The Uncanny Bevel.
Most likely, you’ve seen The Polar Express. The animation technique used in it resulted in animation that is said to result in the Uncanny Valley effect. The Uncanny Valley theory says that while human-acting robots/animations or other non-human reenactments can very closely mimic the actions of a human, they cannot truly portray the emotion of the human face. The resulting coldness or unemotionality evokes a strange feeling in observers, who will find the character to be insensitive, unmoving, or sometimes…