Create a Reverse utility node.

Find the constraint node for the group and connect the Mouth_Top_W0 out node to the Reverse.inputX.

Now connect the Reverse.outputX to the Mouth_Bottom_W1 in node.

Check out the results. Type a value of 1 in the Mouth_Top_W0 attribute and Mouth_Bottom_W1 is now 0. Type a 0.8 and it become 0.2 and so on. Now that the first one is under control, proceed to set it up for the other seven (make sure you have the top level of the control group hierarchy picked, easiest through the Outliner). I made this task a little less tedious by writing a script called cfParentConstrain.mel that you can download from www.dirtyoldtoon.com/scripts. It sets up the parent constraint and automates the reverse node input/output. Once you've finished the job, rotate open the jaw and check your handiwork. The controls follow along, but they're floating halfway between the jaw and their original position. We'll have to weight the Parent constraint node to get a more satisfying effect.

Fig 12. Connections in the Hypergraph

Go through the control objects and change the Mouth_Top_W0 number until the mouth open shape looks natural This probably means that the top middle control is completely weighted to the head, (i.e. it doesn't move at all), the bottom middle control is completely weighted to the jaw, the two mouth corners are halfway at 0.5, and the rest are somewhere in between.

Now we'll drive the movement of the clusters with the bottom level of the control hierarchy through the exact same parent constraint method.

Grab the Mouth_top bone, then the Mouth_Bottom bone, then one of the "_group" control nodes.

Fig13. Cluster Weighting

Parent constrain each cluster to the two controls it lies between. In the example diagram, the highlighted cluster falls somewhere in between the corner control and the top lip control, so those will be the two parents. It's easiest to work on one group of clusters at a time and hide the rest, because there are several clusters that are going to be on top of each other and will be difficult to select.

 

Open up the jaw again and go through the process of weighting the cluster constraints 'till everything looks nice and purdy just like you did with the "group" nodes. All your lip controls are now set up and you're ready to begin the skinning process. That wasn't so bad was it?