A Material Point Method For Snow Simulation – How Snow is Made for Disney’s Frozen

As part of the marketing for the release of Disney’s Frozen on November 27, 2013, the studio has shared a SIGGRAPH video describing their snow-making technology.

The video briefly demonstrates what is written in a white paper titled “A Material Point Method For Snow Simulation” developed by Alexey Stomakhin, Craig Schroedery, Lawrence Chai, Joseph Teran, and Andrew Selle. The white paper goes on to describe the difficulty of simulating snow, here’s the paper’s abstract:

Snow is a challenging natural phenomenon to visually simulate. While the graphics community has previously considered accumulation and rendering of snow, animation of snow dynamics has not been fully addressed. Additionally, existing techniques for solids and fluids have difficulty producing convincing snow results. Specifically, wet or dense snow that has both solid- and fluid-like properties is difficult to handle. Consequently, this paper presents a novel snow simulation method utilizing a usercontrollable elasto-plastic constitutive model integrated with a hybrid Eulerian/Lagrangian Material Point Method. The method is continuum based and its hybrid nature allows us to use a regular Cartesian grid to automate treatment of self-collision and fracture. It also naturally allows us to derive a grid-based semi-implicit integration scheme that has conditioning independent of the number of Lagrangian particles. We demonstrate the power of our method with a variety of snow phenomena including complex character interactions.

The simulation remarkably shows how subtle representations of wetness and density can have significant impacts on the dynamic nature of snow.