Mouth direction vector (Patreon)

Just a simple trick. Make sure the mesh has point normals first, then you group or blast away everything but one point on the top jaw and one on the lower jaw. With an add SOP, create a line in between the two points and then use a resample SOP so you get an additional point in the middle. As that point will inherit a mix of the end point normals, deleting the end points, you'll have a single point that is always in the middle of the mouth, no matter any animation or movement, including a vector pointing away from it - perfect as a base for a force for driving fire, smoke for breath in the winter, or as in the case of the picture above, as a base for a force to drive saliva cast off. :D

Example file: https://goo.gl/L8jNGN