Attaching Softbody hair to Armature

Hey everyone,

I’m having a bit of trouble with my hair mesh. I enabled Softbody physics on it and gave it a Weight Painted Goal. This all works just fine and dandy, but now I want the hair to follow the bone controlling the position and rotation of the head. I’ve tried Bone Parenting, as well as Armature Parenting with Weight Painting, but it just starts to act weird. Am I missing something obvious?

As always: thanks in advance,

PS: Bonus question: Is there a way to scale a bone to it’s center, rather than it’s root?

Did you apply the Soft Body physics to the emitter mesh or to the hair particle strands? It should be the latter.

The method I’ve used sucessfully is to make the hair emitter mesh from a duplicate of the character model’s scalp, set up the hair particle systems, then make the resulting “wig” mesh a child of the head bone of the character armature – essentially the wig is following exactly the same motion as the top of the character’s head.

If you apply Soft Body physics to the emitter mesh, though, it will deform with every head move and totally screw up your parent particle strand orientations. The “scalp” of the wig should remain rigid, and only the hair strands move due to Soft Body.

Oops, I forgot to mention it’s mesh hair, not particles. Sorry! :o The wig idea for particles sound worth trying out sometime though.

Do you have the soft goal weighted to 0 at the root of the hair? The base of each hair strand mesh should not be affected by the softbody modifier at all, but instead be weighted to 1 for the head bone.

as for the bonus question, I don’t have blender infront of me, but if you scale a bone in edit mode it scales to the center doesn’t it? If you mean in pose mode, you could snap the cursor to the center of the bone with ctrl+s and then switch from median point to cursor.

Sorry myself, I assumed it was particle hair, probably shouldn’t have.

For some pointers on both types of hair, scan through my Kata thread (contains nudity) – I used both in this project, and somewhere in those pages I did mini-tutorials on both soft-body mesh hair (the first approach I used) and particle hair (the second and final approach).

The way you’ve constructed your hair mesh is pretty critical, so without seeing it it’s hard to be specific, but in general you’ll want to make the hair mesh a child of the same bone that moves the head. The Goal vertex group & the Goal settings in the S-B tab can be set to make parts of the mesh rigid, and other parts to move about under the physics sim – that’s probably where you want to look first for the kind of issue you describe.

@Asano: Thanks for your reply. The weight paint is applied correctly. Your tip for cursor scaling worked brilliantly, thanks! =)

@Chipmasque: Ha, I love your Kata thread! Been there multiple times before! I figured out the first half of my problem; it simply needed to be re-parented and have it’s cache cleared. This gave rise to a new problem though:
I want the body to deflect the hair, but as it’s already intersecting from the start it just goes haywire. I’ll look through your thread and play with it a bit. Thanks! =)

Yeah, that’ll do it. Any vertices “inside” the collision mesh will basically be trapped until “yanked out” rather forcefully, which usually doesn’t happen in soft-body sims. It’s very important to design the hair mesh so that all verts are initially outside the collision body .