They are called ‘Joystick’ controls – well that’s what I know it as but it probably has other names too.
Basically it’s like a joystick. You move this thing here, and that thing over there does something.
There’s no coding – it’s drivers hooked up to fire when a control is moved in a certain direction. That’s if the mesh is using shape keys.
If it’s using bones, then it would most likely be done with action constraints (ie – play an action when a control translates this way) but it could also be done with other constraints (depends on the needs)
You can have a look at the 2D baker rig in the lip sync course to see how this works – but there’s no videos on how to build it.
Essentially I am just driving the visibility of the mouth shape based on the location of the control.
https://cgcookie.com/courses/demystifying-lip-sync-animation-in-blender
hope that helps.
.
