For three decades, 3D animation pipelines have struggled with cloth clipping through characters and objects. This bug forces studios to spend thousands of artist hours fixing frame-by-frame, while games ship with the flawed behavior. In late 2024, ZOZO published a physics solver that eliminates this persistent problem entirely.

Previous approaches relied on penalty forces or constraint projection, both fundamentally flawed. Penalty forces react after penetration occurs, while constraint projection fails to conserve energy properly. The 2020 Incremental Potential Contact (IPC) framework improved things by modeling collision as energy rather than force, using a logarithmic barrier that becomes infinitely large as surfaces approach zero distance.

However, IPC's logarithmic barrier creates numerical instability. Its curvature grows without bound as surfaces get close, making Newton's method ill-conditioned and requiring excessive iterations. ZOZO's breakthrough replaces the logarithm with a cubic polynomial that maintains bounded curvature, ramping up stiffness gradually instead of maxing out immediately. This prevents the condition number explosion that plagued previous methods.

The cubic barrier handles over 184 million simultaneous contact pairs without interpenetration, producing cloth that behaves like fabric rather than rubber or ghosts. Thin sheets stack properly with zero triangle invasion. The solver represents a fundamental mathematical improvement that could reshape physics simulation across the industry, from film VFX to real-time game graphics.