Blender's particle system is quite brittle. Once particle hair has been created, we must not change the vertex numbers of the emitter mesh, e.g. by adding or deleting vertices. Or by merging geografts with the body.
Here we have loaded Genesis 8 Female with the standard Mohawk hair and genitals. Everything looks fine until we merge the genitals to the body with Merge Geografts.
Disaster! The hair has left the skull and is all over the place.
In the development version there is now a fix for this problem. In the global settings dialog, enable Postpone Hair Creation, which prevents hair from being generated when the scene is imported.
Import the character again. This time she is bald, but information about the hair is secretly stored inside the mesh. We can now merge the body and the genitals as usual.
Finally, when all changes have been made that can change vertex number, we press Restore Strand Hair. This button is located in the Finishing section, and after Merge Geografts, since it must be done afterwards. The hair information stored inside the mesh is now converted into real hair.
The Restore Strand Hair tool is only enabled if the active mesh contains unused hair information. Once the hair has been built, that information is cleared and the tool is disabled.
