Blender Git Commit Log

Child strand deformation based on parent motion states when reading from
caches.

This allows child strands to follow the motion of parent strands as
calculated by the hair simulation. Unlike the particle system path
caching, this method does not regenerate all the children every frame.
Instead, it relies on an initial child setup that defines the base
shape, then applies the parent motion as a weighted linear deformation.

The result is in fact the same as with regular particle clumping, kink,
roughness etc.. Particles also take care to not change the child shape
when the parent moves, but this is not formalized anywhere (which makes
changing particle code quite difficult). So ignoring the particle code
is both permissible and efficient.