Month: July 2011

Procedural Fluid Modeling of Explosion Phenomena Based on Physical Properties

Genichi Kawada, Takashi Kanai

We propose a method to procedurally model the fluid flows of explosion phenomena by taking physical properties into account. Explosion flows are always quite difficult to control, because they easily disturb each other and change rapidly. With this method, the target flows are described by control paths, and the propagation flows are controlled by following these paths. We consider the physical properties, which are the propagations of the pressure generated by the ignition, the detonation state caused by the pressure and the fuel combustions. Velocity, density, temperature and pressure fields are generated procedurally, and the fluid flows are computed from these four fields based on grid-based fluid simulations. Using this method, we can achieve a fluid motion that closely resembles one generated solely through simulation. This method realizes the modeling of flows controlled frame by frame and follows the flow’s physical properties.

Procedural Fluid Modeling of Explosion Phenomena Based on Physical Properties

A Simple Finite Volume Method for Adaptive Viscous Liquids

Christopher Batty, Ben Houston

We present the first spatially adaptive Eulerian fluid animation method to support challenging viscous liquid effects such as folding, coiling, and variable viscosity. We propose a tetrahedral node-based embedded finite volume method for fluid viscosity, adapted from popular techniques for Lagrangian deformable objects. Applied in an Eulerian fashion with implicit integration, this scheme stably and efficiently supports high viscosity fluids while yielding symmetric positive definite linear systems. To integrate this scheme into standard tetrahedral mesh-based fluid simulators, which store normal velocities on faces rather than velocity vectors at nodes, we offer two methods to reconcile these representations. The first incorporates a mapping between different degrees of freedom into the viscosity solve itself. The second uses a FLIP-like approach to transfer velocity data between nodes and faces before and after the linear solve. The former offers tighter coupling by enabling the linear solver to act directly on the face velocities of the staggered mesh, while the latter provides a sparser linear system and a simpler implementation. We demonstrate the effectiveness of our approach with animations of spatially varying viscosity, realistic rotational motion, and viscous liquid buckling and coiling.

A Simple Finite Volume Method for Adaptive Viscous Liquids

Robust Real-Time Deformation of Incompressible Surface Meshes

Raphael Diziol, Jan Bender, Daniel Bayer

We introduce an efficient technique for robustly simulating incompressible objects with thousands of elements in real-time. Instead of considering a tetrahedral model, commonly used to simulate volumetric bodies, we simply use their surfaces. Not requiring hundreds or even thousands of elements in the interior of the object enables us to simulate more elements on the surface, resulting in high quality deformations at low computation costs. The elasticity of the objects is robustly simulated with a geometrically motivated shape matching approach which is extended by a fast summation technique for arbitrary triangle meshes suitable for an efficient parallel computation on the GPU. Moreover, we present an oscillation-free and collision-aware volume constraint, purely based on the surface of the incompressible body. The novel heuristic we propose in our approach enables us to conserve the volume, both globally and locally. Our volume constraint is not limited to the shape matching method and can be used with any method simulating the elasticity of an object. We present several examples which demonstrate high quality volume conserving deformations and compare the run-times of our CPU implementation, as well as our GPU implementation with similar methods.

Robust Real-Time Deformation of Incompressible Surface Meshes

Graph-based Fire Synthesis

Yubo Zhang, Carlos Correa, Kwan-Liu Ma

We present a novel graph-based data-driven technique for cost-effective fire modeling. This technique allows composing long animation sequences using a small number of short simulations. While traditional techniques such as motion graphs and motion blending work well for character motion synthesis, they cannot be trivially applied to fluids to produce results with physically consistent properties which are crucial to the visual appearance of fluids. Motivated by the motion graph technique used in character animations, we introduce a new type of graph which can be applied to create various fire phenomena. Each graph node consists of a group of compact spatialtemporal flow pathlines instead of a set of volumetric state fields. Consequently, achieving smooth transitions between discontinuous graph nodes for modeling turbulent fires becomes feasible and computationally efficient.The synthesized particle flow results allow direct particle controls which is much more flexible than a full volumetric representation of the simulation output. The accompanying video shows the versatility and potential power of this new technique for synthesizing realtime complex fire at the quality comparable to production animations.

Graph-based Fire Synthesis

SCA 2011

The draft program for SCA 2011 is online here. Ke-Sen Huang maintains links to the full set of papers here.  Many of the papers involve physical simulation, including: