but it is not JUST the shader its also some clever modeling/viseme configuration on my part. The shortest way I can explain what it is doing is something of a non-ZTested portal effect. For the mouth at least, there is a material set to a mask that simply hides the head material and reveals the mouth material sitting just behind it, and the visemes mainly control the shape and size of that mask to give the illusion of a mouth opening.
No, really it IS Poiyomi's toon shader. But to be more specific its using the stencil function that the shader provides. Though it is totally possible to modify other shaders to use Unity's stencil buffer. This is the chunk of relevant documentation -> https://docs.unity3d.com/Manual/SL-Stencil.html. While Poiyomi has this functionality by default I can hack existing shaders to use the buffer.
