How to convert rigged character poses to shape keys?

Question

Is it possible to use a rigged characters poses to create shape keys?

I am attempting to create 52 blend shapes, for my characters face…

1. I create the first shape key (bases).

2. I open pose mode and move a few bones to create the first blend shape (Eye Blink Left).

Then open object mode, and select character mesh, and open the modifier tab, and save shape key in the armature modifier.

Then I go to the vertex tab and change the value of the shape key (Eye Blink Left) from 0 to 1; to see if the shape key has been applied.

It has… However, when the value is at 1 the jaw gets bloated, and the arms of the character move slightly, as well.

Every following shape key I make, has the same result.

I’ve checked the weight painting and the rig is fine on that end… So what else can be the issue?

Answer 1

I should take a look at the file to be sure, but probably thoose unwanted vertices shift are due to bone constraints: when you switch the armature from edit mode to pose mode all bone constraints get activated: expecially IK chains, Stretch to, Dumped track and similar constraints can cause little (or even big) shift of parented vertices, that get recorded in the shape key when applying the modifier. This shift should be noticeable when you switch the armature from Pose Position to Rest Position (see image).

A couple of methods to solve:

• turn off the bone constraints that cause the shift (copy IK pose to FK and use it during the shape key creation phase)

• In edit mode select the shape key, select all vertices that should stay still, go to vertex menu > Blend from shape; press F9 to open the dialog black box and select basis shape key, 1.0 as blend and uncheck the Add option. In this way all selected vertices will be stored in the location of the basis shape key (and will not move when the shape key is activated).