I expanded a little on the bounding box, and while I’ve moved on to learning shaders for the moment I’d really appreaciate some feedback and discussion on some of my methods. I think what someone else could potentially profit from is looking at the
projectFacePointsToFocalPlane() thing, I feel like figuring that out helped me the most (and probably will continue to do so in the future). As for the utility of using this for actual collision with the mouth - I saw @josh_beckwith saying he’d just use the center point and compare the distance. That makes a lot of sense to me and is probably the better solution, but I learned a lot from writing this and the projected points of the mouth features moving on the focal plane looks kinda neat.
Edit: I should also mention I started out with that bite-tutorial on Medium, https://medium.com/@Julien_He/game-in-spark-ar-part-1-1ddefdfa9838, so thanks for that and credit to Julien. The approach has changed a little over the course of the project however, so don’t expect this to work exactly the same or even similarly.