April 2, 2024

A Lightweight Checklist for New MPM Projects

The guardrails I keep close before spinning up a new material point method experiment.

By Ziyin Qu

Whenever I begin a new MPM prototype, I fall back on a short checklist. It looks deceptively simple, but it prevents 90% of late-night debugging sessions.

1. Unit tests for interpolation

If the particle-to-grid and grid-to-particle transfers are not symmetric, the solver will explode long before any interesting physics happens. I keep two tests around: one for momentum conservation and one for angular momentum conservation. They run in milliseconds but catch almost every regression.

2. Mesh-quality monitors

Many collaborators care most about the resulting deformations, not the raw math. I stream the deformation gradient of hero particles to a simple UI so we can see when elements collapse. That small affordance builds trust and encourages the team to push more ambitious shots.

3. Shared notebooks

Publishing derivations in a shared notebook (I use Quarto) shortens onboarding for interns and industry partners. The notebook includes energy terms, pseudocode, and a gallery of failures. It is far easier to maintain than a sprawling design doc.

This routine mirrors what we emphasized during my internships at Meta and TikTok: move fast, but leave behind the breadcrumbs that make collaboration effortless.