Ragdoll
Physics-driven body for falls and knockdowns
Also known as: Ragdoll physics · Physics asset · Ragdoll Unreal · Ragdoll Unity · Death animation physics · Character physics body
Definition
A ragdoll is a character whose bones are driven by physics instead of animation, so the body falls, collapses and reacts to forces in a natural way. Each bone gets a simple collision shape and joint limits that connect it to the next, and the engine simulates them. In Unreal Engine this setup is the Physics Asset, and Unity has Ragdoll Wizard and joints. Ragdolls are used for deaths, knockdowns and hit reactions, and can blend with animation for partial effects.
In production
Set capsule sizes that fit the body without overlapping too much, and give joints realistic angle limits, so elbows and knees do not bend backward. Test falls from several heights and angles, and tune mass and damping. Switch from animation to ragdoll with a short blend to avoid a pop, and consider blending back after a knockdown. Physics bodies also serve as hit boxes for gameplay.
Tools that use Ragdoll
See also
Skeleton
Hierarchical bone structure for animation
Skeletal Mesh
Skinned mesh driven by a skeleton
Procedural Animation
Motion generated by rules and physics instead of keyframes
Rigging
Building a deformation skeleton
Collision Mesh
Simplified geometry used for physics
Animation Blending
Interpolate poses between clips