KawaiiPhysics is an Unreal Engine physics plugin that provides a skeletal mesh simulation tool for calculating pseudo-physics bone sway. It is designed to create natural movement for hair and clothing by controlling bone rotation based on stiffness and damping without requiring a full rigid body physics engine.
The system features a character physics constraint framework and a runtime controller that allows for the dynamic adjustment of simulation parameters and external forces. It utilizes data-asset preset management to ensure consistent physics behavior across different characters and objects.
The project covers secondary motion simulation, including bone chain dynamics and the application of external forces like wind and gravity. It manages mesh penetration through primitive-based collision detection using spheres, capsules, and planes, alongside distance-based bone constraints to maintain skeletal integrity. To ensure stability, the simulation includes state filtering to prevent glitches during teleportation or rotation spikes.