Category: Uncategorized

SIGGRAPH Asia 2016

Versatile Interactions at Interfaces for SPH-Based Simulations

Tao Yang, Ming C. Lin, Ralph R. Martin, Jian Chang, and Shi-Min Hu

The realistic capture of various interactions at interfaces is a challenging problem for SPH-based simulation. Previous works have mainly considered a single type of interaction, while real-world phenomena typically exhibit multiple interactions at different interfaces. For instance, when cracking an egg, there are simultaneous interactions between air, egg white, egg yolk, and the shell. To conveniently handle all interactions simultaneously in a single simulation, a versatile approach is critical. In this paper, we present a new approach to the surface tension model based on pairwise interaction forces; its basis is to use a larger number of neighboring particles. Our model is stable, conserves momentum, and furthermore, prevents the particle clustering problem which commonly occurs at the free surface. It can be applied to simultaneous interactions at multiple interfaces (e.g. fluid-solid and fluid-fluid). Our method is versatile, physically plausible and easy-to-implement. We also consider the close connection between droplets and bubbles, and show how to animate bubbles in air as droplets, with the help of a new surface particle detection method. Examples are provided to demonstrate the capabilities and effectiveness of our approach.

Versatile Interactions at Interfaces for SPH-Based Simulations

SCA 2016 papers

Simulation-related papers from Symposium on Computer Animation 2016:

SIGGRAPH 2016

SIGGRAPH 2016 papers:

 

TOG presentations at SIGGRAPH 2016:

Boundary detection in particle-based fluids

Marcos Sandim, Douglas Cedrim, Luis Gustavo Nonato, Paulo Pagliosa, and Afonso Paiva

This paper presents a novel method to detect free-surfaces on particle-based volume representation. In contrast to most particle-based free-surface detection methods, which perform the surface identification based on physical and geometrical properties derived from the underlying fluid flow simulation, the proposed approach only demands the spatial location of the particles to properly recognize surface particles, avoiding even the use of kernels. Boundary particles are identified through a Hidden Point Removal (HPR) operator used for visibility test. Our method is very simple, fast, easy to implement and robust to changes in the distribution of particles, even when facing large deformation of the free-surface. A set of comparisons against state-of-the-art boundary detection methods show the effectiveness of our approach. The good performance of our method is also attested in the context of fluid flow simulation involving free-surface, mainly when using level-sets for rendering purposes.

Boundary detection in particle-based fluids

CAMA: Contact-Aware Matrix Assembly with Unified Collision Handling for GPU-based Cloth Simulation

Min Tang, Huamin Wang, Le Tang, Ruofeng Tong, Dinesh Manocha

We present a novel GPU-based approach to robustly and efficiently simulate high-resolution and complexly layered cloth. The key component of our formulation is a parallelized matrix assembly algorithm that can quickly build a large and sparse matrix in a compressed format and accurately solve linear systems on GPUs. We also present a fast and integrated solution for parallel collision handling, including collision detection and response computations, which utilizes spatio-temporal coherence. We combine these algorithms as part of a new cloth simulation pipeline that incorporates contact forces into implicit time integration for collision avoidance. The entire pipeline is implemented on GPUs, and we evaluate its performance on complex benchmarks consisting of 100-300K triangles. In practice, our system takes a few seconds to simulate one frame of a complex cloth scene, which represents significant speedups over prior CPU and GPU-based cloth simulation systems.

CAMA: Contact-Aware Matrix Assembly with Unified Collision Handling for GPU-based Cloth Simulation

Eurographics 2016

Eurographics 2016, in Lisbon Portugal, will feature the following physics-related papers:

SIGGRAPH Asia 2015

SIGGRAPH Asia 2015:

 

TOG papers:

SCA 2015

Symposium on Computer Animation, 2015 edition: Illuminating Ideas!

Nonlinear Material Design Using Principal Stretches

Hongyi Xu, Funshing Sin, Yufeng Zhu, Jernej Barbic

The Finite Element Method is widely used for solid deformable object simulation in film, computer games, virtual reality and medicine. Previous applications of nonlinear solid elasticity employed materials from a few standard families such as linear corotational, nonlinear St.Venant-Kirchhoff, Neo-Hookean, Ogden or Mooney-Rivlin materials. However, the spaces of all nonlinear isotropic and anisotropic materials are infinite-dimensional and much broader than these standard materials. In this paper, we demonstrate how to intuitively explore the space of isotropic and anisotropic nonlinear materials, for design of animations in computer graphics and related fields. In order to do so, we first formulate the internal elastic forces and tangent stiffness matrices in the space of the principal stretches of the material. We then demonstrate how to design new isotropic materials by editing a single stress-strain curve, using a spline interface. Similarly, anisotropic (orthotropic) materials can be designed by editing three curves, one for each material direction. We demonstrate that modifying these curves using our proposed interface has an intuitive, visual, effect on the simulation. Our materials accelerate simulation design and enable visual effects that are difficult or impossible to achieve with standard nonlinear materials.

Nonlinear Material Design Using Principal Stretches