A former Pixar FX Technical Director explains how his Multi-Layered RBD Simulation workflow lets Houdini artists add fractures and secondary detail while preserving approved destruction motion.

Full interview and research.

Destruction simulations can become extremely expensive to revise once their overall movement has been approved. Changing the fracture pattern or behavior of one area may alter piece indexing, constraints, collisions, and the motion of surrounding geometry, forcing artists to recalculate work that a director already liked. Former Pixar FX Technical Director Jae Jun Yi developed a layered Houdini workflow intended to make those increasingly specific production notes easier to address.

Presented at SIGGRAPH 2026, Multi-Layered RBD (Rigid Body Dynamics) Simulation begins with a relatively simple base simulation focused on composition and large-scale motion. Artists can then select individual pieces manually or through conditions such as size, velocity, impact strength, and collision events. Those pieces are fractured again, inherit the approved movement of their parents, and transition into a new dynamic simulation only when an artist-defined trigger is reached.

In this interview, Yi explains how identifiers, transform attributes, activation states, constraints, and collision adjustments maintain physical continuity between layers. He also discusses the workflow’s art-direction controls, its limitations for highly interconnected or interactive destruction, and his preference for extending Houdini’s familiar RBD toolset rather than creating a specialized system that other artists would struggle to understand.