39 research outputs found
Circumventing volumetric locking in explicit material point methods: A simple, efficient, and general approach
The material point method (MPM) is frequently used to simulate large
deformations of nearly incompressible materials such as water, rubber, and
undrained porous media. However, MPM solutions to nearly incompressible
materials are susceptible to volumetric locking, that is, overly stiff behavior
with erroneous strain and stress fields. While several approaches have been
devised to mitigate volumetric locking in the MPM, they require significant
modifications of the existing MPM machinery, often tailored to certain basis
functions or material types. In this work, we propose a locking-mitigation
approach featuring an unprecedented combination of simplicity, efficacy, and
generality for a family of explicit MPM formulations. The approach combines the
assumed deformation gradient () method with a
volume-averaging operation built on the standard particle-grid transfer scheme
in the MPM. Upon explicit time integration, this combination yields a new and
simple algorithm for updating the deformation gradient, preserving all other
MPM procedures. The proposed approach is thus easy to implement, low-cost, and
compatible with the existing machinery in the MPM. Through various types of
nearly incompressible problems in solid and fluid mechanics, we verify that the
proposed approach efficiently circumvents volumetric locking in the explicit
MPM, regardless of the basis functions and material types
Efficient Learning of Mesh-Based Physical Simulation with BSMS-GNN
Learning the physical simulation on large-scale meshes with flat Graph Neural
Networks (GNNs) and stacking Message Passings (MPs) is challenging due to the
scaling complexity w.r.t. the number of nodes and over-smoothing. There has
been growing interest in the community to introduce \textit{multi-scale}
structures to GNNs for physical simulation. However, current state-of-the-art
methods are limited by their reliance on the labor-intensive drawing of coarser
meshes or building coarser levels based on spatial proximity, which can
introduce wrong edges across geometry boundaries. Inspired by the bipartite
graph determination, we propose a novel pooling strategy, \textit{bi-stride} to
tackle the aforementioned limitations. Bi-stride pools nodes on every other
frontier of the breadth-first search (BFS), without the need for the manual
drawing of coarser meshes and avoiding the wrong edges by spatial proximity.
Additionally, it enables a one-MP scheme per level and non-parametrized pooling
and unpooling by interpolations, resembling U-Nets, which significantly reduces
computational costs. Experiments show that the proposed framework,
\textit{BSMS-GNN}, significantly outperforms existing methods in terms of both
accuracy and computational efficiency in representative physical simulations.Comment: Updates summary: * update to the accepted version ICM
TPA-Net: Generate A Dataset for Text to Physics-based Animation
Recent breakthroughs in Vision-Language (V&L) joint research have achieved
remarkable results in various text-driven tasks. High-quality Text-to-video
(T2V), a task that has been long considered mission-impossible, was proven
feasible with reasonably good results in latest works. However, the resulting
videos often have undesired artifacts largely because the system is purely
data-driven and agnostic to the physical laws. To tackle this issue and further
push T2V towards high-level physical realism, we present an autonomous data
generation technique and a dataset, which intend to narrow the gap with a large
number of multi-modal, 3D Text-to-Video/Simulation (T2V/S) data. In the
dataset, we provide high-resolution 3D physical simulations for both solids and
fluids, along with textual descriptions of the physical phenomena. We take
advantage of state-of-the-art physical simulation methods (i) Incremental
Potential Contact (IPC) and (ii) Material Point Method (MPM) to simulate
diverse scenarios, including elastic deformations, material fractures,
collisions, turbulence, etc. Additionally, high-quality, multi-view rendering
videos are supplied for the benefit of T2V, Neural Radiance Fields (NeRF), and
other communities. This work is the first step towards fully automated
Text-to-Video/Simulation (T2V/S). Live examples and subsequent work are at
https://sites.google.com/view/tpa-net