I have created a few different mouth shapes but I can’t seem to figure out how to have smooth interpolation between these shapes. It seems it can only be stepped (meaning on or off) with no morphing to next shape. Is it possible to have a smooth transition to next shape?
There is no morphing in Toon Boom Studio.
you can either add extra in-between shape between key mouth shape but I usually makes extra shapes for L and D sound other than basic 8 mouth shape for lip sync. And then extend shape for extra mouth shape such as bigger or smaller for happiness and sadness as different expressions needed based on the basic mouth shape. And then do the cell swapping while scrubbing. That works on me.
Studio does motion interpolation but not animation interpolation. If you research the difference you might be able to come up with a way to do what you want. The key is sort of like realizing you are a fish and not a rabbit. To get from A to Z you swim instead of hop. Whatever is involved in swimming could be used to look like a hop.