I have a character with a hair particle system. When I animate the character and render using the Cycles engine, a hair particle will stretch from the scalp mesh to the mesh object’s origin point in random frames (most frames render correctly, only 1 in 7 or 1 in 8 contains the error).
The particle system emits from a scalp object that has no subdivision surface and no other modifiers apart form the armature. I have tried regenerating the hair and restyling, but the problem persists. Here’s a picture of the error (the yellow line originating from the scalp is a hair particle):
I have attached the stripped-down .blend file with just the scalp, the rigify rig, the hair particle system, and some lights.
The character is pretty standard. The only complex element it has is a spline IK ear which targets a soft-body curve. However, I have tried removing all scalp vertices from the ear bone vertex groups, and the problem still appears in the render.
I’m hoping there’s something that can be tweaked in the settings; I’ve been trying for weeks to resolve it. Thanks for any help you can provide.
You still have scalp vertices influenced by neck bone vertex group.
But removing vertices from this vertex group was not sufficient.
Interpolated children may have problems since 2.74 changes when using clumping.
It looks like few interpolated children particles are going crazy for a step of motion blur.
And it looks like it is still related to vertex groups of the armature.
So, I just deleted armature modifier and used head bone as parent of your scalp mesh.
And it works. No mesh deformation = no interpolated child particle going crazy.