precise inclusion of surface tension based directly on and at the same resolution as the surface mesh. In addition, we present a simplified Voronoi/Delaunay mesh velocity interpolation scheme, and a direct extension of embedded free surfaces and solid boundaries to Voronoi meshes.

Matching Fluid Simulation Elements to Surface Geometry and Topology

Physics-related papers from SCA 2006. The full list is available here, courtesy of Kesen-Huang.

• Detail-Preserving Fluid Control
• Keyframe control of complex particle systems using the adjoint method
• A Controllable, Fast and Stable Basis for Vortex Based Smoke Simulation
• Path-Based Control of Smoke Simulations
• Geometric, Variational Integrators for Computer Animation
• Fast Arbitrary Splitting of Deforming Objects
• Fast Simulation of Deformable Models in Contact Using Dynamic Deformation Textures
• Simultaneous Coupling of Fluids and Deformable Bodies
• Oriented Strands – Dynamics of Stiff Multi-body System
• Simple Linear Bending Stiffness in Particle Systems
• A Consistent Bending Model for Cloth Simulation with Corotational Subdivision Finite Elements
• Animation of Open Water Phenomena with coupled Shallow Water and Free Surface Simulations
• Modeling Ice Dynamics As A Thin-Film Stefan Problem
• Generating Surface Crack Patterns
• Physically based Boiling Simulation
• Simulation of Bubbles
• Practical Animation of Turbulent Splashing Water

Physics-oriented papers from Eurographics 2008.

• A Semi-Lagrangian CIP Fluid Solver without Dimensional Splitting
• A Fast Simulation Method Using Overlapping Grids for Interactions between Smoke and Rigid Objects
• An Adaptive Contact Model for the Robust Simulation of Knots
• Fluid in Video: Augmenting Real Video with Simulated Fluids

Short papers:

• Identification of Dynamic Mass Spring Parameters for Deformable Body Simulation

Still filling in some older collections… Kesen maintains a complete list here.

• Legendre Fluids: A Unified Framework for Analytic Reduced Space Modeling and Rendering of Participating Media
• A Simple Boiling Module
• CORDE: Cosserat Rod Elements for the Dynamic Simulation of One-Dimensional Elastic Objects
• Arbitrary cutting of deformable tetrahedralized objects
• Hybrid Simulation of Deformable Solids
• Cubic Shells
• Time-critical distributed contact for 6-DoF haptic rendering of adaptively sampled reduced deformable models
• Adaptive Deformations with Fast Tight Bounds
• Real-time Simulations of Bubbles and Foam within a Shallow Water Framework
• Animation of Chemically Reactive Fluids Using a Hybrid Simulation Method
• Weakly Compressible SPH for Free Surface Flows
• Liquid Simulation on Lattice-Based Tetrahedral Meshes
• Solving General Shallow Wave Equations on Surfaces

Looking backwards again… Kesen’s full page is here.

• Linear-Time Super-Helices
• Physically Guided Animation of Trees
• Wind Projection Basis for Real-Time Animation of Trees
• Mixing Fluids and Granular Materials
• Hydraulic Erosion Using Smoothed Particle Hydrodynamics
• Simulation of two-phase flow with sub-scale droplet and bubble effects
• Scalable Real-Time Animation of Rivers
• Implicit Contact Handling for Deformable Objects
• Continuum-based Strain Limiting

I noticed today that I’d catalogued physics papers from conferences between 2007 and the present, and that Simon Clavet had catalogued a large number of physics papers from various conferences prior to 2006, with some going back as far as 1992.  So in the interests of completeness, I thought I’d fill in a list for SIGGRAPH 2006.   Clearly Kesen maintains a more thorough list covering all of graphics, but I sometimes find it helpful to see just the physics ones alone.  (I might add a few of the other conferences/years I’ve missed at some point as well.)

• Efficient Simulation of Large Bodies of Water by Coupling Two and Three Dimensional Techniques
• Multiple Interacting Liquids
• Fluid Animation with Dynamic Meshes
• Model Reduction for Real-Time Fluids
• Resolving Surface Collisions Through Intersection Contour Minimization
• Super-Helices for Predicting the Dynamics of Natural Hair
• Fast Proximity Computation Among Deformable Models using Discrete Voronoi Diagrams

Physics papers from Eurographics 2007:

• Real-Time Simulation of Thin Shells
• A Finite Element Method on Convex Polyhedra
• Textured Liquids with the Marker Level Set

When simulating fluids, tetrahedral methods provide flexibility and ease of adaptivity that Cartesian grids find difficult to match. However, this approach has so far been limited by two conflicting requirements. First, accurate simulation requires quality Delaunay meshes and the use of circumcentric pressures. Second, meshes must align with potentially complex moving surfaces and boundaries, necessitating continuous remeshing. Unfortunately, sacrificing mesh quality in favour of speed yields inaccurate velocities and simulation artifacts. We describe how to eliminate the boundary-matching constraint by adapting recent embedded boundary techniques to tetrahedra, so that neither air nor solid boundaries need to align with mesh geometry. This enables the use of high quality, arbitrarily graded, non-conforming Delaunay meshes, which are simpler and faster to generate. Temporal coherence can also be exploited by reusing meshes over adjacent timesteps to further reduce meshing costs. Lastly, our free surface boundary condition eliminates the spurious currents that previous methods exhibited for slow or static scenarios. We provide several examples demonstrating that our efficient tetrahedral embedded boundary method can substantially increase the flexibility and accuracy of adaptive Eulerian fluid simulation.

Tetrahedral Embedded Boundary Methods for Accurate and Flexible Adaptive Fluids

Smoke animations are hard to art-direct because simple changes in parameters such as simulation resolution often lead to unpredictable changes in the final result. Previous work has addressed this problem with a guiding approach which couples low-resolution simulations – that exhibit the desired flow and behaviour – to the final, high-resolution simulation. This is done in such a way that the desired low frequency features are to some extent preserved in the high-resolution simulation. However, the steady (i.e. constant) guiding used often leads to a lack of sufficiently high detail, and employing time-dependent guiding is expensive because the matrix of the resulting set of equations needs to be recomputed at every iteration. We propose an improved mathematical model for Eulerian-based simulations which is better suited for dynamic, time-dependent guiding of smoke animations through a novel variational coupling of the low- and high-resolution simulations. Our model results in a matrix that does not require re-computation when the guiding changes over time, and hence we can employ time-dependent guiding more efficiently both in terms of storage and computational requirements. We demonstrate that time-dependent guiding allows for more high frequency detail to develop without losing correspondence to the low resolution simulation. Furthermore, we explore various artistic effects made possible by time-dependent guiding.

Improved Variational Guiding of Smoke Animations

This paper presents a physically based method for simulating the heat transfers between the different environmental elements to synthesize realistic winter sceneries. We simulate the snow fall over the ground, as well as the conductive, convective and radiative thermal transfers using a finite volume method according to the variations of air and dew point temperatures, the amount of snow, cloud cover and day-night cycles. Our approach takes into account phase changes such as snow melting into water or water freezing into ice.

Heat Transfer Simulation for Modeling Realistic Winter Sceneries