Spring bone
Bones driven by a simple spring and damper so hair, tails and straps sway after the motion without full physics.
Simulating hair or a long tail with real collision physics is expensive and easy to get wrong. Spring bones cheat: each bone hangs on a spring toward its rest position with a damper to settle the swing, often Verlet-integrated. When the character moves the bones lag and swing back — secondary motion for almost nothing.
The technique is central to anime-styled games and to formats like VRM and MMD, where that slightly exaggerated sway is part of the look. It's no replacement for ragdoll or cloth simulation, just a cheap way to give stiff rigs some life.