Fast 3D Diffusion for Scalable Granular Media Synthesis

TL;DR

This paper introduces a novel 3D diffusion-based generative pipeline that efficiently synthesizes large, realistic granular media assemblies, significantly reducing simulation times and enabling larger-scale DEM simulations.

Contribution

The paper presents a two-stage 3D diffusion and inpainting pipeline for scalable, realistic granular media synthesis, compatible with existing DEM workflows and capable of generating complex particle shapes.

Findings

Simulation time reduced from days to hours.

Able to generate over 200,000 particles efficiently.

Maintains mechanical consistency with traditional DEM simulations.

Abstract

Discrete Element Method (DEM) simulations of granular media are computationally intensive, particularly during initialization phases dominated by large displacements and kinetic energy. This paper presents a novel generative pipeline based on 3D diffusion models that directly synthesizes arbitrarily large granular assemblies in mechanically realistic configurations. The approach employs a two-stage pipeline. First, an unconditional diffusion model generates independent 3D voxel grids representing granular media; second, a 3D inpainting model, adapted from 2D techniques using masked inputs and repainting strategies, seamlessly stitches these grids together. The inpainting model uses the outputs of the unconditional diffusion model to learn from the context of adjacent generations and creates new regions that blend smoothly into the context region. Both models are trained on binarized 3D occupancy grids derived from a database of small-scale DEM simulations, scaling linearly with the number of output voxels. Simulations that spanned over days can now run in hours, practically enabling simulations containing more than 200k ballast particles. The pipeline remains fully compatible with existing DEM workflows as it post-processes the diffusion generated voxel grids into DEM compatible particle meshes. Being mechanically consistent on key granulometry metrics with the original DEM simulations, the pipeline is also compatible with many other applications in the field of granular media, with capability of generating both convex and non-convex particles. Showcased on two examples (railway ballast and lunar regolith), the pipeline reimagines the way initialization of granular media simulations is performed, enabling scales of generation previously unattainable with traditional DEM simulations.