Decapitated Blend Shapes for Facial Animation
Often you want to create blend shapes for the head of your model, but your head is part of the same mesh as the body. Creating blend shapes for the entire mesh is overkill and will slow things down as well. Here is a method to just create blend shapes for the head.
Decapitation
- Select the faces that make up the head (usually down to the collarbone)
- Make sure that Polygons Menu → Edit Mesh → Keep Faces Together is checked
- Select the option box for Polygons Menu → Mesh → Extract
- Make sure Separate Extracted Faces is checked
- Select the head, and duplicate it (Edit → Duplicate or CTRL-d). Move the new mesh out of the way. The pivot of the new mesh may actually be at the origin, you can use Modify → Center Pivot to make it easier to move the new base head. Do not modify the shape of this copy of the head, it will function as the new base shape.
Setting up the blend shapes
- Select the copy of the head and shift select the original head
- Go to Animation Menu → Create Deformers → Blend Shape. This is not the deformer you will use to animate, set the Weight to 1.
- Select the copy of the head
- Duplicate it (Edit → Duplicate or CTRL-d). and move the copy out of the way.
- Model this copy to have a different expression
- Select the second copy, shift select the first (undeformed) copy
- Go to Animation Menu → Create Deformers → Blend Shape. This is the deformer you will use to animate. If you adjust the Weight you will see both the other heads deform!
Re-attaching the head
- Select both the original head and the body
- Polygons Menu → Mesh → Combine
- Done!
Creating more heads to deform (more target shapes)
- Select the loose undeformed head (the first copy, the one with the blend shape deformer on it)
- Open up Windows → Animation Editors → Blend Shape
- Find the second blendshape controller (probably blendShape2, unless you renamed it to something more easily recognizable)
- Click the Add Base button
- Another copy of the head will be created, with the shape that is the result of the position of the slider for the first shape. A new slider will also appear, as this new copy is immediately set as target shape. You can move the new head to a convenient location and change the shape.