3D Rigging Systems: Wk11 Blend Shapes

There are two main methods of doing facial rigging, the first is using bones and SDKs in a similar manner to the hand and makes for a far more dynamic rig, however you can also use Blend shapes to assign quick emotions or basic controls to a face, since that is what we are aiming for the blend shapes seems to be the logical choice. Blend shapes work by moving vertices between two points, one is the default model position and the the other is the maximum extreme of what ever control you are attempting to make, for example when getting the eye brow to move up and down using a blend shape, the extreme point would be the highest point the eyebrow can move to, the blend shape then assigns all points in-between on a slider accessible in the Animation editor window in Maya.

One issue with blend shapes however is that by default a blend shape has influence over all vertices in a mesh, this means that when getting multiple blend shapes to act simultaneously, for example opening the mouth and raising the eyebrow at the same time. One or both of the controls will bug out and either not work properly or cause some horrific geometrical errors in the mesh. To solve this issue there is a tool called the membership edit tool in Maya that allows the user to deselect certain vertices from a blend shape control, for example removing the influence of the eyebrow control from the vertices controlling the shape of the mouth and vice versa.